visual modularity

Akinetopsia, a term coined by Semir Zeki,{{Cite journal|last=ZEKI|first=S.|title=Cerebral Akinetopsia (Visual Motion Blindness)|date=1991-04-01|url=https://doi.org/10.1093/brain/114.2.811|journal=Brain|volume=114|issue=2|pages=811–824|doi=10.1093/brain/114.2.811|pmid=2043951|issn=0006-8950}} refers to an intriguing condition brought about by damage to the Extrastriate cortex MT+ (also known as area V5) that renders humans and monkeys unable to perceive motion, seeing the world in a series of static "frames" instead{{cite journal|vauthors=Zihl J, von Cramon D, Mai N, Schmid C |year=1991|title=Disturbance of movement vision after bilateral posterior brain damage|journal=Brain|issue=144|doi=10.1093/brain/114.5.2235|pages=2235–2252|volume=114|pmid=1933243}}{{cite journal|last=Zihl|first=J. |author2=von Cramon, D.Y. |author3=Mai, N.|year=1983|title=Selective disturbances of movement vision after bilateral brain damage|journal=Brain|issue=2|doi=10.1093/brain/106.2.525-a|pages=313–340|volume=106}}{{cite journal |vauthors=Hess RH, Baker CL, Zihl J |title=The "motion-blind" patient: low-level spatial and temporal filters |journal=J. Neurosci. |volume=9 |issue=5 |pages=1628–40 |year=1989 |pmid=2723744 |doi= 10.1523/JNEUROSCI.09-05-01628.1989|doi-access=free |pmc=6569833 }}{{cite journal | title=Residual motion perception in a" motion-blind" patient, assessed with limited-lifetime random dot stimuli | vauthors=Baker CL, Hess RF, Zihl J | journal=Journal of Neuroscience | year=1991 | volume=11 | issue=2 | pages=454–461 | pmid=1992012| doi=10.1523/JNEUROSCI.11-02-00454.1991 | doi-access=free | pmc=6575225 }} and indicates that there might be a "motion centre" in the brain. Of course, such data can only indicate that this area is at least necessary to motion perception, not that it is sufficient; however, other evidence has shown the importance of this area to primate motion perception. Specifically, physiological, neuroimaging, perceptual, electrical- and transcranial magnetic stimulation evidence (Table 1) all come together on the area V5/hMT+. Converging evidence of this type is supportive of a module for motion processing. However, this view is likely to be incomplete: other areas are involved with motion perception, including V1,{{cite journal|last=Orban|first=G.A.|author2=Kennedy, H. |author3=Bullier, J. |year=1986|title=Velocity sensitivity and direction selectivity of neurons in areas V1 and V2 of the monkey: influence of eccentricity|journal=Journal of Neurophysiology|volume=56|issue=2|doi=10.1016/j.jphysparis.2004.03.004|pages=462–480|pmid=3760931|s2cid=26116687 }}{{cite journal|last=Movshon|first=J.A.|author2=Newsome, W.T. |year=1996|title=Visual response properties of striate cortical neurons projecting to area MT in macaque monkeys|journal=Journal of Neuroscience|volume=16|issue=23|pages=7733–7741|pmid=8922429|doi=10.1523/JNEUROSCI.16-23-07733.1996|pmc=6579106|doi-access=free}}{{cite journal|last=Born|first=R.T.|author2=Bradley, D.C. |year=2005|title=Structure and function of visual area MT|journal=Annual Review of Neuroscience|volume=28|pages=157–189|pmid=16022593|doi=10.1146/annurev.neuro.26.041002.131052}} V2 and V3a {{cite journal|last=Grill-Spector|first=K.|author2=Malach, R. |year=2004|title=The Human Visual Cortex|journal=Annual Review of Neuroscience|volume=27|pages=649–677|doi=10.1146/annurev.neuro.27.070203.144220|pmid=15217346}} and areas surrounding V5/hMT+ (Table 2). A recent fMRI study put the number of motion areas at twenty-one.{{cite journal|vauthors=Stiers P, Peeters R, Lagae L, Van Hecke P, Sunaert S |title=Mapping multiple visual areas in the human brain with a short fMRI sequence|journal=NeuroImage|date=Jan 1, 2006|volume=29|issue=1|pages=74–89|doi=10.1016/j.neuroimage.2005.07.033|pmid=16154766|s2cid=24485857 |doi-access=free}} Clearly, this constitutes a stream of diverse anatomical areas. The extent to which this is ‘pure’ is in question: with Akinetopsia come severe difficulties in obtaining structure from motion.{{cite journal|last=Rizzo|first=Matthew|author2-link=Mark Nawrot|author2=Nawrot, Mark |author3=Zihl, Josef |title=Motion and shape perception in cerebral akinetopsia|journal=Brain|date=1 January 1995|volume=118|issue=5|pages=1105–1127|doi=10.1093/brain/118.5.1105|pmid=7496774}} V5/hMT+ has since been implicated in this function{{cite journal|last=Grunewald|first=A|author2=Bradley, DC |author3=Andersen, RA |title=Neural correlates of structure-from-motion perception in macaque V1 and MT|journal=The Journal of Neuroscience|date=Jul 15, 2002|volume=22|issue=14|pages=6195–207|pmid=12122078|doi=10.1523/JNEUROSCI.22-14-06195.2002|pmc=6757912|doi-access=free}} as well as determining depth.{{cite journal|last=DeAngelis|first=GC|author2=Cumming, BG |author3=Newsome, WT |title=Cortical area MT and the perception of stereoscopic depth|journal=Nature|date=Aug 13, 1998|volume=394|issue=6694|pages=677–80|doi=10.1038/29299|pmid=9716130|bibcode=1998Natur.394..677D |s2cid=4419753 }} Thus the current evidence suggests that motion processing occurs in a modular stream, although with a role in form and depth perception at higher levels.

Similar converging evidence suggests modularity for color. Beginning with Gowers’ finding{{cite book|last=Gowers|first=W.|title=A manual of diseases of the brain|year=1888|publisher=J & A Churchill}} that damage to the fusiform/lingual gyri in occipitotemporal cortex correlates with a loss in color perception (achromatopsia), the notion of a "color centre" in the primate brain has had growing support.{{cite journal|last=Meadows|first=JC|title=Disturbed perception of colours associated with localized cerebral lesions|journal=Brain: A Journal of Neurology|date=Dec 1974|volume=97|issue=4|pages=615–32|doi=10.1093/brain/97.1.615|pmid=4547992}}{{cite journal|last=Zeki|first=S.|title=Parallelism and Functional Specialization in Human Visual Cortex|journal=Cold Spring Harbor Symposia on Quantitative Biology|date=1 January 1990|volume=55|pages=651–661|doi=10.1101/SQB.1990.055.01.062|pmid=2132845}}{{cite book|last=Grüsser and Landis|title=Visual agnosias and other disturbances of visual perception and cognition|year=1991|publisher=MacMillan|pages=297–303}} Again, such clinical evidence only implies that this region is critical to color perception, and nothing more. Other evidence, however, including neuroimaging{{Cite journal |author1=Bartels, A. |author2=Zeki, S. |name-list-style=amp |title=Brain dynamics during natural viewing conditions - a new guide for mapping connectivity in vivo |journal=NeuroImage |volume=24 |issue=2 |pages=339–349 |year=2005 |doi=10.1016/j.neuroimage.2004.08.044 |quote=no |pmid=15627577|s2cid=16882384 }}{{Cite journal |author1=Bartels, A. |author2=Zeki, S. |name-list-style=amp |title=The architecture of the colour centre in the human visual brain: new results and a review |journal=European Journal of Neuroscience |volume=12 |issue=1 |pages=172–193 |year=2000 |doi=10.1046/j.1460-9568.2000.00905.x |quote=no |pmid=10651872|s2cid=6787155 }} and physiology{{cite journal|last=Wachtler|first=T|author2=Sejnowski, TJ |author3=Albright, TD |title=Representation of color stimuli in awake macaque primary visual cortex|journal=Neuron|date=Feb 20, 2003|volume=37|issue=4|pages=681–91|doi=10.1016/S0896-6273(03)00035-7|pmid=12597864|pmc=2948212}}{{cite journal|last=Kusunoki|first=M|author2=Moutoussis, K |author3=Zeki, S |title=Effect of background colors on the tuning of color-selective cells in monkey area V4|journal=Journal of Neurophysiology|date=May 2006|volume=95|issue=5|pages=3047–59|doi=10.1152/jn.00597.2005|pmid=16617176}} converges on V4 as necessary to color perception. A recent meta-analysis has also shown a specific lesion common to achromats corresponding to V4.{{cite journal|last=Bouvier|first=S. E.|author2=Engel, SA |title=Behavioral Deficits and Cortical Damage Loci in Cerebral Achromatopsia|journal=Cerebral Cortex|date=27 April 2005|volume=16|issue=2|pages=183–191|doi=10.1093/cercor/bhi096|pmid=15858161|doi-access=free}} From another direction altogether it has been found that when synaesthetes experience color by a non-visual stimulus, V4 is active.{{cite journal|last=Rich|first=AN|author2=Williams, MA |author3=Puce, A |author4=Syngeniotis, A |author5=Howard, MA |author6=McGlone, F |author7= Mattingley, JB |title=Neural correlates of imagined and synaesthetic colours|journal=Neuropsychologia|year=2006|volume=44|issue=14|pages=2918–25|doi=10.1016/j.neuropsychologia.2006.06.024|pmid=16901521|s2cid=6047634 }}{{cite journal|last=Sperling|first=JM|author2=Prvulovic, D |author3=Linden, DE |author4=Singer, W |author5= Stirn, A |title=Neuronal correlates of colour-graphemic synaesthesia: a fMRI study|journal=Cortex|date=Feb 2006|volume=42|issue=2|pages=295–303|doi=10.1016/S0010-9452(08)70355-1|pmid=16683504|s2cid=1559357 }} On the basis of this evidence it would seem that color processing is modular. However, as with motion processing it is likely that this conclusion is inaccurate. Other evidence shown in Table 3 implies different areas’ involvement with color. It may thus be more instructive to consider a multistage color processing stream from the retina through to cortical areas including at least V1, V2, V4, PITd and TEO. Consonant with motion perception, there appears to be a constellation of areas drawn upon for color perception. In addition, V4 may have a special, but not exclusive, role. For example, single cell recording has shown that only V4 cells respond to the color of a stimuli rather than its waveband, whereas other areas involved with color do not.

Another clinical case that would a priori suggest a module for modularity in visual processing is visual agnosia. The well studied patient DF is unable to recognize or discriminate objects{{cite journal|last=Mishkin|first=Mortimer|author2=Ungerleider, Leslie G. |author3=Macko, Kathleen A. |title=Object vision and spatial vision: two cortical pathways|journal=Trends in Neurosciences|year=1983|volume=6|pages=414–417|doi=10.1016/0166-2236(83)90190-X|s2cid=15565609 }} owing to damage in areas of the lateral occipital cortex although she can see scenes without problem – she can literally see the forest but not the trees.{{cite journal|last=Steeves|first=Jennifer K.E.|author2=Culham, Jody C. |author3=Duchaine, Bradley C. |author4=Pratesi, Cristiana Cavina |author5=Valyear, Kenneth F. |author6=Schindler, Igor |author7=Humphrey, G. Keith |author8=Milner, A. David |author9= Goodale, Melvyn A. |title=The fusiform face area is not sufficient for face recognition: Evidence from a patient with dense prosopagnosia and no occipital face area|journal=Neuropsychologia|year=2006|volume=44|issue=4|pages=594–609|doi=10.1016/j.neuropsychologia.2005.06.013|pmid=16125741|s2cid=460887 |url=http://dro.dur.ac.uk/6186/1/6186.pdf}} Neuroimaging of intact individuals reveals strong occipito-temporal activation during object presentation and greater activation still for object recognition.{{cite journal|last=Grill-Spector|first=Kalanit|author2=Ungerleider, Leslie G. |author3=Macko, Kathleen A. |title=The neural basis of object perception|journal=Current Opinion in Neurobiology|year=2003|volume=13|issue=3|pages=159–166|doi=10.1016/S0959-4388(03)00060-6|pmid=12744968|s2cid=54383849 |doi-access=free}} Of course, such activation could be due to other processes, such as visual attention. However, other evidence that shows a tight coupling of perceptual and physiological changes{{cite journal|last=Sheinberg|first=DL|author2=Logothetis, NK |title=Noticing familiar objects in real world scenes: the role of temporal cortical neurons in natural vision|journal=The Journal of Neuroscience|date=Feb 15, 2001|volume=21|issue=4|pages=1340–50|pmid=11160405|doi=10.1523/JNEUROSCI.21-04-01340.2001|pmc=6762229|doi-access=free}} suggests activation in this area does underpin object recognition. Within these regions are more specialized areas for face or fine grained analysis,{{cite journal|last=Gauthier|first=I|author2=Skudlarski, P |author3=Gore, JC |author4= Anderson, AW |title=Expertise for cars and birds recruits brain areas involved in face recognition|journal=Nature Neuroscience|date=Feb 2000|volume=3|issue=2|pages=191–7|doi=10.1038/72140|pmid=10649576|s2cid=15752722}} place perception{{cite journal|last=Epstein|first=R|author2=Kanwisher, N |title=A cortical representation of the local visual environment|journal=Nature|date=Apr 9, 1998|volume=392|issue=6676|pages=598–601|doi=10.1038/33402|pmid=9560155|bibcode=1998Natur.392..598E|s2cid=920141}} and human body perception.{{cite journal|last=Downing|first=PE|author2=Jiang, Y |author3=Shuman, M |author4= Kanwisher, N |title=A cortical area selective for visual processing of the human body|journal=Science|date=Sep 28, 2001|volume=293|issue=5539|pages=2470–3|doi=10.1126/science.1063414|pmid=11577239|bibcode=2001Sci...293.2470D |citeseerx=10.1.1.70.6526|s2cid=1564641 }} Perhaps some of the strongest evidence for the modular nature of these processing systems is the double dissociation between object- and face (prosop-) agnosia. However, as with color and motion, early areas (see for a comprehensive review) are implicated too, lending support to the idea of a multistage stream terminating in the inferotemporal cortex rather than an isolated module.

One of the first uses of the term "module" or "modularity" occurs in the influential book "Modularity of Mind" by philosopher Jerry Fodor.{{cite book|last=Fodor|first=Jerry A.|title=The modularity of mind : an essay on faculty psychology|year=1989|publisher=MIT Press|location=Cambridge, Mass. [ u.a.]|isbn=978-0-262-56025-2|edition=6. printing.}} A detailed application of this idea to the case of vision was published by Pylyshyn (1999), who argued that there is a significant part of vision that is not responsive to beliefs and is "cognitively impenetrable".{{cite journal|last=Pylyshyn|first=Z|title=Is vision continuous with cognition? The case for cognitive impenetrability of visual perception|journal=The Behavioral and Brain Sciences|date=Jun 1999|volume=22|issue=3|pages=341–65; discussion 366–423|pmid=11301517|doi=10.1017/s0140525x99002022|s2cid=9482993}}

Much of the confusion concerning modularity exists in neuroscience because there is evidence for specific areas (e.g. V4 or V5/hMT+) and the concomitant behavioral deficits following brain insult (thus taken as evidence for modularity). In addition, evidence shows other areas are involved and that these areas subserve processing of multiple properties (e.g. V1{{cite journal|last=Leventhal|first=AG|author2=Thompson, KG |author3=Liu, D |author4=Zhou, Y |author5= Ault, SJ |title=Concomitant sensitivity to orientation, direction, and color of cells in layers 2, 3, and 4 of monkey striate cortex|journal=The Journal of Neuroscience|date=Mar 1995|volume=15|issue=3 Pt 1|pages=1808–18|pmid=7891136|doi=10.1523/JNEUROSCI.15-03-01808.1995|pmc=6578154|doi-access=free}}) (thus taken as evidence against modularity). That these streams have the same implementation in early visual areas, like V1, is not inconsistent with a modular viewpoint: to adopt the canonical analogy in cognition, it is possible for different software to run on the same hardware. A consideration of psychophysics and neuropsychological data would suggest support for this. For example, psychophysics has shown that percepts for different properties are realized asynchronously. In addition, although achromats experience other cognitive defects{{cite journal|last=Gegenfurtner|first=Karl R.|title=Sensory systems: Cortical mechanisms of colour vision|journal=Nature Reviews Neuroscience|year=2003|volume=4|issue=7|pages=563–572|doi=10.1038/nrn1138|pmid=12838331|s2cid=11505913 }} they do not have motion deficits when their lesion is restricted to V4, or total loss of form perception.{{cite journal|last=Zeki|first=S|title=The Ferrier Lecture 1995 behind the seen: the functional specialization of the brain in space and time|journal=Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences|date=Jun 29, 2005|volume=360|issue=1458|pages=1145–83|doi=10.1098/rstb.2005.1666|pmid=16147515|pmc=1609195}} Relatedly, Zihl and colleagues' akinetopsia patient shows no deficit to color or object perception (although deriving depth and structure from motion is problematic, see above) and object agnostics do not have damaged motion or color perception, making the three disorders triply dissociable. Taken together this evidence suggests that even though distinct properties may employ the same early visual areas they are functionally independent. Furthermore, that the intensity of subjective perceptual experience (e.g. color) correlates with activity in these specific areas (e.g. V4), the recent evidence that synaesthetes show V4 activation during the perceptual experience of color, as well as the fact that damage to these areas results in concomitant behavioral deficits (the processing may be occurring but perceivers do not have access to the information) are all evidence for visual modularity.

• Heautoscopy
• Modularity
• Society of Mind which proposes the mind is made up of agents
• Two streams hypothesis

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Category:Cognitive neuroscience

Category:Cognitive science

Category:Visual system