• A L Mueller, A J Davis, and F R Robinson.
• Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Box 357420, Seattle, WA 98195, United States. alm04@uw.edu
• Neuroscience. 2012 Nov 8;224:38-47.

AbstractMotor learning adjusts movement size and direction to keep movements accurate. A useful model of motor learning, saccade adaptation, uses intra-saccade target movement to make saccades seem inaccurate and elicit adaptive changes in saccades. In the most studied saccade adaptation procedure, which we call short-term saccade adaptation (STSA), monkeys decrease or increase the size of their saccades by tracking 1000-2000 adapting target movements in a single saccade session. STSA elicits rapid changes of limited size and duration. Larger, more persistent reduction in saccade size results from adapting saccades daily for 19 days, a procedure that we call long-term saccade adaptation (LTSA). LTSA mimics the demands of rehabilitation more closely than does STSA and, unlike STSA, produces changes that could maintain long-term accuracy. Previous work describes LTSA that reduces saccade size in monkeys. Though convenient to study, size-decreasing LTSA is not a good model for rehabilitation because few injuries necessitate making movements smaller. Here we characterize size-increasing LTSA and compare it, in the same monkeys, to size-reducing LTSA. We found that size-increasing LTSA can double saccade gain in ∼21 days, and is slower than size-decreasing LTSA. In contrast to a single size-decreasing STSA, a single size-increasing STSA does not prevent additional saccade size increase at the normal rate when a monkey continues to track adapting target movements. We conclude that size-increasing LTSA is slower than size-decreasing LTSA but can make larger changes in saccade size. Size-increasing and size-decreasing LTSA use distinct mechanisms with different performance characteristics.Copyright © 2012 IBRO. Published by Elsevier Ltd. All rights reserved.

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