working memory

The term "working memory" was coined by Miller, Galanter, and Pribram,{{cite book | vauthors = Pribram KH, Miller GA, Galanter E |title=Plans and the structure of behavior |publisher=Holt, Rinehart and Winston |location=New York |year=1960 |pages=[https://archive.org/details/plansstructureo00mill/page/65 65] |isbn=978-0-03-010075-8 |oclc=190675 |url-access=registration |url=https://archive.org/details/plansstructureo00mill/page/65 }}{{cite journal | vauthors = Baddeley A | title = Working memory: looking back and looking forward | journal = Nature Reviews. Neuroscience | volume = 4 | issue = 10 | pages = 829–839 | date = October 2003 | pmid = 14523382 | doi = 10.1038/nrn1201 | s2cid = 3337171 }} and was used in the 1960s in the context of theories that likened the mind to a computer. In 1968, Atkinson and Shiffrin{{cite book |title=Human Memory: A Proposed System and its Control Processes |vauthors=Atkinson RC, Shiffrin RM |publisher=Academic Press |year=1968 |isbn=978-0-12-543302-0 |veditors=Spence KW, Spence JT |series=Psychology of Learning and Motivation |volume=8 |pages=89–195 |doi=10.1016/S0079-7421(08)60422-3 |oclc=185468704 |s2cid=22958289 |url=https://escholarship.org/uc/item/2qq391s9 }} used the term to describe their "short-term store". The term short-term store was the name previously used for working memory. Other suggested names were short-term memory, primary memory, immediate memory, operant memory, and provisional memory.{{cite book | vauthors = Fuster JM |title=The prefrontal cortex: anatomy, physiology, and neuropsychology of the frontal lobe |publisher=Lippincott-Raven |location=Philadelphia |year=1997 |isbn=978-0-397-51849-4 |oclc=807338522 }}{{Page needed|date=September 2010}} Short-term memory is the ability to remember information over a brief period (in the order of seconds). Most theorists today use the concept of working memory to replace or include the older concept of short-term memory, marking a stronger emphasis on the notion of manipulating information rather than mere maintenance.{{citation needed|date=July 2022}}

The earliest mention of experiments on the neural basis of working memory can be traced back to more than 100 years ago, when Hitzig and Ferrier described ablation experiments of the prefrontal cortex (PFC); they concluded that the frontal cortex was important for cognitive rather than sensory processes.{{Cite book| vauthors = Fuster J |title= The prefrontal cortex |page= 126 |url= https://books.google.com/books?id=zuZlvNICdhUC&pg=PT140 |edition= 4th |year= 2008 |publisher= Elsevier |location= Oxford, UK |isbn= 978-0-12-373644-4}} In 1935 and 1936, Carlyle Jacobsen and colleagues were the first to show the deleterious effect of prefrontal ablation on delayed response.{{Cite book| vauthors = Benton AL | veditors = Levin HS, Eisenberg HM, Benton AL |title= Frontal lobe function and dysfunction|chapter-url= https://books.google.com/books?id=9b1htO0V0rwC&q=Jacobsen%20%20prefrontal%20ablation&pg=PA19|year= 1991|publisher= Oxford University Press|location= New York|isbn= 978-0-19-506284-7|page= 19|chapter= The prefrontal region:Its early history}}

Numerous models have been proposed for how working memory functions, both anatomically and cognitively. Of those, the two that have been most influential are summarized below.

{{Main|Baddeley's model of working memory}}

File:Baddeley and Hitch's Working Memory Model.png

In 1974 Baddeley and Hitch{{cite book | vauthors = Baddeley AD, Hitch G | title = Working Memory | volume = 2 | veditors = Bower GH | series = Psychology of Learning and Motivation | publisher = Academic Press | year = 1974 | pages = 47–89 | isbn = 978-0-12-543308-2 |oclc = 777285348 |doi= 10.1016/S0079-7421(08)60452-1}} introduced the multicomponent model of working memory. The theory proposed a model containing three components: the central executive, the phonological loop, and the visuospatial sketchpad with the central executive functioning as a control center of sorts, directing info between the phonological and visuospatial components.{{cite book |last1=Levin |first1=Eden S. |title=Working Memory: Capacity, Developments, and Improvement Techniques |date=2011 |publisher=Nova Science Publisher |isbn=978-1-61761-980-9 }}{{pn|date=July 2024}} The central executive is responsible for, among other things, directing attention to relevant information, suppressing irrelevant information and inappropriate actions, and coordinating cognitive processes when more than one task is simultaneously performed. A "central executive" is responsible for supervising the integration of information and for coordinating subordinate systems responsible for the short-term maintenance of information. One subordinate system, the phonological loop (PL), stores phonological information (that is, the sound of language) and prevents its decay by continuously refreshing it in a rehearsal loop. It can, for example, maintain a seven-digit telephone number for as long as one repeats the number to oneself repeatedly.{{Cite book|title = Variations in psychology| vauthors = Weiten S |publisher = Wadsworth|year = 2013|location = New York|pages = 281–282|edition = 9th }} The other subordinate system, the visuospatial sketchpad, stores visual and spatial information. It can be used, for example, for constructing and manipulating visual images and for representing mental maps. The sketchpad can be further broken down into a visual subsystem (dealing with such phenomena as shape, colour, and texture), and a spatial subsystem (dealing with location).{{citation needed|date=July 2022}}

In 2000 Baddeley extended the model by adding a fourth component, the episodic buffer, which holds representations that integrate phonological, visual, and spatial information, and possibly information not covered by the subordinate systems (e.g., semantic information, musical information). The episodic buffer is also the link between working memory and long-term memory.{{Cite book|title = Variations in psychology| vauthors = Weiten W |publisher = Wadsworth|year = 2013|location = Belmont, CA|pages = 281–282|edition = 9th}} The component is episodic because it is assumed to bind information into a unitary episodic representation. The episodic buffer resembles Tulving's concept of episodic memory, but it differs in that the episodic buffer is a temporary store.{{cite journal | vauthors = Baddeley A | title = The episodic buffer: a new component of working memory? | journal = Trends in Cognitive Sciences | volume = 4 | issue = 11 | pages = 417–423 | date = November 2000 | pmid = 11058819 | doi = 10.1016/S1364-6613(00)01538-2 | s2cid = 14333234 | doi-access = free }}

{{Annotated image|caption=The central executive of working memory is retrieving memory from long-term memory.|image=WorkingMemory Label Free.jpg|width=320|height=179|image-width=320|image-left=0|image-top=0|annotations={{Annotation|130|15|Central Executive|font-weight=bold|font-size=10}}

{{Annotation|10|160|Long-term Memory|font-weight=bold|font-size=10}}}}Anders Ericsson and Walter Kintsch{{cite journal | vauthors = Ericsson KA, Kintsch W | title = Long-term working memory | journal = Psychological Review | volume = 102 | issue = 2 | pages = 211–245 | date = April 1995 | pmid = 7740089 | doi = 10.1037/0033-295X.102.2.211 | name-list-style = amp }} have introduced the notion of "long-term working memory", which they define as a set of "retrieval structures" in long-term memory that enable seamless access to the information relevant for everyday tasks. In this way, parts of long-term memory effectively function as working memory. In a similar vein, Cowan does not regard working memory as a separate system from long-term memory. Representations in working memory are a subset of representations in long-term memory. Working memory is organized into two embedded levels. The first consists of long-term memory representations that are activated. There can be many of these—there is theoretically no limit to the activation of representations in long-term memory. The second level is called the focus of attention. The focus is regarded as having a limited capacity and holds up to four of the activated representations.{{cite book | vauthors =Cowan N |title=Attention and memory: an integrated framework |publisher=Oxford University Press |location=Oxford [Oxfordshire] |year=1995 |isbn=978-0-19-506760-6 |oclc=30475237 }}{{Page needed|date=September 2010}}

Oberauer has extended Cowan's model by adding a third component—a more narrow focus of attention that holds only one chunk at a time. The one-element focus is embedded in the four-element focus and serves to select a single chunk for processing. For example, four digits can be held in mind at the same time in Cowan's "focus of attention". When the individual wishes to perform a process on each of these digits—for example, adding the number two to each digit—separate processing is required for each digit since most individuals cannot perform several mathematical processes in parallel.{{Cite journal|title = Attention, working memory, and long-term memory in multimedia learning: A integrated perspective based on process models of working memory| vauthors = Schweppe J |date = 2014|journal = Educational Psychology Review|doi = 10.1007/s10648-013-9242-2|issue = 2|volume = 26|page = 289|s2cid = 145088718}} Oberauer's attentional component selects one of the digits for processing and then shifts the attentional focus to the next digit, continuing until all digits have been processed.{{cite journal | vauthors = Oberauer K | title = Access to information in working memory: exploring the focus of attention | journal = Journal of Experimental Psychology: Learning, Memory, and Cognition | volume = 28 | issue = 3 | pages = 411–421 | date = May 2002 | pmid = 12018494 | doi = 10.1037/0278-7393.28.3.411 }}

Working memory is widely acknowledged as having limited capacity. An early quantification of the capacity limit associated with short-term memory was the "magical number seven" suggested by Miller in 1956.{{cite journal | vauthors = Miller GA | title = The magical number seven plus or minus two: some limits on our capacity for processing information | journal = Psychological Review | volume = 63 | issue = 2 | pages = 81–97 | date = March 1956 | pmid = 13310704 | doi = 10.1037/h0043158 | s2cid = 15654531 }} Republished: {{cite journal | vauthors = Miller GA | title = The magical number seven, plus or minus two: some limits on our capacity for processing information. 1956 | journal = Psychological Review | volume = 101 | issue = 2 | pages = 343–352 | date = April 1994 | pmid = 8022966 | doi = 10.1037/0033-295X.101.2.343 | hdl-access = free | hdl = 11858/00-001M-0000-002C-4646-B }} Miller claimed that the information-processing capacity of young adults is around seven elements, referred to as "chunks", regardless of whether the elements are digits, letters, words, or other units. Later research revealed this number depends on the category of chunks used (e.g., span may be around seven for digits, six for letters, and five for words), and even on features of the chunks within a category. For instance, attention span is lower for longer words than short words. In general, memory span for verbal contents (digits, letters, words, etc.) depends on the phonological complexity of the content (i.e., the number of phonemes, the number of syllables),{{Cite journal| vauthors = Service E |date=1998-05-01|title=The Effect of Word Length on Immediate Serial Recall Depends on Phonological Complexity, Not Articulatory Duration|journal=The Quarterly Journal of Experimental Psychology Section A|volume=51|issue=2|pages=283–304|doi=10.1080/713755759|s2cid=220062579|issn=0272-4987}} and on the lexical status of the contents (whether the contents are words known to the person or not).{{Cite journal| vauthors = Hulme C, Roodenrys S, Brown G, Mercer R |date=November 1995 |title=The role of long-term memory mechanisms in memory span |journal=British Journal of Psychology |volume=86 |issue=4 |pages=527–36 |doi=10.1111/j.2044-8295.1995.tb02570.x}} Several other factors affect a person's measured span, and therefore it is difficult to pin down the capacity of short-term or working memory to a number of chunks. Nonetheless, Cowan proposed that working memory has a capacity of about four chunks in young adults (and fewer in children and old adults).{{cite journal | vauthors = Cowan N | title = The magical number 4 in short-term memory: a reconsideration of mental storage capacity | journal = The Behavioral and Brain Sciences | volume = 24 | issue = 1 | pages = 87–185 | date = February 2001 | pmid = 11515286 | doi = 10.1017/S0140525X01003922 | doi-access = free }}

In the visual domain, some investigations report no fixed capacity limit with respect to the total number of items that can be held in working memory. Instead, the results argue for a limited resource that can be flexibly shared between items retained in memory (see below in Resource theories), with some items in the focus of attention being allocated more resource and recalled with greater precision.{{cite journal | vauthors = Ma WJ, Husain M, Bays PM | title = Changing concepts of working memory | journal = Nature Neuroscience | volume = 17 | issue = 3 | pages = 347–356 | date = March 2014 | pmid = 24569831 | pmc = 4159388 | doi = 10.1038/nn.3655 }}{{cite journal | vauthors = Bays PM, Catalao RF, Husain M | title = The precision of visual working memory is set by allocation of a shared resource | journal = Journal of Vision | volume = 9 | issue = 10 | pages = 7.1–711 | date = September 2009 | pmid = 19810788 | pmc = 3118422 | doi = 10.1167/9.10.7 }}{{cite journal | vauthors = Bays PM, Gorgoraptis N, Wee N, Marshall L, Husain M | title = Temporal dynamics of encoding, storage, and reallocation of visual working memory | journal = Journal of Vision | volume = 11 | issue = 10 | pages = 6 | date = September 2011 | pmid = 21911739 | pmc = 3401684 | doi = 10.1167/11.10.6 }}{{cite journal | vauthors = Brady TF, Konkle T, Alvarez GA | title = A review of visual memory capacity: Beyond individual items and toward structured representations | journal = Journal of Vision | volume = 11 | issue = 5 | pages = 4 | date = May 2011 | pmid = 21617025 | pmc = 3405498 | doi = 10.1167/11.5.4 }}

Whereas most adults can repeat about seven digits in correct order, some individuals have shown impressive enlargements of their digit span—up to 80 digits. This feat is possible by extensive training on an encoding strategy by which the digits in a list are grouped (usually in groups of three to five) and these groups are encoded as a single unit (a chunk). For this to succeed, participants must be able to recognize the groups as some known string of digits. One person studied by Ericsson and his colleagues, for example, used an extensive knowledge of racing times from the history of sports in the process of coding chunks: several such chunks could then be combined into a higher-order chunk, forming a hierarchy of chunks. In this way, only some chunks at the highest level of the hierarchy must be retained in working memory, and for retrieval the chunks are unpacked. That is, the chunks in working memory act as retrieval cues that point to the digits they contain. Practicing memory skills such as these does not expand working memory capacity proper: it is the capacity to transfer (and retrieve) information from long-term memory that is improved, according to Ericsson and Kintsch (1995; see also Gobet & Simon, 2000{{cite journal | vauthors = Gobet F | title = Some shortcomings of long-term working memory | journal = British Journal of Psychology | volume = 91 | issue = Pt 4 | pages = 551–570 | date = November 2000 | pmid = 11104178 | doi = 10.1348/000712600161989 | url = http://bura.brunel.ac.uk/handle/2438/807 | type = Submitted manuscript }}).

Working memory capacity can be tested by a variety of tasks. A commonly used measure is a dual-task paradigm, combining a memory span measure with a concurrent processing task, sometimes referred to as "complex span". Daneman and Carpenter invented the first version of this kind of task, the "reading span", in 1980.{{Cite journal| vauthors = Daneman M, Carpenter PA |date=August 1980 |title=Individual differences in working memory and reading |journal=Journal of Verbal Learning & Verbal Behavior |volume=19 |issue=4 |pages=450–66 |doi=10.1016/S0022-5371(80)90312-6|s2cid=144899071 }} Subjects read a number of sentences (usually between two and six) and tried to remember the last word of each sentence. At the end of the list of sentences, they repeated back the words in their correct order. Other tasks that do not have this dual-task nature have also been shown to be good measures of working memory capacity.{{Cite journal| vauthors = Oberauer K, Süß HM, Schulze R, Wilhelm O, Wittmann WW |date=December 2000|title=Working memory capacity—facets of a cognitive ability construct|journal=Personality and Individual Differences|volume=29|issue=6|pages=1017–45|doi=10.1016/S0191-8869(99)00251-2 |s2cid=143866158 }} Whereas Daneman and Carpenter believed that the combination of "storage" (maintenance) and processing is needed to measure working memory capacity, we know now that the capacity of working memory can be measured with short-term memory tasks that have no additional processing component.{{cite journal | vauthors = Unsworth N, Engle RW | title = On the division of short-term and working memory: an examination of simple and complex span and their relation to higher order abilities | journal = Psychological Bulletin | volume = 133 | issue = 6 | pages = 1038–1066 | date = November 2007 | pmid = 17967093 | doi = 10.1037/0033-2909.133.6.1038 }}{{Cite journal| vauthors = Colom R, Abad FJ, Quiroga MÁ, Shih PC, Flores-Mendoza C |year=2008|title=Working memory and intelligence are highly related constructs, but why?|journal=Intelligence|volume=36|issue=6|pages=584–606|doi=10.1016/j.intell.2008.01.002}} Conversely, working memory capacity can also be measured with certain processing tasks that do not involve maintenance of information.{{Cite journal |vauthors = Oberauer K, Süß HM, Wilhelm O, Wittman WW |year=2003 |title=The multiple faces of working memory – storage, processing, supervision, and coordination |doi=10.1016/s0160-2896(02)00115-0 |journal=Intelligence |volume=31 |issue=2 |pages=167–193 |s2cid=14083639 |url=https://www.zora.uzh.ch/id/eprint/97155/1/intelligence.pdf}}{{cite journal | vauthors = Chuderski A | title = The relational integration task explains fluid reasoning above and beyond other working memory tasks | journal = Memory & Cognition | volume = 42 | issue = 3 | pages = 448–463 | date = April 2014 | pmid = 24222318 | pmc = 3969517 | doi = 10.3758/s13421-013-0366-x }} The question of what features a task must have to qualify as a good measure of working memory capacity is a topic of ongoing research.

Recently, several studies of visual working memory have used delayed response tasks. These use analogue responses in a continuous space, rather than a binary (correct/incorrect) recall method, as often used in visual change detection tasks. Instead of asking participants to report whether a change occurred between the memory and probe array, delayed reproduction tasks require them to reproduce the precise quality of a visual feature, e.g. an object's location, orientation or colour. In addition, the combination of visual perception such as within objects and colors can be used to improve memory strategy through elaboration, thus creating reinforcement within the capacity of working memory.{{cite journal |last1=Sobrinho |first1=Nuno D. |last2=Souza |first2=Alessandra S. |title=The interplay of long-term memory and working memory: When does object-color prior knowledge affect color visual working memory? |journal=Journal of Experimental Psychology: Human Perception and Performance |date=February 2023 |volume=49 |issue=2 |pages=236–262 |doi=10.1037/xhp0001071 |pmid=36480376 |hdl=10216/147912 |url=https://psyarxiv.com/8a2jw/ |hdl-access=free }}

Measures of working-memory capacity are strongly related to performance in other complex cognitive tasks, such as reading comprehension, problem solving, and with measures of intelligence quotient.{{cite journal | vauthors = Conway AR, Kane MJ, Engle RW | title = Working memory capacity and its relation to general intelligence | journal = Trends in Cognitive Sciences | volume = 7 | issue = 12 | pages = 547–552 | date = December 2003 | pmid = 14643371 | doi = 10.1016/j.tics.2003.10.005 | s2cid = 9943197 }}

Some researchers have argued{{cite journal | vauthors = Engle RW, Tuholski SW, Laughlin JE, Conway AR | title = Working memory, short-term memory, and general fluid intelligence: a latent-variable approach | journal = Journal of Experimental Psychology. General | volume = 128 | issue = 3 | pages = 309–331 | date = September 1999 | pmid = 10513398 | doi = 10.1037/0096-3445.128.3.309 | s2cid = 1981845 }} that working-memory capacity reflects the efficiency of executive functions, most notably the ability to maintain multiple task-relevant representations in the face of distracting irrelevant information; and that such tasks seem to reflect individual differences in the ability to focus and maintain attention, particularly when other events are serving to capture attention. Both working memory and executive functions rely strongly, though not exclusively, on frontal brain areas.{{cite journal | vauthors = Kane MJ, Engle RW | title = The role of prefrontal cortex in working-memory capacity, executive attention, and general fluid intelligence: an individual-differences perspective | journal = Psychonomic Bulletin & Review | volume = 9 | issue = 4 | pages = 637–671 | date = December 2002 | pmid = 12613671 | doi = 10.3758/BF03196323 | doi-access = free }}

Other researchers have argued that the capacity of working memory is better characterized as the ability to mentally form relations between elements, or to grasp relations in given information. This idea has been advanced, among others, by Graeme Halford, who illustrated it by our limited ability to understand statistical interactions between variables.{{cite journal | vauthors = Halford GS, Baker R, McCredden JE, Bain JD | title = How many variables can humans process? | journal = Psychological Science | volume = 16 | issue = 1 | pages = 70–76 | date = January 2005 | pmid = 15660854 | doi = 10.1111/j.0956-7976.2005.00782.x | s2cid = 9790149 }} These authors asked people to compare written statements about the relations between several variables to graphs illustrating the same or a different relation, as in the following sentence: "If the cake is from France, then it has more sugar if it is made with chocolate than if it is made with cream, but if the cake is from Italy, then it has more sugar if it is made with cream than if it is made of chocolate". This statement describes a relation between three variables (country, ingredient, and amount of sugar), which is the maximum most individuals can understand. The capacity limit apparent here is obviously not a memory limit (all relevant information can be seen continuously) but a limit to how many relationships are discerned simultaneously.{{citation needed|date=July 2022}}

There are several hypotheses about the nature of the capacity limit. One is that a limited pool of cognitive resources is needed to keep representations active and thereby available for processing, and for carrying out processes.{{cite journal | vauthors = Just MA, Carpenter PA | title = A capacity theory of comprehension: individual differences in working memory | journal = Psychological Review | volume = 99 | issue = 1 | pages = 122–149 | date = January 1992 | pmid = 1546114 | doi = 10.1037/0033-295X.99.1.122 | s2cid = 2241367 }} Another hypothesis is that memory traces in working memory decay within a few seconds, unless refreshed through rehearsal, and because the speed of rehearsal is limited, we can maintain only a limited amount of information.{{cite journal | vauthors = Towse JN, Hitch GJ, Hutton U | title = On the interpretation of working memory span in adults | journal = Memory & Cognition | volume = 28 | issue = 3 | pages = 341–348 | date = April 2000 | pmid = 10881551 | doi = 10.3758/BF03198549 | doi-access = free }} Yet another idea is that representations held in working memory interfere with each other.{{cite journal | vauthors = Waugh NC, Norman DA | title = PRIMARY MEMORY | journal = Psychological Review | volume = 72 | issue = 2 | pages = 89–104 | date = March 1965 | pmid = 14282677 | doi = 10.1037/h0021797 }}

The assumption that the contents of short-term or working memory decay over time, unless decay is prevented by rehearsal, goes back to the early days of experimental research on short-term memory.{{Cite journal| vauthors = Brown J |year=1958|title=Some tests of the decay theory of immediate memory|journal=Quarterly Journal of Experimental Psychology|volume=10|pages=12–21|doi=10.1080/17470215808416249|s2cid=144071312}}{{cite journal | vauthors = Peterson LR, Peterson MJ | title = Short-term retention of individual verbal items | journal = Journal of Experimental Psychology | volume = 58 | issue = 3 | pages = 193–198 | date = September 1959 | pmid = 14432252 | doi = 10.1037/h0049234 }} It is also an important assumption in the multi-component theory of working memory.{{Cite book|title=Working memory| vauthors = Baddeley AD |publisher=Clarendon | volume = 11 |year=1986|location=Oxford | isbn = 978-0-19-852116-7 }} The most elaborate decay-based theory of working memory to date is the "time-based resource sharing model".{{cite journal | vauthors = Barrouillet P, Bernardin S, Camos V | title = Time constraints and resource sharing in adults' working memory spans | journal = Journal of Experimental Psychology. General | volume = 133 | issue = 1 | pages = 83–100 | date = March 2004 | pmid = 14979753 | doi = 10.1037/0096-3445.133.1.83 | s2cid = 604840 }} This theory assumes that representations in working memory decay unless they are refreshed. Refreshing them requires an attentional mechanism that is also needed for any concurrent processing task. When there are small time intervals in which the processing task does not require attention, this time can be used to refresh memory traces. The theory therefore predicts that the amount of forgetting depends on the temporal density (rate and duration) of attentional demands of the processing task—this density is called cognitive load. The cognitive load depends on two variables, the rate at which the processing task requires individual steps to be carried out, and the duration of each step. For example, if the processing task consists of adding digits, then having to add another digit every half-second places a higher cognitive load on the system than having to add another digit every two seconds. In a series of experiments, Barrouillet and colleagues have shown that memory for lists of letters depends neither on the number of processing steps nor the total time of processing but on cognitive load.{{cite journal |last1=Barrouillet |first1=Pierre |last2=Bernardin |first2=Sophie |last3=Portrat |first3=Sophie |last4=Vergauwe |first4=Evie |last5=Camos |first5=Valérie |title=Time and cognitive load in working memory. |journal=Journal of Experimental Psychology: Learning, Memory, and Cognition |date=2007 |volume=33 |issue=3 |pages=570–585 |doi=10.1037/0278-7393.33.3.570 |pmid=17470006 |url=https://archive-ouverte.unige.ch/unige:88299 }}

Resource theories assume that the capacity of working memory is a limited resource that must be shared between all representations that need to be maintained in working memory simultaneously. Some resource theorists also assume that maintenance and concurrent processing share the same resource; this can explain why maintenance is typically impaired by a concurrent processing demand. Resource theories have been very successful in explaining data from tests of working memory for simple visual features, such as colors or orientations of bars. An ongoing debate is whether the resource is a continuous quantity that can be subdivided among any number of items in working memory, or whether it consists of a small number of discrete "slots", each of which can be assigned to one memory item, so that only a limited number of about 3 items can be maintained in working memory at all.{{cite journal | vauthors = van den Berg R, Awh E, Ma WJ | title = Factorial comparison of working memory models | journal = Psychological Review | volume = 121 | issue = 1 | pages = 124–149 | date = January 2014 | pmid = 24490791 | pmc = 4159389 | doi = 10.1037/a0035234 }}

Several forms of interference have been discussed by theorists. One of the oldest ideas is that new items simply replace older ones in working memory. Another form of interference is retrieval competition. For example, when the task is to remember a list of 7 words in their order, we need to start recall with the first word. While trying to retrieve the first word, the second word, which is represented in proximity, is accidentally retrieved as well, and the two compete for being recalled. Errors in serial recall tasks are often confusions of neighboring items on a memory list (so-called transpositions), showing that retrieval competition plays a role in limiting our ability to recall lists in order, and probably also in other working memory tasks. A third form of interference is the distortion of representations by superposition: When multiple representations are added on top of each other, each of them is blurred by the presence of all the others.{{cite journal |last1=Oberauer |first1=Klaus |last2=Lewandowsky |first2=Stephan |last3=Farrell |first3=Simon |last4=Jarrold |first4=Christopher |last5=Greaves |first5=Martin |title=Modeling working memory: An interference model of complex span |journal=Psychonomic Bulletin & Review |date=October 2012 |volume=19 |issue=5 |pages=779–819 |doi=10.3758/s13423-012-0272-4 |pmid=22715024 |url=https://www.zora.uzh.ch/id/eprint/63536/1/ZORA_NL_63536.pdf }} A fourth form of interference assumed by some authors is feature overwriting.{{Cite journal|doi=10.1016/j.jml.2006.08.009 |title=A formal model of capacity limits in working memory |date=November 2006 | vauthors = Oberauer K, Kliegl R |journal=Journal of Memory and Language |volume=55 |issue=4 |pages=601–26|doi-access=free }}{{cite journal | vauthors = Bancroft T, Servos P | title = Distractor frequency influences performance in vibrotactile working memory | journal = Experimental Brain Research | volume = 208 | issue = 4 | pages = 529–532 | date = February 2011 | pmid = 21132280 | doi = 10.1007/s00221-010-2501-2 | s2cid = 19743442 }} The idea is that each word, digit, or other item in working memory is represented as a bundle of features, and when two items share some features, one of them steals the features from the other. As more items are held in working memory, whose features begin to overlap, the more each of them will be degraded by the loss of some features.{{citation needed|date=July 2022}}

None of these hypotheses can explain the experimental data entirely. The resource hypothesis, for example, was meant to explain the trade-off between maintenance and processing: The more information must be maintained in working memory, the slower and more error prone concurrent processes become, and with a higher demand on concurrent processing memory suffers. This trade-off has been investigated by tasks like the reading-span task described above. It has been found that the amount of trade-off depends on the similarity of the information to be remembered and the information to be processed. For example, remembering numbers while processing spatial information, or remembering spatial information while processing numbers, impair each other much less than when material of the same kind must be remembered and processed.{{Cite journal|doi=10.1016/j.jml.2006.07.009 |title=The relationship between processing and storage in working memory span: Not two sides of the same coin |date=February 2007 | vauthors = Maehara Y, Saito S |journal=Journal of Memory and Language |volume=56 |issue=2 |pages=212–228}} Also, remembering words and processing digits, or remembering digits and processing words, is easier than remembering and processing materials of the same category.{{Cite journal|doi=10.1076/anec.6.2.99.784 |title=Selection from Working Memory: on the Relationship between Processing and Storage Components |date=June 1999 | vauthors = Li KZ |journal=Aging, Neuropsychology, and Cognition |volume=6 |issue=2 |pages=99–116}} These findings are also difficult to explain for the decay hypothesis, because decay of memory representations should depend only on how long the processing task delays rehearsal or recall, not on the content of the processing task. A further problem for the decay hypothesis comes from experiments in which the recall of a list of letters was delayed, either by instructing participants to recall at a slower pace, or by instructing them to say an irrelevant word once or three times in between recall of each letter. Delaying recall had virtually no effect on recall accuracy.{{cite journal |last1=Lewandowsky |first1=Stephan |last2=Duncan |first2=Matthew |last3=Brown |first3=Gordon D. A. |title=Time does not cause forgetting in short-term serial recall |journal=Psychonomic Bulletin & Review |date=October 2004 |volume=11 |issue=5 |pages=771–790 |doi=10.3758/bf03196705 |pmid=15732687 }}{{cite journal |last1=Oberauer |first1=Klaus |last2=Lewandowsky |first2=Stephan |title=Forgetting in immediate serial recall: Decay, temporal distinctiveness, or interference? |journal=Psychological Review |date=2008 |volume=115 |issue=3 |pages=544–576 |doi=10.1037/0033-295X.115.3.544 |pmid=18729591 |url=https://api.research-repository.uwa.edu.au/ws/files/1546099/11204_PID11204.pdf }} The interference theory seems to fare best with explaining why the similarity between memory contents and the contents of concurrent processing tasks affects how much they impair each other. More similar materials are more likely to be confused, leading to retrieval competition.

The capacity of working memory increases gradually over childhood{{cite journal | vauthors = Gathercole SE, Pickering SJ, Ambridge B, Wearing H | title = The structure of working memory from 4 to 15 years of age | journal = Developmental Psychology | volume = 40 | issue = 2 | pages = 177–190 | date = March 2004 | pmid = 14979759 | doi = 10.1037/0012-1649.40.2.177 }} and declines gradually in old age.{{cite journal | doi = 10.1037/0894-4105.8.4.535 | vauthors = Salthouse TA | year = 1994 | title = The aging of working memory | journal = Neuropsychology | volume = 8 | issue = 4| pages = 535–543 }}

{{Main|Neo-Piagetian theories of cognitive development}}

Measures of performance on tests of working memory increase continuously between early childhood and adolescence, while the structure of correlations between different tests remains largely constant. Starting with work in the Neo-Piagetian tradition,{{cite journal | doi = 10.1016/0001-6918(70)90108-3 | vauthors = Pascual-Leone J | year = 1970 | title = A mathematical model for the transition rule in Piaget's developmental stages | journal = Acta Psychologica | volume = 32 | pages = 301–345 }}{{cite book | vauthors = Case R | date = 1985 | title = Intellectual development. Birth to adulthood. | location = New York | publisher = Academic Press }} theorists have argued that the growth of working-memory capacity is a major driving force of cognitive development. This hypothesis has received substantial empirical support from studies showing that the capacity of working memory is a strong predictor of cognitive abilities in childhood.{{cite book | vauthors = Jarrold C, Bayliss DM | date = 2007 | chapter = Variation in working memory due to typical and atypical development. | veditors = Conway AR, Jarrold C, Kane MJ, Miyake A, Towse JN | title = Variation in working memory | pages = 137–161 | location = New York | publisher = Oxford University Press | isbn = 978-0-19-516864-8 | oclc = 1222332615 }} Particularly strong evidence for a role of working memory for development comes from a longitudinal study showing that working-memory capacity at one age predicts reasoning ability at a later age.{{cite journal | vauthors = Kail RV | title = Longitudinal evidence that increases in processing speed and working memory enhance children's reasoning | journal = Psychological Science | volume = 18 | issue = 4 | pages = 312–313 | date = April 2007 | pmid = 17470254 | doi = 10.1111/j.1467-9280.2007.01895.x | s2cid = 32240795 }} Studies in the Neo-Piagetian tradition have added to this picture by analyzing the complexity of cognitive tasks in terms of the number of items or relations that have to be considered simultaneously for a solution. Across a broad range of tasks, children manage task versions of the same level of complexity at about the same age, consistent with the view that working memory capacity limits the complexity they can handle at a given age.{{cite journal | vauthors = Andrews G, Halford GS | title = A cognitive complexity metric applied to cognitive development | journal = Cognitive Psychology | volume = 45 | issue = 2 | pages = 153–219 | date = September 2002 | pmid = 12528901 | doi = 10.1016/S0010-0285(02)00002-6 | s2cid = 30126328 }} One experiment has correlated that a decrease of complexity regarding capacity limits are articulated from research concerning language processes, outlining the effect on the capacity of children with language disorders, having performed lower than their age-matched peers. A correlation between memory storage deficits can be viewed as a contribution due to these language disorders, or rather the cause of the language disorder, but has not fully suggested a deficit in being able to rehearse information.{{cite journal | vauthors = Adams EJ, Nguyen AT, Cowan N | title = Theories of Working Memory: Differences in Definition, Degree of Modularity, Role of Attention, and Purpose | journal = Language, Speech, and Hearing Services in Schools | volume = 49 | issue = 3 | pages = 340–355 | date = July 2018 | pmid = 29978205 | pmc = 6105130 | doi = 10.1044/2018_LSHSS-17-0114 }}

Although neuroscience studies support the notion that children rely on prefrontal cortex for performing various working memory tasks, an fMRI meta-analysis on children compared to adults performing the n back task revealed a lack of consistent prefrontal cortex activation in children, while posterior regions including the insular cortex and cerebellum remain intact.{{cite journal | vauthors = Yaple Z, Arsalidou M | title = N-back Working Memory Task: Meta-analysis of Normative fMRI Studies With Children | journal = Child Development | volume = 89 | issue = 6 | pages = 2010–2022 | date = November 2018 | pmid = 29732553 | doi = 10.1111/cdev.13080 | url = }}

{{Original research section|reason=Refer to Talk:Working memory#Aging: pure original research to learn more.|date=April 2021}}

Working memory is among the cognitive functions most sensitive to decline in old age.{{cite journal | vauthors = Hertzog C, Dixon RA, Hultsch DF, MacDonald SW | title = Latent change models of adult cognition: are changes in processing speed and working memory associated with changes in episodic memory? | journal = Psychology and Aging | volume = 18 | issue = 4 | pages = 755–769 | date = December 2003 | pmid = 14692862 | doi = 10.1037/0882-7974.18.4.755 }}{{cite journal | vauthors = Park DC, Lautenschlager G, Hedden T, Davidson NS, Smith AD, Smith PK | title = Models of visuospatial and verbal memory across the adult life span | journal = Psychology and Aging | volume = 17 | issue = 2 | pages = 299–320 | date = June 2002 | pmid = 12061414 | doi = 10.1037/0882-7974.17.2.299 }} Several explanations for this decline have been offered. One is the processing speed theory of cognitive aging by Tim Salthouse.{{cite journal | vauthors = Salthouse TA | title = The processing-speed theory of adult age differences in cognition | journal = Psychological Review | volume = 103 | issue = 3 | pages = 403–428 | date = July 1996 | pmid = 8759042 | doi = 10.1037/0033-295X.103.3.403 }} Drawing on the finding that cognitive processes generally slow as people grow older, Salthouse argues that slower processing leaves more time for working memory content to decay, thus reducing effective capacity. However, the decline of working memory capacity cannot be entirely attributed to slowing because capacity declines more in old age than speed.{{cite journal | vauthors = Mayr U, Kliegl R, Krampe RT | title = Sequential and coordinative processing dynamics in figural transformations across the life span | journal = Cognition | volume = 59 | issue = 1 | pages = 61–90 | date = April 1996 | pmid = 8857471 | doi = 10.1016/0010-0277(95)00689-3 | s2cid = 25917331 }} Another proposal is the inhibition hypothesis advanced by Lynn Hasher and Rose Zacks.{{cite book | vauthors = Hasher L, Zacks RT | date = 1988 | chapter = Working memory, comprehension, and aging: A review and new view. | veditors = Bower GH | title = The psychology of learning and motivation | volume = 22 | pages = 193–225 | location = New York | publisher = Academic Press | isbn = 978-0-08-086373-3 | oclc = 476167241 }} This theory assumes a general deficit in old age in the ability to inhibit irrelevant information. Thus, working memory should tend to be cluttered with irrelevant content that reduces effective capacity for relevant content. The assumption of an inhibition deficit in old age has received much empirical support{{cite book | vauthors = Hasher L, Zacks RT, May CP | date = 1999 | chapter = Inhibitory control, circadian arousal, and age. | veditors = Gopher D, Koriat A | title = Attention and Performance | pages = 653–675 | location = Cambridge, MA | publisher = MIT Press | isbn = 978-0-262-31576-0 | oclc = 1120891520 }} but, so far, it is not clear whether the decline in inhibitory ability fully explains the decline of working memory capacity. An explanation on the neural level of the decline of working memory and other cognitive functions in old age has been proposed by West.{{cite journal | vauthors = West RL | title = An application of prefrontal cortex function theory to cognitive aging | journal = Psychological Bulletin | volume = 120 | issue = 2 | pages = 272–292 | date = September 1996 | pmid = 8831298 | doi = 10.1037/0033-2909.120.2.272 }} She argues that working memory depends to a large degree on the prefrontal cortex, which deteriorates more than other brain regions as we grow old. The prefrontal cortex hemodynamics also play an important role in the impairment of working memory through a prevalence of sleeping disorders that many older adults face but it is not the only region that is influenced since other brain regions have demonstrated an output of influence within neuroimaging studies.{{cite journal | vauthors = Gao J, Zhang L, Zhu J, Guo Z, Lin M, Bai L, Zheng P, Liu W, Huang J, Liu Z | display-authors = 6 | title = Prefrontal Cortex Hemodynamics and Functional Connectivity Changes during Performance Working Memory Tasks in Older Adults with Sleep Disorders | journal = Brain Sciences | volume = 13 | issue = 3 | pages = 497 | date = March 2023 | pmid = 36979307 | pmc = 10046575 | doi = 10.3390/brainsci13030497 | doi-access = free }}{{cite journal | vauthors = Wu G, Wang Y, Mwansisya TE, Pu W, Zhang H, Liu C, Yang Q, Chen EY, Xue Z, Liu Z, Shan B | display-authors = 6 | title = Effective connectivity of the posterior cingulate and medial prefrontal cortices relates to working memory impairment in schizophrenic and bipolar patients | journal = Schizophrenia Research | volume = 158 | issue = 1–3 | pages = 85–90 | date = September 2014 | pmid = 25043264 | doi = 10.1016/j.schres.2014.06.033 | s2cid = 36643966 }} Within the studies of fMRI, a connection between sleep deprivation was observed through a reduction of performance on the prefrontal cortex and a overall decrease in working memory performance.{{cite journal | vauthors = Guo Z, Jiang Z, Jiang B, McClure MA, Mu Q | title = High-Frequency Repetitive Transcranial Magnetic Stimulation Could Improve Impaired Working Memory Induced by Sleep Deprivation | journal = Neural Plasticity | volume = 2019 | pages = 7030286 | date = 2019-12-12 | pmid = 31915432 | pmc = 6930796 | doi = 10.1155/2019/7030286 | doi-access = free }} Age-related decline in working memory can be briefly reversed using low intensity transcranial stimulation to synchronize rhythms in prefrontal and temporal areas.{{Cite news |url= https://www.theguardian.com/science/2019/apr/08/scientists-use-electrical-pulses-reverse-memory-decline-ageing|title=Scientists reverse memory decline using electrical pulses| vauthors = Devlin H |date=2019-04-08|work=The Guardian|access-date=2019-04-09|language=en-GB|issn=0261-3077}}

The neurobiological bases for reduced working memory abilities has been studied in aging macaques, who naturally develop impairments in working memory and the executive functions.{{cite journal |last1=Morrison |first1=John H. |last2=Baxter |first2=Mark G. |title=The ageing cortical synapse: hallmarks and implications for cognitive decline |journal=Nature Reviews Neuroscience |date=April 2012 |volume=13 |issue=4 |pages=240–250 |doi=10.1038/nrn3200 |pmid=22395804 |pmc=3592200 }} Research has shown that aged macaques have reduced working memory-related neuronal firing in the dorsolateral prefrontal cortex, that arises in part from excessive cAMP-PKA-calcium signaling, which opens nearby potassium channels that weaken the glutamate synapses on spines needed to maintain persistent firing across the delay period when there is no sensory stimulation.{{cite journal |last1=Wang |first1=Min |last2=Gamo |first2=Nao J. |last3=Yang |first3=Yang |last4=Jin |first4=Lu E. |last5=Wang |first5=Xiao-Jing |last6=Laubach |first6=Mark |last7=Mazer |first7=James A. |last8=Lee |first8=Daeyeol |last9=Arnsten |first9=Amy F. T. |title=Neuronal basis of age-related working memory decline |journal=Nature |date=August 2011 |volume=476 |issue=7359 |pages=210–213 |doi=10.1038/nature10243 |pmid=21796118 |pmc=3193794 |bibcode=2011Natur.476..210W }} Dysregulation of this process with age likely involves increased inflammation with age.{{cite journal |last1=Arnsten |first1=Amy F. T. |last2=Datta |first2=Dibyadeep |last3=Wang |first3=Min |title=The genie in the bottle-magnified calcium signaling in dorsolateral prefrontal cortex |journal=Molecular Psychiatry |date=August 2021 |volume=26 |issue=8 |pages=3684–3700 |doi=10.1038/s41380-020-00973-3 |pmid=33319854 |pmc=8203737 }} Sustained weakness leads to loss of dendritic spines, the site of essential glutamate connections.{{cite journal |last1=Morrison |first1=John H. |last2=Baxter |first2=Mark G. |title=The ageing cortical synapse: hallmarks and implications for cognitive decline |journal=Nature Reviews Neuroscience |date=April 2012 |volume=13 |issue=4 |pages=240–250 |doi=10.1038/nrn3200 |pmid=22395804 |pmc=3592200 }}

{{Further|Working memory training|Neurobiological effects of physical exercise#Cognitive control and memory}}

Some studies in the effects of training on working memory, including the first by Torkel Klingberg, suggest that working memory in those with ADHD can improve by training.{{cite journal | vauthors = Klingberg T, Forssberg H, Westerberg H | title = Training of working memory in children with ADHD | journal = Journal of Clinical and Experimental Neuropsychology | volume = 24 | issue = 6 | pages = 781–791 | date = September 2002 | pmid = 12424652 | doi = 10.1076/jcen.24.6.781.8395 | s2cid = 146570079 }} This study found that a period of working memory training increases a range of cognitive abilities and increases IQ test scores. Another study by the same group{{cite journal | vauthors = Olesen PJ, Westerberg H, Klingberg T | title = Increased prefrontal and parietal activity after training of working memory | journal = Nature Neuroscience | volume = 7 | issue = 1 | pages = 75–79 | date = January 2004 | pmid = 14699419 | doi = 10.1038/nn1165 | s2cid = 6362120 }} has shown that, after training, measured brain activity related to working memory increased in the prefrontal cortex, an area that many researchers have associated with working memory functions. One study has shown that working memory training increases the density of prefrontal and parietal dopamine receptors (specifically, DRD1) in test subjects.{{cite journal | vauthors = McNab F, Varrone A, Farde L, Jucaite A, Bystritsky P, Forssberg H, Klingberg T | title = Changes in cortical dopamine D1 receptor binding associated with cognitive training | journal = Science | volume = 323 | issue = 5915 | pages = 800–802 | date = February 2009 | pmid = 19197069 | doi = 10.1126/science.1166102 | bibcode = 2009Sci...323..800M | s2cid = 206516408 }} However, subsequent experiments with the same training program have shown mixed results, with some successfully replicating, and others failing to replicate the beneficial effects of training on cognitive performance.{{cite journal | vauthors = Katz B, Shah P, Meyer DE | title = How to play 20 questions with nature and lose: Reflections on 100 years of brain-training research | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 115 | issue = 40 | pages = 9897–9904 | date = October 2018 | pmid = 30275315 | pmc = 6176639 | doi = 10.1073/pnas.1617102114 | doi-access = free | bibcode = 2018PNAS..115.9897K }}

In another influential study, training with a working memory task (the dual n-back task) improved performance on a fluid intelligence test in healthy young adults.{{cite journal | vauthors = Jaeggi SM, Buschkuehl M, Jonides J, Perrig WJ | title = Improving fluid intelligence with training on working memory | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 105 | issue = 19 | pages = 6829–6833 | date = May 2008 | pmid = 18443283 | pmc = 2383929 | doi = 10.1073/pnas.0801268105 | doi-access = free | bibcode = 2008PNAS..105.6829J }} The improvement of fluid intelligence by training with the n-back task was replicated in 2010,{{cite journal| vauthors = Jaeggi SM, Studer-Luethi B, Buschkuehl M, Su YF, Jonides J, Perrig WJ |title=The relationship between n-back performance and matrix reasoning – implications for training and transfer|journal=Intelligence|volume=38|issue=6|year=2010|pages=625–635|issn=0160-2896|doi=10.1016/j.intell.2010.09.001}} but two studies published in 2012 failed to reproduce the effect.{{cite journal | vauthors = Redick TS, Shipstead Z, Harrison TL, Hicks KL, Fried DE, Hambrick DZ, Kane MJ, Engle RW | display-authors = 6 | title = No evidence of intelligence improvement after working memory training: a randomized, placebo-controlled study | journal = Journal of Experimental Psychology. General | volume = 142 | issue = 2 | pages = 359–379 | date = May 2013 | pmid = 22708717 | doi = 10.1037/a0029082 | s2cid = 15117431 }}{{cite journal| vauthors = Chooi WT, Thompson LA | title=Working memory training does not improve intelligence in healthy young adults| journal=Intelligence| volume=40|issue=6| year=2012| pages=531–542| issn=0160-2896| doi=10.1016/j.intell.2012.07.004}} The combined evidence from about 30 experimental studies on the effectiveness of working-memory training has been evaluated by several meta-analyses.{{cite journal |last1=Au |first1=Jacky |last2=Sheehan |first2=Ellen |last3=Tsai |first3=Nancy |last4=Duncan |first4=Greg J. |last5=Buschkuehl |first5=Martin |last6=Jaeggi |first6=Susanne M. |title=Improving fluid intelligence with training on working memory: a meta-analysis |journal=Psychonomic Bulletin & Review |date=April 2015 |volume=22 |issue=2 |pages=366–377 |doi=10.3758/s13423-014-0699-x |pmid=25102926 |url=https://escholarship.org/uc/item/1mj701dj }}{{cite journal | vauthors = Melby-Lervåg M, Redick TS, Hulme C | title = Working Memory Training Does Not Improve Performance on Measures of Intelligence or Other Measures of "Far Transfer": Evidence From a Meta-Analytic Review | journal = Perspectives on Psychological Science | volume = 11 | issue = 4 | pages = 512–534 | date = July 2016 | pmid = 27474138 | pmc = 4968033 | doi = 10.1177/1745691616635612 }} The authors of these meta-analyses disagree in their conclusions as to whether or not working-memory training improves intelligence. Yet these meta-analyses agree that, the more distant the outcome measure, the weaker is the causal link – training working memory almost always yields increases in working memory, often in attention, and sometimes in academic performance, but it is still an outstanding question what exact circumstances differs between cases of successful and unsuccessful transfer of effects.{{Cite report | vauthors = Berger EM, Fehr E, Hermes H, Schunk D, Winkel K |date=2020 |title=The Impact of Working Memory Training on Children's Cognitive and Noncognitive Skills |doi=10.2139/ssrn.3622985|s2cid=221652470 |hdl=10419/222352 |hdl-access=free }}

The first insights into the neuronal and neurotransmitter basis of working memory came from animal research. The work of Jacobsen{{Cite journal| vauthors = Jacobsen CF |title= Studies of cerebral function in primates |journal=Comparative Psychology Monographs |volume=13 |issue=3 |pages=1–68 |year=1938 |oclc=250695441 }} and Fulton in the 1930s first showed that lesions to the PFC impaired spatial working memory performance in monkeys. The later work of Joaquin Fuster{{cite journal | vauthors = Fuster JM | title = Unit activity in prefrontal cortex during delayed-response performance: neuronal correlates of transient memory | journal = Journal of Neurophysiology | volume = 36 | issue = 1 | pages = 61–78 | date = January 1973 | pmid = 4196203 | doi = 10.1152/jn.1973.36.1.61 | s2cid = 17534879 | doi-access = free }} recorded the electrical activity of neurons in the PFC of monkeys while they were doing a delayed matching task. In that task, the monkey sees how the experimenter places a bit of food under one of two identical-looking cups. A shutter is then lowered for a variable delay period, screening off the cups from the monkey's view. After the delay, the shutter opens and the monkey is allowed to retrieve the food from under the cups. Successful retrieval in the first attempt – something the animal can achieve after some training on the task – requires holding the location of the food in memory over the delay period. Fuster found neurons in the PFC that fired mostly during the delay period, suggesting that they were involved in representing the food location while it was invisible. Later research has shown similar delay-active neurons also in the posterior parietal cortex, the thalamus, the caudate, and the globus pallidus.{{cite journal | vauthors = Ashby FG, Ell SW, Valentin VV, Casale MB | title = FROST: a distributed neurocomputational model of working memory maintenance | journal = Journal of Cognitive Neuroscience | volume = 17 | issue = 11 | pages = 1728–1743 | date = November 2005 | pmid = 16269109 | doi = 10.1162/089892905774589271 | s2cid = 12765957 }} The work of Goldman-Rakic and others showed that principal sulcal, dorsolateral PFC interconnects with all of these brain regions, and that neuronal microcircuits within PFC are able to maintain information in working memory through recurrent excitatory glutamate networks of pyramidal cells that continue to fire throughout the delay period.{{cite journal | vauthors = Goldman-Rakic PS | title = Cellular basis of working memory | journal = Neuron | volume = 14 | issue = 3 | pages = 477–485 | date = March 1995 | pmid = 7695894 | doi = 10.1016/0896-6273(95)90304-6 | s2cid = 2972281 | doi-access = free }} These circuits are tuned by lateral inhibition from GABAergic interneurons.{{cite journal | vauthors = Rao SG, Williams GV, Goldman-Rakic PS | title = Destruction and creation of spatial tuning by disinhibition: GABA(A) blockade of prefrontal cortical neurons engaged by working memory | journal = The Journal of Neuroscience | volume = 20 | issue = 1 | pages = 485–494 | date = January 2000 | pmid = 10627624 | pmc = 6774140 | doi = 10.1523/JNEUROSCI.20-01-00485.2000 }} The neuromodulatory arousal systems markedly alter PFC working memory function; for example, either too little or too much dopamine or norepinephrine impairs PFC network firing{{cite journal | vauthors = Arnsten AF, Paspalas CD, Gamo NJ, Yang Y, Wang M | title = Dynamic Network Connectivity: A new form of neuroplasticity | journal = Trends in Cognitive Sciences | volume = 14 | issue = 8 | pages = 365–375 | date = August 2010 | pmid = 20554470 | pmc = 2914830 | doi = 10.1016/j.tics.2010.05.003 }} and working memory performance.{{cite journal | vauthors = Robbins TW, Arnsten AF | title = The neuropsychopharmacology of fronto-executive function: monoaminergic modulation | journal = Annual Review of Neuroscience | volume = 32 | pages = 267–287 | year = 2009 | pmid = 19555290 | pmc = 2863127 | doi = 10.1146/annurev.neuro.051508.135535 }} A brain network analysis demonstrates that the FPC network requires less induced energy during working memory tasks than other functional brain networks. This finding underscores the efficient processing of the FPC network and highlights its crucial role in supporting working memory processes.{{cite journal | vauthors = Saberi M, Rieck JR, Golafshan S, Grady CL, Misic B, Dunkley BT, Khatibi A | title = The brain selectively allocates energy to functional brain networks under cognitive control | journal = Scientific Reports | date = 2024 | volume = 14 | issue = 1 | pages = 32032 | doi = 10.1038/s41598-024-83696-7 | pmid = 39738735 | url = https://doi.org/10.1038/s41598-024-83696-7 | pmc = 11686059 | bibcode = 2024NatSR..1432032S }}

The research described above on persistent firing of certain neurons in the delay period of working memory tasks shows that the brain has a mechanism of keeping representations active without external input. Keeping representations active, however, is not enough if the task demands maintaining more than one chunk of information. In addition, the components and features of each chunk must be bound together to prevent them from being mixed up. For example, if a red triangle and a green square must be remembered at the same time, one must make sure that "red" is bound to "triangle" and "green" is bound to "square". One way of establishing such bindings is by having the neurons that represent features of the same chunk fire in synchrony, and those that represent features belonging to different chunks fire out of sync.{{cite journal | vauthors = Raffone A, Wolters G | title = A cortical mechanism for binding in visual working memory | journal = Journal of Cognitive Neuroscience | volume = 13 | issue = 6 | pages = 766–785 | date = August 2001 | pmid = 11564321 | doi = 10.1162/08989290152541430 | s2cid = 23241633 }} In the example, neurons representing redness would fire in synchrony with neurons representing the triangular shape, but out of sync with those representing the square shape. So far, there is no direct evidence that working memory uses this binding mechanism, and other mechanisms have been proposed as well.{{cite book |doi=10.1093/acprof:oso/9780198508571.003.0009 |chapter=Three forms of binding and their neural substrates: Alternatives to temporal synchrony |title=The Unity of ConsciousnessBinding, Integration, and Dissociation |date=2003 |last1=Oʼreilly |first1=Randall C. |last2=Busby |first2=Richard S. |last3=Soto |first3=Rodolfo |pages=168–190 |isbn=978-0-19-850857-1 }} It has been speculated that synchronous firing of neurons involved in working memory oscillate with frequencies in the theta band (4 to 8 Hz). Indeed, the power of theta frequency in the EEG increases with working memory load,{{Cite book|title=Handbook of binding and memory|publisher=Oxford University Press|year=2006|location=Oxford|pages=115–144|chapter=Binding principles in the theta frequency range| vauthors = Klimesch W | veditors = Zimmer HD, Mecklinger A, Lindenberger U }} and oscillations in the theta band measured over different parts of the skull become more coordinated when the person tries to remember the binding between two components of information.{{cite journal | vauthors = Wu X, Chen X, Li Z, Han S, Zhang D | title = Binding of verbal and spatial information in human working memory involves large-scale neural synchronization at theta frequency | journal = NeuroImage | volume = 35 | issue = 4 | pages = 1654–1662 | date = May 2007 | pmid = 17379539 | doi = 10.1016/j.neuroimage.2007.02.011 | s2cid = 7676564 }}

Localization of brain functions in humans has become much easier with the advent of brain imaging methods (PET and fMRI). This research has confirmed that areas in the PFC are involved in working memory functions. During the 1990s much debate had centered on the different functions of the ventrolateral (i.e., lower areas) and the dorsolateral (higher) areas of the PFC. A human lesion study provides additional evidence for the role of the dorsolateral prefrontal cortex in working memory.{{cite journal | vauthors = Barbey AK, Koenigs M, Grafman J | title = Dorsolateral prefrontal contributions to human working memory | journal = Cortex; A Journal Devoted to the Study of the Nervous System and Behavior | volume = 49 | issue = 5 | pages = 1195–1205 | date = May 2013 | pmid = 22789779 | pmc = 3495093 | doi = 10.1016/j.cortex.2012.05.022 }} One view was that the dorsolateral areas are responsible for spatial working memory and the ventrolateral areas for non-spatial working memory. Another view proposed a functional distinction, arguing that ventrolateral areas are mostly involved in pure maintenance of information, whereas dorsolateral areas are more involved in tasks requiring some processing of the memorized material. The debate is not entirely resolved but most of the evidence supports the functional distinction.{{cite journal | vauthors = Owen AM | title = The functional organization of working memory processes within human lateral frontal cortex: the contribution of functional neuroimaging | journal = The European Journal of Neuroscience | volume = 9 | issue = 7 | pages = 1329–1339 | date = July 1997 | pmid = 9240390 | doi = 10.1111/j.1460-9568.1997.tb01487.x | s2cid = 2119538 }}

Brain imaging has revealed that working memory functions are not limited to the PFC. A review of numerous studies{{cite journal | vauthors = Smith EE, Jonides J | title = Storage and executive processes in the frontal lobes | journal = Science | volume = 283 | issue = 5408 | pages = 1657–1661 | date = March 1999 | pmid = 10073923 | doi = 10.1126/science.283.5408.1657 | bibcode = 1999Sci...283.1657. }} shows areas of activation during working memory tasks scattered over a large part of the cortex. There is a tendency for spatial tasks to recruit more right-hemisphere areas, and for verbal and object working memory to recruit more left-hemisphere areas. The activation during verbal working memory tasks can be broken down into one component reflecting maintenance, in the left posterior parietal cortex, and a component reflecting subvocal rehearsal, in the left frontal cortex (Broca's area, known to be involved in speech production).{{cite journal | vauthors = Smith EE, Jonides J, Marshuetz C, Koeppe RA | title = Components of verbal working memory: evidence from neuroimaging | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 95 | issue = 3 | pages = 876–882 | date = February 1998 | pmid = 9448254 | pmc = 33811 | doi = 10.1073/pnas.95.3.876 | doi-access = free | bibcode = 1998PNAS...95..876S }}

There is an emerging consensus that most working memory tasks recruit a network of PFC and parietal areas. A study has shown that during a working memory task the connectivity between these areas increases.{{cite journal | vauthors = Honey GD, Fu CH, Kim J, Brammer MJ, Croudace TJ, Suckling J, Pich EM, Williams SC, Bullmore ET | display-authors = 6 | title = Effects of verbal working memory load on corticocortical connectivity modeled by path analysis of functional magnetic resonance imaging data | journal = NeuroImage | volume = 17 | issue = 2 | pages = 573–582 | date = October 2002 | pmid = 12377135 | doi = 10.1016/S1053-8119(02)91193-6 }} Another study has demonstrated that these areas are necessary for working memory, and not simply activated accidentally during working memory tasks, by temporarily blocking them through transcranial magnetic stimulation (TMS), thereby producing an impairment in task performance.{{cite journal | vauthors = Mottaghy FM | title = Interfering with working memory in humans | journal = Neuroscience | volume = 139 | issue = 1 | pages = 85–90 | date = April 2006 | pmid = 16337091 | doi = 10.1016/j.neuroscience.2005.05.037 | s2cid = 20079590 }}

A current debate concerns the function of these brain areas. The PFC has been found to be active in a variety of tasks that require executive functions. This has led some researchers to argue that the role of PFC in working memory is in controlling attention, selecting strategies, and manipulating information in working memory, but not in maintenance of information. The maintenance function is attributed to more posterior areas of the brain, including the parietal cortex.{{cite journal | vauthors = Curtis CE, D'Esposito M | title = Persistent activity in the prefrontal cortex during working memory | journal = Trends in Cognitive Sciences | volume = 7 | issue = 9 | pages = 415–423 | date = September 2003 | pmid = 12963473 | doi = 10.1016/S1364-6613(03)00197-9 | s2cid = 15763406 }}{{cite journal | vauthors = Postle BR | title = Working memory as an emergent property of the mind and brain | journal = Neuroscience | volume = 139 | issue = 1 | pages = 23–38 | date = April 2006 | pmid = 16324795 | pmc = 1428794 | doi = 10.1016/j.neuroscience.2005.06.005 }} Other authors interpret the activity in parietal cortex as reflecting executive functions, because the same area is also activated in other tasks requiring attention but not memory.{{cite journal | vauthors = Collette F, Hogge M, Salmon E, Van der Linden M | title = Exploration of the neural substrates of executive functioning by functional neuroimaging | journal = Neuroscience | volume = 139 | issue = 1 | pages = 209–221 | date = April 2006 | pmid = 16324796 | doi = 10.1016/j.neuroscience.2005.05.035 | hdl-access = free | s2cid = 15473485 | hdl = 2268/5937 }} Evidence from decoding studying employing multi-voxel-pattern-analysis of fMRI data showed the content of visual working memory can be decoded from activity patterns in visual cortex, but not prefrontal cortex.{{cite journal | vauthors = Sreenivasan KK, Curtis CE, D'Esposito M | title = Revisiting the role of persistent neural activity during working memory | journal = Trends in Cognitive Sciences | volume = 18 | issue = 2 | pages = 82–89 | date = February 2014 | pmid = 24439529 | pmc = 3964018 | doi = 10.1016/j.tics.2013.12.001 }} This led to the suggestion that the maintenance function of visual working memory is performed by visual cortex while the role of the prefrontal cortex is in executive control over working memory though it has been pointed out that such comparisons do not take into account the base rate of decoding across different regions.{{cite journal | vauthors = Bhandari A, Gagne C, Badre D | title = Just above Chance: Is It Harder to Decode Information from Prefrontal Cortex Hemodynamic Activity Patterns? | journal = Journal of Cognitive Neuroscience | volume = 30 | issue = 10 | pages = 1473–1498 | date = October 2018 | pmid = 29877764 | doi = 10.1162/jocn_a_01291 | s2cid = 46954312 }}

A 2003 meta-analysis of 60 neuroimaging studies found left frontal cortex was involved in low-task demand verbal working memory and right frontal cortex for spatial working memory. Brodmann's areas (BAs) 6, 8, and 9, in the superior frontal cortex was involved when working memory must be continuously updated and when memory for temporal order had to be maintained. Right Brodmann 10 and 47 in the ventral frontal cortex were involved more frequently with demand for manipulation such as dual-task requirements or mental operations, and Brodmann 7 in the posterior parietal cortex was also involved in all types of executive function.{{cite journal | vauthors = Wager TD, Smith EE | title = Neuroimaging studies of working memory: a meta-analysis | journal = Cognitive, Affective & Behavioral Neuroscience | volume = 3 | issue = 4 | pages = 255–274 | date = December 2003 | pmid = 15040547 | doi = 10.3758/cabn.3.4.255 | doi-access = free }} Updating information in visual working memory is also influenced by the functional neural network connecting different brain regions.{{Cite journal |last=Velichkovsky |first=B. B. |last2=Kozlovskiy |first2=S. A. |last3=Buldakova |first3=N. S. |last4=Ushakov |first4=V. L. |last5=Kartashov |first5=S. I. |last6=Vartanov |first6=A. V. |date=2018-10-01 |title=The neurocognitive mechanisms of working memory updating |url=https://linkinghub.elsevier.com/retrieve/pii/S0167876018307931 |journal=International Journal of Psychophysiology |series= |volume=131 |pages=S171–S172 |doi=10.1016/j.ijpsycho.2018.07.452 |issn=0167-8760|url-access=subscription }} The dorsolateral PFC plays a crucial role in this process. In particular, the middle frontal gyrus may be involved in the maintenance, and the frontal operculum in the controlled processing of materials in working memory. Studies have also shown the role of attentional switching in working memory updating, mediated by the superior parietal lobule. Working memory updating also involves a repetition mechanism mediated by the temporal cortex. And in addition, the process of working memory updating involves the sensory cortex to encode and store certain visual stimuli, such as geometric shapes (inferior occipital gyrus) and faces (fusiform gyrus).

Working memory has been suggested to involve two processes with different neuroanatomical locations in the frontal and parietal lobes.{{cite journal | vauthors = Bledowski C, Rahm B, Rowe JB | title = What 'works' in working memory? Separate systems for selection and updating of critical information | journal = The Journal of Neuroscience | volume = 29 | issue = 43 | pages = 13735–13741 | date = October 2009 | pmid = 19864586 | pmc = 2785708 | doi = 10.1523/JNEUROSCI.2547-09.2009 }} First, a selection operation that retrieves the most relevant item, and second an updating operation that changes the focus of attention made upon it. Updating the attentional focus has been found to involve the transient activation in the caudal superior frontal sulcus and posterior parietal cortex, while increasing demands on selection selectively changes activation in the rostral superior frontal sulcus and posterior cingulate/precuneus.

Articulating the differential function of brain regions involved in working memory is dependent on tasks able to distinguish these functions.{{cite journal | vauthors = Coltheart M | title = What has functional neuroimaging told us about the mind (so far)? | journal = Cortex; A Journal Devoted to the Study of the Nervous System and Behavior | volume = 42 | issue = 3 | pages = 323–331 | date = April 2006 | pmid = 16771037 | doi = 10.1016/S0010-9452(08)70358-7 | s2cid = 4485292 }} Most brain imaging studies of working memory have used recognition tasks such as delayed recognition of one or several stimuli, or the n-back task, in which each new stimulus in a long series must be compared to the one presented n steps back in the series. The advantage of recognition tasks is that they require minimal movement (just pressing one of two keys), making fixation of the head in the scanner easier. Experimental research and research on individual differences in working memory, however, has used largely recall tasks (e.g., the reading span task, see below). It is not clear to what degree recognition and recall tasks reflect the same processes and the same capacity limitations.

Brain imaging studies have been conducted with the reading span task or related tasks. Increased activation during these tasks was found in the PFC and, in several studies, also in the anterior cingulate cortex (ACC). People performing better on the task showed larger increase of activation in these areas, and their activation was correlated more over time, suggesting that their neural activity in these two areas was better coordinated, possibly due to stronger connectivity.{{cite journal | vauthors = Kondo H, Osaka N, Osaka M | title = Cooperation of the anterior cingulate cortex and dorsolateral prefrontal cortex for attention shifting | journal = NeuroImage | volume = 23 | issue = 2 | pages = 670–679 | date = October 2004 | pmid = 15488417 | doi = 10.1016/j.neuroimage.2004.06.014 | s2cid = 16979638 }}{{cite journal | vauthors = Osaka N, Osaka M, Kondo H, Morishita M, Fukuyama H, Shibasaki H | title = The neural basis of executive function in working memory: an fMRI study based on individual differences | journal = NeuroImage | volume = 21 | issue = 2 | pages = 623–631 | date = February 2004 | pmid = 14980565 | doi = 10.1016/j.neuroimage.2003.09.069 | s2cid = 7195491 }}

One approach to modeling the neurophysiology and the functioning of working memory is prefrontal cortex basal ganglia working memory (PBWM). In this model, the prefrontal cortex works hand-in-hand with the basal ganglia to accomplish the tasks of working memory. Many studies have shown this to be the case.{{cite journal | vauthors = Baier B, Karnath HO, Dieterich M, Birklein F, Heinze C, Müller NG | title = Keeping memory clear and stable—the contribution of human basal ganglia and prefrontal cortex to working memory | journal = The Journal of Neuroscience | volume = 30 | issue = 29 | pages = 9788–9792 | date = July 2010 | pmid = 20660261 | pmc = 6632833 | doi = 10.1523/jneurosci.1513-10.2010 | doi-access = free }} One used ablation techniques in patients who had had seizures and had damage to the prefrontal cortex and basal ganglia. Researchers found that such damage resulted in decreased capacity to carry out the executive function of working memory.{{cite journal | vauthors = Voytek B, Knight RT | title = Prefrontal cortex and basal ganglia contributions to visual working memory | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 107 | issue = 42 | pages = 18167–18172 | date = October 2010 | pmid = 20921401 | pmc = 2964236 | doi = 10.1073/pnas.1007277107 | doi-access = free | bibcode = 2010PNAS..10718167V }} Additional research conducted on patients with brain alterations due to methamphetamine use found that training working memory increases volume in the basal ganglia.{{cite journal | vauthors = Brooks SJ, Burch KH, Maiorana SA, Cocolas E, Schioth HB, Nilsson EK, Kamaloodien K, Stein DJ | display-authors = 6 | title = Psychological intervention with working memory training increases basal ganglia volume: A VBM study of inpatient treatment for methamphetamine use | journal = NeuroImage. Clinical | volume = 12 | pages = 478–491 | date = 2016-02-01 | pmid = 27625988 | pmc = 5011179 | doi = 10.1016/j.nicl.2016.08.019 | doi-access = free }}

Working memory is impaired by acute and chronic psychological stress. This phenomenon was first discovered in animal studies by Arnsten and colleagues,{{cite journal | vauthors = Arnsten AF | title = The biology of being frazzled | journal = Science | volume = 280 | issue = 5370 | pages = 1711–1712 | date = June 1998 | pmid = 9660710 | doi = 10.1126/science.280.5370.1711 | s2cid = 25842149 }} who have shown that stress-induced catecholamine release in PFC rapidly decreases PFC neuronal firing and impairs working memory performance through feedforward, intracellular signaling pathways that open potassium channels to rapidly weaken prefrontal network connections.{{cite journal | vauthors = Arnsten AF | title = Stress signalling pathways that impair prefrontal cortex structure and function | journal = Nature Reviews. Neuroscience | volume = 10 | issue = 6 | pages = 410–422 | date = June 2009 | pmid = 19455173 | pmc = 2907136 | doi = 10.1038/nrn2648 }} This process of rapid changes in network strength is called Dynamic Network Connectivity,{{cite journal |last1=Arnsten |first1=Amy F.T. |last2=Paspalas |first2=Constantinos D. |last3=Gamo |first3=Nao J. |last4=Yang |first4=Yang |last5=Wang |first5=Min |title=Dynamic Network Connectivity: A new form of neuroplasticity |journal=Trends in Cognitive Sciences |date=August 2010 |volume=14 |issue=8 |pages=365–375 |doi=10.1016/j.tics.2010.05.003 |pmid=20554470 |pmc=2914830 }} and can be seen in human brain imaging when cortical functional connectivity rapidly changes in response to a stressor.{{cite journal |last1=Hermans |first1=Erno J. |last2=van Marle |first2=Hein J. F. |last3=Ossewaarde |first3=Lindsey |last4=Henckens |first4=Marloes J. A. G. |last5=Qin |first5=Shaozheng |last6=van Kesteren |first6=Marlieke T. R. |last7=Schoots |first7=Vincent C. |last8=Cousijn |first8=Helena |last9=Rijpkema |first9=Mark |last10=Oostenveld |first10=Robert |last11=Fernández |first11=Guillén |title=Stress-Related Noradrenergic Activity Prompts Large-Scale Neural Network Reconfiguration |journal=Science |date=25 November 2011 |volume=334 |issue=6059 |pages=1151–1153 |doi=10.1126/science.1209603 |pmid=22116887 |bibcode=2011Sci...334.1151H }} Exposure to chronic stress leads to more profound working memory deficits and additional architectural changes in PFC, including dendritic atrophy and spine loss,{{cite journal | vauthors = Radley JJ, Rocher AB, Miller M, Janssen WG, Liston C, Hof PR, McEwen BS, Morrison JH | display-authors = 6 | title = Repeated stress induces dendritic spine loss in the rat medial prefrontal cortex | journal = Cerebral Cortex | volume = 16 | issue = 3 | pages = 313–320 | date = March 2006 | pmid = 15901656 | doi = 10.1093/cercor/bhi104 | doi-access = free }} which can be prevented by inhibition of protein kinase C signaling.{{cite journal | vauthors = Hains AB, Vu MA, Maciejewski PK, van Dyck CH, Gottron M, Arnsten AF | title = Inhibition of protein kinase C signaling protects prefrontal cortex dendritic spines and cognition from the effects of chronic stress | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 106 | issue = 42 | pages = 17957–17962 | date = October 2009 | pmid = 19805148 | pmc = 2742406 | doi = 10.1073/pnas.0908563106 | doi-access = free | bibcode = 2009PNAS..10617957H | author-link4 = Christopher H. van Dyck }} fMRI research has extended this research to humans, and confirms that reduced working memory caused by acute stress links to reduced activation of the PFC, and stress increased levels of catecholamines.{{cite journal | vauthors = Qin S, Hermans EJ, van Marle HJ, Luo J, Fernández G | title = Acute psychological stress reduces working memory-related activity in the dorsolateral prefrontal cortex | journal = Biological Psychiatry | volume = 66 | issue = 1 | pages = 25–32 | date = July 2009 | pmid = 19403118 | doi = 10.1016/j.biopsych.2009.03.006 | s2cid = 22601360 }} Imaging studies of medical students undergoing stressful exams have also shown weakened PFC functional connectivity, consistent with the animal studies.{{cite journal | vauthors = Liston C, McEwen BS, Casey BJ | title = Psychosocial stress reversibly disrupts prefrontal processing and attentional control | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 106 | issue = 3 | pages = 912–917 | date = January 2009 | pmid = 19139412 | pmc = 2621252 | doi = 10.1073/pnas.0807041106 | doi-access = free | bibcode = 2009PNAS..106..912L }} The marked effects of stress on PFC structure and function may help to explain how stress can cause or exacerbate mental illness.

The more stress in one's life, the lower the efficiency of working memory in performing simple cognitive tasks. Students who performed exercises that reduced the intrusion of negative thoughts showed an increase in their working memory capacity. Mood states (positive or negative) can have an influence on the neurotransmitter dopamine, which in turn can affect problem solving.{{cite book| vauthors = Revlin R |title=Human Cognition : Theory and Practice.|year=2007|publisher=Worth Pub|location=New York, NY|isbn=978-0-7167-5667-5|page=147|edition=International}}

Excessive alcohol use can result in brain damage which impairs working memory.{{cite journal | vauthors = van Holst RJ, Schilt T | title = Drug-related decrease in neuropsychological functions of abstinent drug users | journal = Current Drug Abuse Reviews | volume = 4 | issue = 1 | pages = 42–56 | date = March 2011 | pmid = 21466500 | doi = 10.2174/1874473711104010042 }} Alcohol has an effect on the blood-oxygen-level-dependent (BOLD) response. The BOLD response correlates increased blood oxygenation with brain activity, which makes this response a useful tool for measuring neuronal activity.{{cite journal | vauthors = Jacobus J, Tapert SF | title = Neurotoxic effects of alcohol in adolescence | journal = Annual Review of Clinical Psychology | volume = 9 | issue = 1 | pages = 703–721 | year = 2013 | pmid = 23245341 | pmc = 3873326 | doi = 10.1146/annurev-clinpsy-050212-185610 }} The BOLD response affects regions of the brain such as the basal ganglia and thalamus when performing a working memory task. Adolescents who start drinking at a young age show a decreased BOLD response in these brain regions.{{cite journal | vauthors = Weiland BJ, Nigg JT, Welsh RC, Yau WY, Zubieta JK, Zucker RA, Heitzeg MM | title = Resiliency in adolescents at high risk for substance abuse: flexible adaptation via subthalamic nucleus and linkage to drinking and drug use in early adulthood | journal = Alcoholism: Clinical and Experimental Research | volume = 36 | issue = 8 | pages = 1355–1364 | date = August 2012 | pmid = 22587751 | pmc = 3412943 | doi = 10.1111/j.1530-0277.2012.01741.x }} Alcohol dependent young women in particular exhibit less of a BOLD response in parietal and frontal cortices when performing a spatial working memory task.{{cite journal | vauthors = Tapert SF, Brown GG, Kindermann SS, Cheung EH, Frank LR, Brown SA | title = fMRI measurement of brain dysfunction in alcohol-dependent young women | journal = Alcoholism: Clinical and Experimental Research | volume = 25 | issue = 2 | pages = 236–245 | date = February 2001 | pmid = 11236838 | doi = 10.1111/j.1530-0277.2001.tb02204.x }} Binge drinking, specifically, can also affect one's performance on working memory tasks, particularly visual working memory.{{cite journal | vauthors = Ferrett HL, Carey PD, Thomas KG, Tapert SF, Fein G | title = Neuropsychological performance of South African treatment-naïve adolescents with alcohol dependence | journal = Drug and Alcohol Dependence | volume = 110 | issue = 1–2 | pages = 8–14 | date = July 2010 | pmid = 20227839 | pmc = 4456395 | doi = 10.1016/j.drugalcdep.2010.01.019 }}{{cite journal | vauthors = Crego A, Holguín SR, Parada M, Mota N, Corral M, Cadaveira F | title = Binge drinking affects attentional and visual working memory processing in young university students | journal = Alcoholism: Clinical and Experimental Research | volume = 33 | issue = 11 | pages = 1870–1879 | date = November 2009 | pmid = 19673739 | doi = 10.1111/j.1530-0277.2009.01025.x | hdl-access = free | hdl = 10347/16832 }} Additionally, there seems to be a gender difference in regards to how alcohol affects working memory. While women perform better on verbal working memory tasks after consuming alcohol compared to men, they appear to perform worse on spatial working memory tasks as indicated by less brain activity.{{cite journal | vauthors = Greenstein JE, Kassel JD, Wardle MC, Veilleux JC, Evatt DP, Heinz AJ, Roesch LL, Braun AR, Yates MC | display-authors = 6 | title = The separate and combined effects of nicotine and alcohol on working memory capacity in nonabstinent smokers | journal = Experimental and Clinical Psychopharmacology | volume = 18 | issue = 2 | pages = 120–128 | date = April 2010 | pmid = 20384423 | doi = 10.1037/a0018782 }}{{cite journal | vauthors = Squeglia LM, Schweinsburg AD, Pulido C, Tapert SF | title = Adolescent binge drinking linked to abnormal spatial working memory brain activation: differential gender effects | journal = Alcoholism: Clinical and Experimental Research | volume = 35 | issue = 10 | pages = 1831–1841 | date = October 2011 | pmid = 21762178 | pmc = 3183294 | doi = 10.1111/j.1530-0277.2011.01527.x }} Finally, age seems to be an additional factor. Older adults are more susceptible than others to the effects of alcohol on working memory.{{cite journal | vauthors = Boissoneault J, Sklar A, Prather R, Nixon SJ | title = Acute effects of moderate alcohol on psychomotor, set shifting, and working memory function in older and younger social drinkers | journal = Journal of Studies on Alcohol and Drugs | volume = 75 | issue = 5 | pages = 870–879 | date = September 2014 | pmid = 25208205 | pmc = 4161706 | doi = 10.15288/jsad.2014.75.870 }}

Individual differences in working-memory capacity are to some extent heritable; that is, about half of the variation between individuals is related to differences in their genes.{{cite journal | vauthors = Engelhardt LE, Mann FD, Briley DA, Church JA, Harden KP, Tucker-Drob EM | title = Strong genetic overlap between executive functions and intelligence | journal = Journal of Experimental Psychology. General | volume = 145 | issue = 9 | pages = 1141–1159 | date = September 2016 | pmid = 27359131 | pmc = 5001920 | doi = 10.1037/xge0000195 }}{{cite journal | vauthors = Ando J, Ono Y, Wright MJ | title = Genetic structure of spatial and verbal working memory | journal = Behavior Genetics | volume = 31 | issue = 6 | pages = 615–624 | date = November 2001 | pmid = 11838538 | doi = 10.1023/A:1013353613591 | s2cid = 39136550 }}{{cite journal | vauthors = Blokland GA, McMahon KL, Thompson PM, Martin NG, de Zubicaray GI, Wright MJ | title = Heritability of working memory brain activation | journal = The Journal of Neuroscience | volume = 31 | issue = 30 | pages = 10882–10890 | date = July 2011 | pmid = 21795540 | pmc = 3163233 | doi = 10.1523/jneurosci.5334-10.2011 }} The genetic component of variability of working-memory capacity is largely shared with that of fluid intelligence.

Little is known about which genes are related to the functioning of working memory. Within the theoretical framework of the multi-component model, one candidate gene has been proposed, namely ROBO1 for the hypothetical phonological loop component of working memory.{{cite journal | vauthors = Bates TC, Luciano M, Medland SE, Montgomery GW, Wright MJ, Martin NG | title = Genetic variance in a component of the language acquisition device: ROBO1 polymorphisms associated with phonological buffer deficits | journal = Behavior Genetics | volume = 41 | issue = 1 | pages = 50–57 | date = January 2011 | pmid = 20949370 | doi = 10.1007/s10519-010-9402-9 | s2cid = 13129473 }}

More recently another gene was found regarding working memory. Looking at genetically diverse mice, GPR12 was found in promoting a protein necessary for working memory. When they took mice that were performing worse on memory tests than their control mouse counterparts and increased their GPR12 proteins, those mice improved from 50% to 80%. That brought the low performance mice up to level similar to their control counterparts.{{Cite web | vauthors = Ramanujan K | date = 29 September 2020 |title=Gene links short-term memory to unexpected brain area|url=https://news.cornell.edu/stories/2020/09/gene-links-short-term-memory-unexpected-brain-area|access-date=2021-10-17|website=Cornell Chronicle|language=en}}

With the build up of prior work on mice such as testing the Formimidoyltransferase Cyclodeaminase (FTCD) gene in regards to the Morris water maze performance, testing out if there was a potential variation of genetic coding within the FTCD gene within humans was soon tested out. Results showed that a variation was found but varied depending on the age of the individual. In regards to the FTCD gene, it appeared that only children were affected by it. Working memory seemed to have a higher performance when the FTCD gene was present but had no similar affect to adults.{{cite journal | vauthors = Greenwood PM, Schmidt K, Lin MK, Lipsky R, Parasuraman R, Jankord R | title = A functional promoter variant of the human formimidoyltransferase cyclodeaminase (FTCD) gene is associated with working memory performance in young but not older adults | journal = Neuropsychology | volume = 32 | issue = 8 | pages = 973–984 | date = November 2018 | pmid = 29927301 | doi = 10.1037/neu0000470 | s2cid = 49350692 }}

Working memory capacity is correlated with learning outcomes in literacy and numeracy. Initial evidence for this relation comes from the correlation between working-memory capacity and reading comprehension, as first observed by Daneman and Carpenter (1980){{Cite journal|title = Individual differences in working memory and reading|journal = Journal of Verbal Learning and Verbal Behavior|date = 1980-08-01|pages = 450–466|volume = 19|issue = 4|doi = 10.1016/S0022-5371(80)90312-6| vauthors = Daneman M, Carpenter PA | s2cid=144899071 }} and confirmed in a later meta-analytic review of several studies.{{cite journal | vauthors = Daneman M, Merikle PM | title = Working memory and language comprehension: A meta-analysis | journal = Psychonomic Bulletin & Review | volume = 3 | issue = 4 | pages = 422–433 | date = December 1996 | pmid = 24213976 | doi = 10.3758/BF03214546 | doi-access = free }} Subsequent work found that working memory performance in primary school children accurately predicted performance in mathematical problem solving.{{Cite journal| vauthors = Swanson HL, Beebe-Frankenberger M |year=2004|title=The Relationship Between Working Memory and Mathematical Problem Solving in Children at Risk and Not at Risk for Serious Math Difficulties|journal=Journal of Educational Psychology|volume=96|issue=3|pages=471–491|doi=10.1037/0022-0663.96.3.471}} One longitudinal study showed that a child's working memory at 5 years old is a better predictor of academic success than IQ.{{cite journal | vauthors = Alloway TP, Alloway RG | title = Investigating the predictive roles of working memory and IQ in academic attainment | journal = Journal of Experimental Child Psychology | volume = 106 | issue = 1 | pages = 20–29 | date = May 2010 | pmid = 20018296 | doi = 10.1016/j.jecp.2009.11.003 | hdl-access = free | s2cid = 13854871 | hdl = 20.500.11820/8a871fe8-5117-4a4b-8d6c-74277e9a79e1 | url = https://www.research.ed.ac.uk/en/publications/8a871fe8-5117-4a4b-8d6c-74277e9a79e1 }}

A randomized controlled study of 580 children in Germany indicated that working memory training at age six had a significant positive effect in spatial working memory immediately after training, and that the effect gradually transferred to other areas, with significant and meaningful increases in reading comprehension, mathematics (geometry), and IQ (measured by Raven matrices). Additionally, a marked increase in ability to inhibit impulses was detected in the follow-up after one year, measured as a higher score in the Go-No Go task. Four years after the treatment, the effects persisted and was captured as a 16 percentage point higher acceptance rate to the academic track (German Gymnasium), as compared to the control group.

In a large-scale screening study, one in ten children in mainstream classrooms were identified with working memory deficits. The majority of them performed very poorly in academic achievements, independent of their IQ.{{cite journal | vauthors = Alloway TP, Gathercole SE, Kirkwood H, Elliott J | title = The cognitive and behavioral characteristics of children with low working memory | journal = Child Development | volume = 80 | issue = 2 | pages = 606–621 | year = 2009 | pmid = 19467014 | doi = 10.1111/j.1467-8624.2009.01282.x | hdl-access = free | hdl = 1893/978 | s2cid = 14481660 }} Similarly, working memory deficits have been identified in national curriculum low-achievers as young as seven years of age.{{cite journal | vauthors = Gathercole SE, Pickering SJ | title = Working memory deficits in children with low achievements in the national curriculum at 7 years of age | journal = The British Journal of Educational Psychology | volume = 70 | issue = 2 | pages = 177–194 | date = June 2000 | pmid = 10900777 | doi = 10.1348/000709900158047 }} Without appropriate intervention, these children lag behind their peers. A recent study of 37 school-age children with significant learning disabilities has shown that working memory capacity at baseline measurement, but not IQ, predicts learning outcomes two years later.{{Cite journal| vauthors = Alloway TP |year=2009 |journal=European Journal of Psychological Assessment |volume=25 |issue=2 |pages=92–8 |doi=10.1027/1015-5759.25.2.92 |title=Working Memory, but Not IQ, Predicts Subsequent Learning in Children with Learning Difficulties|hdl=1893/1005 |hdl-access=free }} This suggests that working memory impairments are associated with low learning outcomes and constitute a high risk factor for educational underachievement for children. In children with learning disabilities such as dyslexia, ADHD, and developmental coordination disorder, a similar pattern is evident.{{cite book | vauthors = Pickering SJ |chapter=Working memory in dyslexia |pages=7–40 | veditors = Alloway TP, Gathercole SE | title = Working memory and neurodevelopmental disorders | publisher = Psychology Press | year = 2006 | location = New York, NY | isbn = 978-1-84169-560-0 |oclc = 63692704 |doi=10.4324/9780203013403 }}{{cite book | vauthors = Wagner RK, Muse A |chapter=Short-term memory deficits in developmental dyslexia |pages=41–57 | veditors = Alloway TP, Gathercole SE | title = Working memory and neurodevelopmental disorders | publisher = Psychology Press | year = 2006 | location = New York, NY | isbn = 978-1-84169-560-0 |oclc = 63692704 |doi=10.4324/9780203013403 }}{{cite book | vauthors = Roodenrys S |chapter=Working memory function in attention deficit hyperactivity disorder |pages=187–212 | veditors = Alloway TP, Gathercole SE | title = Working memory and neurodevelopmental disorders | publisher = Psychology Press | year = 2006 | location = New York, NY | isbn = 978-1-84169-560-0 |oclc = 63692704 |doi=10.4324/9780203013403 }}{{cite book | vauthors = Alloway TP |chapter=Working memory skills in children with developmental coordination disorder |pages=161–185 | veditors = Alloway TP, Gathercole SE | title = Working memory and neurodevelopmental disorders | publisher = Psychology Press | year = 2006 | location = New York, NY | isbn = 978-1-84169-560-0 |oclc = 63692704 |doi=10.4324/9780203013403 }}

There is some evidence that optimal working memory performance links to the neural ability to focus attention on task-relevant information and to ignore distractions,{{cite journal | vauthors = Zanto TP, Gazzaley A | title = Neural suppression of irrelevant information underlies optimal working memory performance | journal = The Journal of Neuroscience | volume = 29 | issue = 10 | pages = 3059–3066 | date = March 2009 | pmid = 19279242 | pmc = 2704557 | doi = 10.1523/JNEUROSCI.4621-08.2009 }} and that practice-related improvement in working memory is due to increasing these abilities.{{cite journal | vauthors = Berry AS, Zanto TP, Rutman AM, Clapp WC, Gazzaley A | title = Practice-related improvement in working memory is modulated by changes in processing external interference | journal = Journal of Neurophysiology | volume = 102 | issue = 3 | pages = 1779–1789 | date = September 2009 | pmid = 19587320 | pmc = 2746773 | doi = 10.1152/jn.00179.2009 }} One line of research suggests a link between the working memory capacities of a person and their ability to control the orientation of attention to stimuli in the environment.{{cite journal | vauthors = Fukuda K, Vogel EK | title = Human variation in overriding attentional capture | journal = The Journal of Neuroscience | volume = 29 | issue = 27 | pages = 8726–8733 | date = July 2009 | pmid = 19587279 | pmc = 6664881 | doi = 10.1523/JNEUROSCI.2145-09.2009 }} Such control enables people to attend to information important for their current goals, and to ignore goal-irrelevant stimuli that tend to capture their attention due to their sensory saliency (such as an ambulance siren). The direction of attention according to one's goals is assumed to rely on "top-down" signals from the pre-frontal cortex (PFC) that biases processing in posterior cortical areas.{{cite journal | vauthors = Desimone R, Duncan J | title = Neural mechanisms of selective visual attention | journal = Annual Review of Neuroscience | volume = 18 | pages = 193–222 | year = 1995 | pmid = 7605061 | doi = 10.1146/annurev.ne.18.030195.001205 | s2cid = 14290580 }} Capture of attention by salient stimuli is assumed to be driven by "bottom-up" signals from subcortical structures and the primary sensory cortices.{{cite journal | vauthors = Yantis S, Jonides J | title = Abrupt visual onsets and selective attention: voluntary versus automatic allocation | journal = Journal of Experimental Psychology. Human Perception and Performance | volume = 16 | issue = 1 | pages = 121–134 | date = February 1990 | pmid = 2137514 | doi = 10.1037/0096-1523.16.1.121 }} The ability to override "bottom-up" capture of attention differs between individuals, and this difference has been found to correlate with their performance in a working-memory test for visual information. Another study, however, found no correlation between the ability to override attentional capture and measures of more general working-memory capacity.{{cite journal | vauthors = Mall JT, Morey CC, Wolff MJ, Lehnert F | title = Visual selective attention is equally functional for individuals with low and high working memory capacity: evidence from accuracy and eye movements | journal = Attention, Perception, & Psychophysics | volume = 76 | issue = 7 | pages = 1998–2014 | date = October 2014 | pmid = 24402698 | doi = 10.3758/s13414-013-0610-2 | s2cid = 25772094 | url = https://orca.cardiff.ac.uk/id/eprint/105362/1/Morey.%20Visual%20selective.pdf }}

An impairment of working memory functioning is normally seen in several neural disorders:

Several authorsBarkley; Castellanos and Tannock; Pennington and Ozonoff; Schachar (according to the source) have proposed that symptoms of ADHD arise from a primary deficit in a specific executive function (EF) domain such as working memory, response inhibition or a more general weakness in executive control.{{cite journal | vauthors = Willcutt EG, Doyle AE, Nigg JT, Faraone SV, Pennington BF | title = Validity of the executive function theory of attention-deficit/hyperactivity disorder: a meta-analytic review | journal = Biological Psychiatry | volume = 57 | issue = 11 | pages = 1336–1346 | date = June 2005 | pmid = 15950006 | doi = 10.1016/j.biopsych.2005.02.006 | s2cid = 9520878 }} A meta-analytical review cites several studies that found significant lower group results for ADHD in spatial and verbal working memory tasks, and in several other EF tasks. However, the authors concluded that EF weaknesses neither are necessary nor sufficient to cause all cases of ADHD.

Several neurotransmitters, such as dopamine and glutamate may be involved in both ADHD and working memory. Both are associated with the frontal brain, self-direction and self-regulation, but cause–effect have not been confirmed, so it is unclear whether working memory dysfunction leads to ADHD, or ADHD distractibility leads to poor functionality of working memory, or if there is some other connection.{{cite journal | vauthors = Kofler MJ, Rapport MD, Bolden J, Altro TA | title = Working Memory as a Core Deficit in ADHD: Preliminary Findings and Implications. | journal = The ADHD Report | date = December 2008 | volume = 16 | issue = 6 | pages = 8–14 | doi = 10.1521/adhd.2008.16.6.8 | url = http://guilfordjournals.com/doi/abs/10.1521/adhd.2008.16.6.8 | url-access = subscription }}{{cite journal | vauthors = Clark L, Blackwell AD, Aron AR, Turner DC, Dowson J, Robbins TW, Sahakian BJ | title = Association between response inhibition and working memory in adult ADHD: a link to right frontal cortex pathology? | journal = Biological Psychiatry | volume = 61 | issue = 12 | pages = 1395–1401 | date = June 2007 | pmid = 17046725 | doi = 10.1016/j.biopsych.2006.07.020 | s2cid = 21199314 }}{{cite journal| vauthors = Roodenrys S, Koloski N, Grainger J |year=2001|title=Working memory function in attention deficit hyperactivity disordered and reading disabled children|journal=British Journal of Developmental Psychology|volume=19|issue=3|pages=325–337|doi=10.1348/026151001166128|issn=0261-510X|doi-access=free}}

Patients with Parkinson's show signs of a reduced verbal function of working memory. They wanted to find if the reduction is due to a lack of ability to focus on relevant tasks, or a low amount of memory capacity. Twenty-one patients with Parkinson's were tested in comparison to the control group of 28 participants of the same age. The researchers found that both hypotheses were the reason working memory function is reduced which did not fully agree with their hypothesis that it is either one or the other.{{cite journal | vauthors = Lee EY, Cowan N, Vogel EK, Rolan T, Valle-Inclán F, Hackley SA | title = Visual working memory deficits in patients with Parkinson's disease are due to both reduced storage capacity and impaired ability to filter out irrelevant information | journal = Brain | volume = 133 | issue = 9 | pages = 2677–2689 | date = September 2010 | pmid = 20688815 | pmc = 2929336 | doi = 10.1093/brain/awq197 }}

As Alzheimer's disease becomes more serious, less working memory functions. In addition to deficits in episodic memory, Alzheimer's disease is associated with impairments in visual short-term memory, assessed using delayed reproduction tasks.{{cite journal | vauthors = Zokaei N, Sillence A, Kienast A, Drew D, Plant O, Slavkova E, Manohar SG, Husain M | display-authors = 6 | title = Different patterns of short-term memory deficit in Alzheimer's disease, Parkinson's disease and subjective cognitive impairment | journal = Cortex; A Journal Devoted to the Study of the Nervous System and Behavior | volume = 132 | pages = 41–50 | date = November 2020 | pmid = 32919108 | pmc = 7651994 | doi = 10.1016/j.cortex.2020.06.016 }}{{cite journal | vauthors = Liang Y, Pertzov Y, Nicholas JM, Henley SM, Crutch S, Woodward F, Leung K, Fox NC, Husain M | display-authors = 6 | title = Visual short-term memory binding deficit in familial Alzheimer's disease | journal = Cortex; A Journal Devoted to the Study of the Nervous System and Behavior | volume = 78 | pages = 150–164 | date = May 2016 | pmid = 27085491 | pmc = 4865502 | doi = 10.1016/j.cortex.2016.01.015 }}{{cite book |doi=10.1007/7854_2019_103 |chapter=Working Memory in Alzheimer's Disease and Parkinson's Disease |title=Processes of Visuospatial Attention and Working Memory |series=Current Topics in Behavioral Neurosciences |date=2019 |last1=Zokaei |first1=Nahid |last2=Husain |first2=Masud |volume=41 |pages=325–344 |pmid=31347008 |isbn=978-3-030-31025-7 }} These investigations point to a deficit in visual feature binding as an important component of the deficit in Alzheimer's disease. There is one study that focuses on the neural connections and fluidity of working memory in mice brains. Half of the mice were given an injection that mimicked the effects of Alzheimer's, and the other half were not. Then the mice were expected to go through a maze that is a task to test working memory. The study helps answer questions about how Alzheimer's can deteriorate the working memory and ultimately obliterate memory functions.{{cite journal | vauthors = Liu T, Bai W, Yi H, Tan T, Wei J, Wang J, Tian X | title = Functional connectivity in a rat model of Alzheimer's disease during a working memory task | journal = Current Alzheimer Research | volume = 11 | issue = 10 | pages = 981–991 | date = December 2014 | pmid = 25387338 | doi = 10.2174/1567205011666141107125912 }}

A group of researchers hosted a study that researched the function and connectivity of working memory over a 30-month longitudinal experiment. It found that there were certain places in the brain where most connectivity was decreased in pre-Huntington diseased patients, in comparison to the control group that remained consistently functional.{{cite journal | vauthors = Poudel GR, Stout JC, Domínguez DJ, Gray MA, Salmon L, Churchyard A, Chua P, Borowsky B, Egan GF, Georgiou-Karistianis N | display-authors = 6 | title = Functional changes during working memory in Huntington's disease: 30-month longitudinal data from the IMAGE-HD study | journal = Brain Structure & Function | volume = 220 | issue = 1 | pages = 501–512 | date = January 2015 | pmid = 24240602 | doi = 10.1007/s00429-013-0670-z | s2cid = 15385419 }}

A recent study by Li and colleagues showed evidence that the same brain regions responsible for working memory are also responsible for how much humans trust those memories. In the past, studies have shown that individuals can evaluate how much they trust their own memories, but how humans can do this was largely unknown. Using spatial memory tests and fMRI scans, they processed where and when the information was being stored and used this data to determine memory errors. They also asked the participants to express how uncertain they were about their memories. With both sets of information, the researchers could conclude that memory and the trust in that memory are stored within the same brain region.{{Cite web| vauthors = Devitt J |title=Scientists Pinpoint the Uncertainty of Our Working Memory|url=https://www.nyu.edu/about/news-publications/news/2021/september/scientists-pinpoint-the-uncertainty-of-our-working-memory-.html|website=NYU}}

• Atkinson–Shiffrin memory model
• {{Section link|Prefrontal cortex|Attention and memory}}
• Fuzzy-trace theory
• Intermediate-term memory
• Memory and aging
• Prefrontal cortex basal ganglia working memory (PBWM)
• Cognitive architecture
• Tim Shallice
• Working memory (autism)

{{Reflist|33em}}

{{Memory}}

{{Dyslexia}}

{{Authority control}}

Category:Memory

Category:Problem solving

Category:Human behavior