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Rana Arham Raashid, Herbert Goltz, Alan Blakeman, Agnes Wong; Gain-increase saccadic adaptation is enhanced by the use of constant retinal error feedback. Journal of Vision 2016;16(12):849. doi: 10.1167/16.12.849.
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© 2017 Association for Research in Vision and Ophthalmology.
Introduction: Saccadic accuracy is maintained by sensorimotor adaptive mechanisms that continually adjust movement gains when faced with consistent errors. It is known that generally the saccadic system is resistant to increasing its gain. This study investigates whether gain-increase saccadic adaptation can be improved by using a constant "retinal error" (RE) instead of the conventional "spatial error" (SE). Because adaptation is driven by the dynamic comparison of actual and predicted postsaccadic errors, we hypothesized that there would be an increased saccadic gain change in the RE compared to the SE condition. Methods: Eleven visually-normal observers performed two experimental sessions. Each session included three blocks: preadaptation, adaptation, and postadaptation during binocular viewing. In the control SE condition, the target appeared at ±10° followed by a 3° step in the same direction during the primary saccade. In the RE condition, the second step always appeared 3° away from the trial-by-trial real-time eye position after the primary saccade. Eye movements were tracked with the EyeLink II at 250 Hz. Percentage saccadic gain change and percentage gain retention from baseline were calculated. Results: All participants but one increased their saccadic gains substantially. Mean percentage gain change was higher in the RE (58±22%) compared to the SE (38±13%; p=0.01) condition. Adaptation retention was augmented in the RE condition for six out of ten participants, however the mean percentage retention was not statistically significant between conditions (RE=36±15%, SE=27±19%; p=0.26). Conclusions: This study provides a novel comparison of the constant retinal error and the conventional spatial error in driving gain-increase saccadic adaptation. The greater adaptation magnitude during the RE condition corroborates previous findings that a consistent disparity between the actual and predicted error plays a major role in driving saccadic adaptation. We intend to implement this enhanced technique in the future to study gain-increase saccadic adaptation in amblyopia.
Meeting abstract presented at VSS 2016
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