microsaccade

The role of microsaccades in visual perception has been a highly debated topic that is still largely unresolved. It has been proposed{{by whom|date=March 2019}} that microsaccades correct displacements in eye position produced by drifts, although non-corrective microsaccades also occur. Some work has suggested that microsaccades are directly correlated with the perception of illusory motion.[http://www.physorg.com/news145621013.html "Optical illusions: caused by eye or brain?"][https://www.sciencedaily.com/releases/2008/11/081120183733.htm 200-year-old Scientific Debate Involving Visual Illusions][http://www.eurekalert.org/pub_releases/2009-03/sjha-ttb030309.php The truth behind 'Where's Waldo?'] Although microsaccades can enhance vision of fine spatial detail,Rucci, M., Iovin, R., Poletti, M., Santini, F. (2007). [http://www.nature.com/nature/journal/v447/n7146/abs/nature05866.html "Miniature Eye Movements Enhance Fine Spatial Detail."] Nature,447(7146), 851-854.{{cite web |url= http://news.bbc.co.uk/2/hi/health/6745443.stm|title= Eye flickers key for fine detail |date=June 2007|publisher= BBC News}} they can also impair visual perception in that they are associated with saccadic suppression.{{cite journal |last1=Beeler |first1=G. W. |title=Visual threshold changes resulting from spontaneous saccadic eye movements |journal=Vision Research |date=1967 |volume=7|issue=9 |pages=769–75 |doi=10.1016/0042-6989(67)90039-9 |pmid=5608665 }} Microsaccades are also believed to be important for preventing the retinal image from fading.{{cite book |last1=Alexander |first1=R. G. |last2=Martinez-Conde |first2=S |title=Eye Movement Research |date=2019 |publisher=Springer, Cham |chapter=Fixational eye movements |pages=73–115}}

Microsaccades are tied to complex visual processing like reading. The specific timing pattern of microsaccades in humans changes during reading based on the structure of the word being read.{{cite journal |last1=Yablonski |first1=M |last2=Polat |first2=U |last3=Bonneh |first3=YS |last4=Ben-Shachar |first4=M |title=Microsaccades are sensitive to word structure: A novel approach to study language processing |journal=Scientific Reports |date=21 June 2017 |volume=7 |issue=1 |pages=3999 |doi=10.1038/s41598-017-04391-4 |pmid=28638094 |pmc=5479819 |bibcode=2017NatSR...7.3999Y }}{{cite book |last1=Krauzlis |first1=Richard J. |title=Fundamental Neuroscience |date=2013 |publisher=Academic Press |pages=697–714 |edition=4 |doi=10.1016/B978-0-12-385870-2.00032-9 |chapter=Eye Movements |isbn=9780123858702 }}

Experiments in neurophysiology from different laboratories showed that fixational eye movements, particularly microsaccades, strongly modulate the activity of neurons in the visual areas of the macaque brain. In the lateral geniculate nucleus (LGN) and the primary visual cortex (V1), microsaccades can move a

stationary stimulus in and out of a neuron's receptive field, thereby producing transient neural responses.{{cite journal |last1=Rucci |first1=Michele |last2=Edelman |first2=Gerald M. |last3=Wray |first3=Jonathan |title=Modeling LGN responses during free-viewing: A possible role of microscopic eye movements in the refinement of cortical orientation selectivity |journal=Journal of Neuroscience |date=2000 |volume=20 |issue=12 |pages=4708–4720 | pmc=6772442| doi=10.1523/JNEUROSCI.20-12-04708.2000|pmid=10844040 |doi-access=free }}{{cite journal |last1=Leopold |first1=D. A. |last2=Logothetis |first2=N. K. |title=Microsaccades differentially modulate neural activity in the striate and extrastriate visual cortex |journal=Experimental Brain Research |date=1998 |volume=123 |issue=3|pages=341–5 |doi=10.1007/s002210050577 |pmid=9860273 |s2cid=18751039 }} Microsaccades might account for much of the response variability of neurons in visual area V1 of the awake monkey.

Current research in visual neuroscience and psychophysics is investigating how microsaccades relate to fixation correction, memory,{{cite journal |last1=Martinez-Conde |first1=S |last2=Alexander |first2=R |title=A gaze bias in the mind's eye |journal=Nature Human Behaviour |volume=3 |issue=5 |pages=424–425 |date=2019 |doi=10.1038/s41562-019-0546-1 |pmid=31089295 |s2cid=71148025 }} control of binocular fixation disparity{{cite journal |last1=Valsecchi |first1=Matteo |last2=Gegenfurtner |first2=Karl R. |title=Control of binocular gaze in a high-precision manual task |journal=Vision Research |volume=110 |issue=Pt B |pages=203–214 |doi=10.1016/j.visres.2014.09.005|pmid=25250983 |year=2015 |doi-access=free }} and attentional shifts.{{cite journal |last1=Laubrock |last2=Engbert |last3=Kliegl |title=Microsaccade dynamics during covert attention |journal=Vision Research |volume=45 |issue=6 |pages=721–730 |doi=10.1016/j.visres.2004.09.029|pmid=15639499 |year=2005 |doi-access=free }}

Microsaccades play a crucial role in the perception of objects. Researchers discovered that these motions improve our ability to catch minute details in a scene. Microsaccades help gain focus from Troxler fading.{{Cite web |last=Martinez-Conde |first=Susana |date=January 2013 |title=The impact of microsaccades on vision: Towards a unified theory of saccadic function |url=https://www.researchgate.net/publication/234161521_The_impact_of_microsaccades_on_vision_Towards_a_unified_theory_of_saccadic_function}} Swiss philosopher Troxler had fixated images which tend to fade away during normal vision in 1804. Troxler effect is the fixating one's gaze in the visual field. A static field that would slowly fade into a blur. Microssacades are significant since it prevents image blur.{{Cite web |last=Thomas |first=G |date=July 2017 |title=Troxler Effect |url=https://www.illusionsindex.org/i/troxler-effect}} The brain activity stimulated by microsaccades across the visual system can aid in determining the neural coding of visibility because microsaccades are essential for preserving visibility during fixation. The neuronal reactions to alterations in visual inputs brought on by microsaccadic retinal displacements are known as visual responses to microsaccades.

Microsaccades are generated through neural activity in the brain regions responsible for eye movement control. The superior colliculus plays an important role in initiating microsaccades.{{Cite journal |last=Gandhi |first=Neeraj J. |last2=Katnani |first2=Husam A. |date=2011-07-21 |title=Motor Functions of the Superior Colliculus |url=https://www.annualreviews.org/doi/10.1146/annurev-neuro-061010-113728 |journal=Annual Review of Neuroscience |language=en |volume=34 |issue=1 |pages=205–231 |doi=10.1146/annurev-neuro-061010-113728 |issn=0147-006X|pmc=3641825 }} Neural circuits within the superior colliculus integrate sensory inputs and motor commands, resulting in the precise, coordinated movements of microsaccades.{{Cite journal |last=Yotsumoto |first=Yuko |last2=Chang |first2=Li-hung |last3=Watanabe |first3=Takeo |last4=Sasaki |first4=Yuka |date=2009 |title=Interference and feature specificity in visual perceptual learning |url=https://linkinghub.elsevier.com/retrieve/pii/S004269890900354X |journal=Vision Research |language=en |volume=49 |issue=21 |pages=2611–2623 |doi=10.1016/j.visres.2009.08.001 |pmc=2764795 |pmid=19665036}}

This process involves excitatory and inhibitory interactions between neurons in different layers of the superior colliculus. Inputs from cortical areas such as the frontal eye fields and parietal cortex modulate these interactions, influencing microsaccade frequency and direction.{{Cite journal |last=Krauzlis |first=Richard J. |last2=Lovejoy |first2=Lee P. |last3=Zénon |first3=Alexandre |date=2013-07-08 |title=Superior colliculus and visual spatial attention |url=https://pubmed.ncbi.nlm.nih.gov/23682659/ |journal=Annual Review of Neuroscience |volume=36 |pages=165–182 |doi=10.1146/annurev-neuro-062012-170249 |issn=1545-4126 |pmc=3820016 |pmid=23682659}} Experiments in primates have shown that electrically stimulating specific regions of the superior colliculus can evoke microsaccade-like movements, highlighting its role in their generation.{{Cite journal |last=Hafed |first=Ziad M. |last2=Goffart |first2=Laurent |last3=Krauzlis |first3=Richard J. |date=2008-08-06 |title=Superior Colliculus Inactivation Causes Stable Offsets in Eye Position during Tracking |url=https://www.jneurosci.org/lookup/doi/10.1523/JNEUROSCI.1317-08.2008 |journal=The Journal of Neuroscience |language=en |volume=28 |issue=32 |pages=8124–8137 |doi=10.1523/JNEUROSCI.1317-08.2008 |issn=0270-6474 |pmc=2553276 |pmid=18685037}}

In addition to the superior colliculus, subcortical structures like the basal ganglia may regulate the initiation or suppression of microsaccades. The basal ganglia's influence on fixation and spontaneous eye movements patterns suggest a contribution to attention shifts and stabilization during visual fixation.{{Cite journal |last=Beylergil |first=Sinem Balta |last2=Murray |first2=Jordan |last3=Noecker |first3=Angela M. |last4=Gupta |first4=Palak |last5=Kilbane |first5=Camilla |last6=McIntyre |first6=Cameron C. |last7=Ghasia |first7=Fatema F. |last8=Shaikh |first8=Aasef G. |date=2022 |title=Temporal Patterns of Spontaneous Fixational Eye Movements: The Influence of Basal Ganglia |url=https://journals.lww.com/10.1097/WNO.0000000000001452 |journal=Journal of Neuro-Ophthalmology |language=en |volume=42 |issue=1 |pages=45–55 |doi=10.1097/WNO.0000000000001452 |issn=1070-8022|url-access=subscription }}

Microsaccades are disrupted in various neurological disorders, including ADHD, schizophrenia, and Parkinson's disease, resulting in gaze instability during fixation. In ADHD, individuals show increased microsaccade rates and unstable gaze, which may improve with medication. In schizophrenia, microsaccades reveal similar total eye movement counts to healthy controls despite differences in large saccades. Parkinson's disease is associated with larger, more frequent, and slower microsaccades.

Microsaccades are disrupted in several ophthalmologic disorders, including amblyopia, strabismus, myopia, and macular disease, reflecting the impact of visual impairment on eye movement control. In amblyopia, monocular fixation with the amblyopic eye leads to increased drift and frequent saccadic intrusions, especially in cases involving strabismus. Myopia is associated with larger microsaccades as uncorrected refractive error worsens, linking blurred vision to fixational instability. Along with this, macular disease results in increased drift and larger microsaccadic amplitudes, which correlate with visual acuity loss and serve as signs of fixation instability.{{cite journal |last1=Alexander |first1=Robert |last2=Macknik |first2=Stephen |last3=Martinez-Conde |first3=Susana |title=Microsaccade Characteristics in Neurological and Ophthalmic Disease. |journal=Frontiers in Neurology |date=2018 |volume=9 |issue=144 |pages=144 |doi=10.3389/fneur.2018.00144|pmid=29593642 |pmc=5859063 |doi-access=free }}

• Fixation (visual)
• Ocular tremor
• Saccade

{{reflist|colwidth=40em}}{{Cite journal |last=Hafed |first=Ziad M. |last2=Krauzlis |first2=Richard J. |date=2012-04-01 |title=Similarity of superior colliculus involvement in microsaccade and saccade generation |url=https://www.physiology.org/doi/10.1152/jn.01125.2011 |journal=Journal of Neurophysiology |language=en |volume=107 |issue=7 |pages=1904–1916 |doi=10.1152/jn.01125.2011 |issn=0022-3077 |pmc=3331665 |pmid=22236714}}

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• R. H. S. Carpenter. Movements of the Eyes (Pion, London, 1988).
• Guerrasio, Lorenzo (2011). [http://edoc.ub.uni-muenchen.de/13441/1/guerrasio_lorenzo.pdf Subcortical Control of Visual Fixation.] Dissertation, LMU München: Faculty of Medicine.
• {{cite journal |doi=10.1038/nrn1348 |title=The role of fixational eye movements in visual perception |year=2004 |last1=Martinez-Conde |first1=Susana |last2=MacKnik |first2=Stephen L. |last3=Hubel |first3=David H. |journal=Nature Reviews Neuroscience |volume=5 |issue=3 |pages=229–40 |pmid=14976522|s2cid=27188405 }}

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Category:Eye

Category:Vision