RT Journal Article
SR Electronic
T1 Memory of Learning Facilitates Saccadic Adaptation in the Monkey
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 7531
OP 7539
DO 10.1523/JNEUROSCI.1741-04.2004
VO 24
IS 34
A1 Kojima, Yoshiko
A1 Iwamoto, Yoshiki
A1 Yoshida, Kaoru
YR 2004
UL http://www.jneurosci.org/content/24/34/7531.abstract
AB A motor learning mechanism called saccadic adaptation ensures accuracy of saccades throughout life despite growth, aging, and some pathologies of the oculomotor plant or nervous system. The present study investigates effects of preceding adaptation on the speed of subsequent adaptation during single experiments. Adaptive changes in gain (movement size divided by target eccentricity) were induced by intrasaccadic step (ISS) of the target. After the gain was altered (control block), we reversed the direction of ISS to bring the gain back to ∼1.0 (recovery). We then reversed ISS direction again to induce another adaptation (test block). Analyses revealed that the gain changed at a higher rate in the early part of test adaptation than in the corresponding part of control. After ∼100-300 saccades in the test block, adaptation slowed down. The gain value at which adaptation slowed was correlated with the gain achieved in the control. We further examined effects of a 30 min intervention inserted between recovery and test blocks. When zero-visual-error trials (∼700 saccades) were repeated during this period, the rate of test adaptation was similar to that of control. In contrast, when the animal was deprived of visual inputs during this period, test adaptation was still influenced by preceding learning. We conclude that a memory of previous learning remains during recovery to facilitate subsequent adaptation and that such a memory does not disappear merely with time but is erased actively by repeated zero-error movements. Our results, which cannot be explained by a single mechanism, suggest that the saccadic system is equipped with more than one plasticity process.