Microsaccade

Microsaccades are a kind of fixational eye movement. They are small, jerk-like, involuntary eye movements, similar to miniature versions of voluntary saccades. They typically occur during prolonged visual fixation (of at least several seconds), not only in humans, but also in animals with foveal vision (primates, cats, dogs etc.). Microsaccade amplitudes vary from 2 to 120 arcminutes. The first empirical evidence for their existence was provided by Robert Darwin, the father of Charles Darwin.[1][2]

For other uses, see Eye movement.

Function

The role of microsaccades in visual perception has been a highly debated topic that is still largely unresolved. It has been proposed 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.[3][4][5] Although microsaccades can enhance vision of fine spatial detail,[6][7] they can also impair visual perception in that they are associated with saccadic suppression.[8] Microsaccades are also believed to be important for preventing the retinal image from fading.[9]

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.[10][11]

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.[12][13] 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,[14] control of binocular fixation disparity[15] and attentional shifts.[16]

Clinical application

The assessment of microsaccades can help in the diagnosis of multiple neurological and ophthalmological conditions.[17]

See also

References

Notes
  1. Darwin, R. W.; Darwin, E. (1786). "New Experiments on the Ocular Spectra of Light and Colours". Philosophical Transactions of the Royal Society of London. 76: 313–348. doi:10.1098/rstl.1786.0016. JSTOR 106628.
  2. Rolfs, Martin (2009). "Microsaccades: Small steps on a long way". Vision Research. 49 (20): 2415–41. doi:10.1016/j.visres.2009.08.010. PMID 19683016.
  3. "Optical illusions: caused by eye or brain?"
  4. 200-year-old Scientific Debate Involving Visual Illusions
  5. The truth behind 'Where's Waldo?'
  6. Rucci, M., Iovin, R., Poletti, M., Santini, F. (2007). "Miniature Eye Movements Enhance Fine Spatial Detail." Nature,447(7146), 851-854.
  7. "Eye flickers key for fine detail". BBC News. June 2007.
  8. Beeler, G. W. (1967). "Visual threshold changes resulting from spontaneous saccadic eye movements". Vision Research. 7 (9): 769–75. doi:10.1016/0042-6989(67)90039-9. PMID 5608665.
  9. Alexander, R. G.; Martinez-Conde, S (2019). "Fixational eye movements". Eye Movement Research. Springer, Cham. pp. 73–115.
  10. Yablonski, M; Polat, U; Bonneh, YS; Ben-Shachar, M (21 June 2017). "Microsaccades are sensitive to word structure: A novel approach to study language processing". Scientific Reports. 7 (1): 3999. Bibcode:2017NatSR...7.3999Y. doi:10.1038/s41598-017-04391-4. PMC 5479819. PMID 28638094.
  11. Krauzlis, Richard J. (2013). "Eye Movements". Fundamental Neuroscience (4 ed.). Academic Press. pp. 697–714. doi:10.1016/B978-0-12-385870-2.00032-9. ISBN 9780123858702.
  12. Rucci, Michele; Edelman, Gerald M.; Wray, Jonathan (2000). "Modeling LGN responses during free-viewing: A possible role of microscopic eye movements in the refinement of cortical orientation selectivity". Journal of Neuroscience. 20 (12): 4708–4720. doi:10.1523/JNEUROSCI.20-12-04708.2000. PMC 6772442. PMID 10844040.
  13. Leopold, D. A.; Logothetis, N. K. (1998). "Microsaccades differentially modulate neural activity in the striate and extrastriate visual cortex". Experimental Brain Research. 123 (3): 341–5. doi:10.1007/s002210050577. PMID 9860273. S2CID 18751039.
  14. Martinez-Conde, S; Alexander, R (2019). "A gaze bias in the mind's eye". Nature Human Behaviour. 3 (5): 424–425. doi:10.1038/s41562-019-0546-1. PMID 31089295. S2CID 71148025.
  15. Valsecchi, Matteo; Gegenfurtner, Karl R. (2015). "Control of binocular gaze in a high-precision manual task". Vision Research. 110 (Pt B): 203–214. doi:10.1016/j.visres.2014.09.005. PMID 25250983.
  16. Laubrock; Engbert; Kliegl (2005). "Microsaccade dynamics during covert attention". Vision Research. 45 (6): 721–730. doi:10.1016/j.visres.2004.09.029. PMID 15639499.
  17. Alexander, Robert; Macknik, Stephen; Martinez-Conde, Susana (2018). "Microsaccade Characteristics in Neurological and Ophthalmic Disease". Frontiers in Neurology. 9 (144): 144. doi:10.3389/fneur.2018.00144. PMC 5859063. PMID 29593642.

Bibliography
  • R. H. S. Carpenter. Movements of the Eyes (Pion, London, 1988).
  • Guerrasio, Lorenzo (2011). Subcortical Control of Visual Fixation. Dissertation, LMU München: Faculty of Medicine.
  • Martinez-Conde, Susana; MacKnik, Stephen L.; Hubel, David H. (2004). "The role of fixational eye movements in visual perception". Nature Reviews Neuroscience. 5 (3): 229–40. doi:10.1038/nrn1348. PMID 14976522. S2CID 27188405.
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