Saccadic “adaptation” at late target reappearance
Résumé
When the oculomotor system faces a discrepancy between the saccade endpoint and the visual target, it can attribute this discrepancy to a change in the environment or to a visual saccadic error. In the laboratory, a progressive adjustment in saccade amplitude is observed in the
presence of a systematic displacement of the target during the saccade. According to literature, saccadic adaptation is disrupted when the target is shortly blanked after the saccade, and disappears around a 600ms-blank. Because an increased blank leads to the perception of
target displacements, saccade amplitude modifications are thought to be negligible. We however believe that in the presence of a ystematically varying environment, we are still likely to adjust our saccadic amplitudes, but that the nature of this adjustment should differ. We examined, in a double-step adaptation paradigm, the effect of various temporal delays in the presentation of the post-saccadic target on the amount of saccadic adaptation. We hypothesize that an automatic and slow modification of saccadic amplitude (implicit learning) should take place for intrassacadic target displacements, whereas a more explicit learning (voluntary and fast) should dominate when target reappearance is delayed. Preliminary results show that saccades’ amplitude is modified up to a 1200ms delay (gain change: M=-14%, SD=10%), and still visible in large proportion up to 600ms (M=-20%, SD=8.9%). Our visual system seems to “adapt” eye movements even when target displacements can be attributed to a change in the environment and not to saccadic errors anymore. Interestingly, we observed an increase in saccadic endpoint variability (entropy, exploration) and saccades’ latency during adaptation, associated with a smaller amount of saccadic adaptation, when target reappearance was delayed and its displacement perceived. Our results indicate that adaptation profiles likely depend on how participants experienced their saccade landing errors
Domaines
Sciences cognitives
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