Memory reactivation, dissociated from behavioural expression, decreases ERK phosphorylation in the rat prefrontal cortex and amygdala.

The involvement of MAPK pathways in retrieval was investigated in a situation where reactivation of memory was dissociated from its behavioural expression. In rats trained in a brightness avoidance discrimination task, exposure to the discriminative stimulus had behavioural and molecular consequences: a facilitation of the retention performance and a decrease in ERK phosphorylation in the prefrontal cortex and amygdala, but not in the hippocampus. These results indicate that reactivation processes engage a down-regulation of ERK, possibly related to increases in glucocorticoids, in the amygdala and prefrontal cortex already known to be involved in emotional retrieval.