Administration of glutamate following a reminder induces transient memory loss in day-old chicks

Monosodium glutamate (4.0 mM) administered immediately after a visual reminder presented to day-old chickens between 7.5 min and 24 h following a single trial passive avoidance learning task produced transient losses of memory on retention test, an effect not observed in the absence of a reminder or when the reminder was given 48 h post-learning. The duration of the transient deficit decreased with increasing interval between the training and the reminder trial. The time of onset of memory loss after the reminder trial appeared to increase with increasing interval between the training and the reminder trials. The results suggest that, for a period of at least up to 24 h after passive avoidance training, retrieval of memory may lead to processes which are sensitive to inhibition by glutamate, with the duration of sensitivity post-retrieval decreasing as the period of memory consolidation increases. The results extend previously reported findings with rodents and suggest the possibility that consolidation of a stable memorial representation of a learning experience may take place over several days and may entail the concurrent laying down of a stable retrieval mechanism.