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Sohir Rahmouni, Laurent Madelain; Inter-individual variability in saccadic adaptation. Journal of Vision 2015;15(12):1281. doi: 10.1167/15.12.1281.
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© ARVO (1962-2015); The Authors (2016-present)
Saccadic adaptation reflects the oculomotor system ability to adapt in response to changes in sensorimotor contingencies. This may be observed in the laboratory using a double step paradigm (McLaughlin, 1967). Adaptation of saccadic amplitude or direction is triggered by the intrasaccadic target displacement that introduces a postsaccadic position error. Numerous studies explored this form of oculomotor learning revealing the reproductibility of this phenomenon. However, large interindividual variability in the amount of saccade gain change is often observed to the extent that a fraction of subjects do not adapt at all. Previous studies did not systematically describe saccade adaptation variability. Moreover, current theories of motor adaptation do not account for these idiosyncratic effects. To provide a detailed description of variations in adaptation, we conducted experiments in a large number (currently 42) of naïve participants. We used a double step paradigm in which a small disc target jumped away from fixation position (amplitude ranging from 7.5 to 14 deg) with a 45 deg angle with respect to the horizontal. The target was displaced during the saccade, and this second step was either purely horizontal (Backward or Forward) or vertical (Upward or Downward) in four different experiments such that only the horizontal or vertical saccade component would adapt. We found a large dispersion in percent gain changes (ratio of change in gain during adaptation by baseline gain - in the horizontal or vertical component depending on the intrasaccadic step) : Backward adaptation [-21%; -4%], p< 0.01 in 9/10 subjects; Forward [+11%; +26%], 13/13 subjects; Upward [-3%; +18%], 4/9 subjects; Downward [-33%; -11%], 10/10. To evaluate the effects of individual oculomotor control on saccade adaptation we also ask, for each subject, whether the amount of adaptation correlates with various saccade parameters such as amplitude in baseline trials, saccade latency or saccade peak velocity.
Meeting abstract presented at VSS 2015
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