Adaptation of Reactive Saccades in Normal Children

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To compare the amount, the retention, and the extinction of saccadic adaptation in two groups: 9 adults (23-36 years old) and 9 children (11-14 years old). The paradigm used was a classical double-step target to elicit the shortening of saccade gains in response to a 2° backward step (20% of target eccentricity). Two conditions were run in the pre- and postadaptation phases without and with postsaccadic visual feedback, to allow examination of the retention and the extinction of saccadic adaptation. Adaptation of reactive saccades occurred in children as well as adults. Both groups showed a progressive shortening of saccade amplitude and good retention. The main difference concerned the speed of extinction, i.e., return to baseline, which was slower for children. Cerebral structures involved in human short-term adaptation of reactive saccades are functional in regard to adaptive shortening of saccade amplitude. Divergent patterns in the extinction of adaptation between children and adults suggested that lengthening of saccade gain is not yet well established in children. Further investigation is needed to clarify whether processes responsible for backward adaptation are mature before those for forward adaptation.