The basis for the consolidation of memory is a controversial topic, particularly in the case of motor memory. One view is that motor memory is transferred, partially or completely, to a new location during the consolidation process ("systems consolidation"). We investigated this possibility in a primitive motor system, the vestibulo-ocular reflex (VOR). In the simple circuitry of the VOR, there are relatively few possible storage sites for memory. We partially blocked excitatory neurotransmission in the cerebellar cortex of cats with the glutamate antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). If CNQX was injected immediately after 60 min of rotation under conditions that induced a learned decrease in the gain of the VOR, gain was returned to its baseline value. Expression of the new memory could also be disrupted by rotation in darkness, suggesting that consolidation had not taken place; however, after learning had continued for 3 d, expression of the learned change was diminished only slightly by blockade and was unaffected by rotation in darkness. Our interpretation of these results is that learning may take place initially in the cerebellar cortex and that during consolidation, motor memories are converted to a more distributed representation that includes the cerebellar cortex and another site.

Motor memory is relatively labile immediately after learning but can become more stable through consolidation. We investigated consolidation of motor memory in the vestibuloocular reflex (VOR). Cats viewed the world through telescopic lenses during 60 min of passive rotation. Learned decreases (gain-down learning) and increases in the VOR gain (gain-up learning) were measured during sinusoidal rotation at 2 Hz. We found that if rotation in darkness immediately followed learning, the gain of the VOR reverted toward its prelearning value, indicating that expression of the memory was disrupted. If after gain-down learning the cat spent another 60 min stationary without form vision, subsequent disruption did not occur, suggesting that memory had consolidated. Consolidation was less robust for gain-up learning. We conclude that memory in the VOR is initially labile but consolidates rapidly and consistently after gain-down learning.