August 2014
Volume 14, Issue 10
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2014
Spatial Distribution of Slow Involuntary Fixational Eye Movements is Related to the Occurrence of Microsaccades and Their Shapes
Author Affiliations
  • Debashis Sen
    School of Computing, National University of Singapore
  • Chengyao Shen
    Department of Electrical and Computer Engineering, National University of Singapore
  • Mohan Kankanhalli
    School of Computing, National University of Singapore
  • Zhi Yang
    Department of Electrical and Computer Engineering, National University of Singapore
  • Qi Zhao
    Department of Electrical and Computer Engineering, National University of Singapore
Journal of Vision August 2014, Vol.14, 111. doi:10.1167/14.10.111
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      Debashis Sen, Chengyao Shen, Mohan Kankanhalli, Zhi Yang, Qi Zhao; Spatial Distribution of Slow Involuntary Fixational Eye Movements is Related to the Occurrence of Microsaccades and Their Shapes. Journal of Vision 2014;14(10):111. doi: 10.1167/14.10.111.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

During fixations, involuntary miniature fixational eye movements (FEMs) are generated which include microsaccades (fast FEMs), drifts and tremors (slow FEMs), with the slow FEMs occurring between microsaccades. Here we examined the relationship between microsaccades and their temporally-neighboring slow FEMs. We first examined how the spatial distributions of the slow FEMs relate to the occurrence of microsaccades. Further, we investigated how they are related to the shapes of microsaccades. We define a microsaccade's shape as the ratio (R) of its path length to the spatial distance it covers, with a larger R indicating less linearity. In the experiment, subjects were instructed to fixate at a randomly positioned dot (0.26°) and press any key on its disappearance, during which an irrelevant cue (1°) appeared around the dot for two seconds. The cue contained luminance, equiluminant color, or luminance+color contrasts. From the FEMs during the cue onset, we measured variance of three types of sampled slow FEM cluster: (1) cluster of those preceding a microsaccade, (2) cluster of those when no microsaccade occurs, and (3) cluster of those preceding and succeeding a microsaccade combined together. We find that the variance of the cluster when no microsaccade occurs is statistically larger (p<.001) than that preceding a microsaccade, suggesting that the extent of spatial area covered by slow FEMs preceding a microsaccade is employed by the mechanism that generates microsaccades. Furthermore, for a microsaccade with a larger R (mostly nonlinear overshoot burst followed by returning movement), the variance of the cluster combining slow FEMs just before and after it, is statistically smaller (p<.001). Therefore, microsaccades with larger R are more likely to occur for fixation correction, as such an intention should lead to a smaller variance of the combined cluster. Microsaccades with smaller R occur most likely for other purposes, such as sampling.

Meeting abstract presented at VSS 2014

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