July 2013
Volume 13, Issue 9
Free
Vision Sciences Society Annual Meeting Abstract  |   July 2013
Adaptation of micro-saccades reveals active control during fixation
Author Affiliations
  • Katharina Havermann
    Institute for Psychology, University of Muenster, Germany\nOtto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Muenster, Germany
  • Claudia Cherici
    Departments of Psychology and Program in Neuroscience, Boston University, Boston, USA
  • Michele Rucci
    Departments of Psychology and Program in Neuroscience, Boston University, Boston, USA
  • Markus Lappe
    Institute for Psychology, University of Muenster, Germany\nOtto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Muenster, Germany
Journal of Vision July 2013, Vol.13, 110. doi:10.1167/13.9.110
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    • Get Citation

      Katharina Havermann, Claudia Cherici, Michele Rucci, Markus Lappe; Adaptation of micro-saccades reveals active control during fixation. Journal of Vision 2013;13(9):110. doi: 10.1167/13.9.110.

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

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Abstract

When asked to maintain their gaze steady on a given location, humans perform small involuntary eye movements, which include drifts and fixational saccades. It has long been speculated that fixational saccades may contribute to the maintenance of fixation, but direct evidence that these movements are under oculomotor control has remained contradictory. Here we show that these fixational saccades are indeed precisely monitored and controlled. We used saccadic adaptation, an experimental procedure in which the stimulus is shifted during saccades, to expose observers to an altered sensory-motor contingency. We first examined whether target-directed saccades with amplitudes within the microsaccade range (30 arcmin) could be adapted. Subjects were instructed to look at a small dot (3'), which shifted by a fixed amount every time the subject made a saccade toward the target. Repeated exposure to this procedure led to changes (both shortening and lengthening, depending on the intra-saccadic shift direction) in microsaccade amplitude. We then examined whether fixational saccades, the microsaccades that occur during fixation of a stationary marker, are also adaptable. Since the occurrence of fixational saccades is unpredictable, we estimated the direction and amplitude of a fixational saccade during its occurrence and shifted the fixation dot proportionally. Fixational saccades also changed during prolonged exposure to this procedure: the average amplitude of fixational saccades decreased following backward shifts of the fixation marker and increased following forward shifts. These findings show that the success of fixational saccades is linked to the post-saccadic position of the fixation point, so that the motor program of fixational saccades is modified if the fixation point is not at the expected retinal location after the saccade. Thus fixational saccades serve to position the eye with respect to the fixation point and are actively controlled at a minute level of detail.

Meeting abstract presented at VSS 2013

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