The Latency of Pathways Containing the Site of Motor Learning in the Monkey Vestibulo-Ocular Reflex

The vestibulo-ocular reflex helps to stabilize retinal images by generating smooth eye movements that are equal to and opposite each rotatory head movement. It is well known that the reflex undergoes adaptive plasticity or ``motor learning'' whenever there is persistent image motion during head turns: the resulting changes in the reflex occur gradually and help to restore image stability. A new approach makes it possible to identify the pathways containing the site of motor learning according to their total latency in response to natural vestibular stimuli. The fastest pathways required 14 milliseconds to initiate a vestibulo-ocular reflex, but the site of motor learning was in pathways having latencies of at least 19 milliseconds.