Hemispheric lateralization of memory stages for discriminated avoidance learning in the chick

Memory formation following the one trial discriminated bead task in the chick falls into three stages (short-term, intermediate and long-term memory) that are defined by susceptibility to different classes of drugs. The stages show sharply timed offsets of sensitivity and loss at specific times after inhibition. Recall of the memory in the chick shows cyclical changes that differ in period between left and right hemispheres, and is marked by a series of brief windows of enhanced recall that recur with periods of about 16 and 25 min in the left and right hemispheres respectively. The timing of these 'retrieval events' corresponds, to a large extent, with the timing of the memory stages seen in the visual discrimination task. Here we examine the effects of left or right hemisphere injection of the main agents (glutamate, ouabain and anisomycin) that have been used to characterize the three stages of memory. We show that memory in the left hemisphere is largely responsible for performance at test and that processes involved in its consolidation generate the phases of memory.