Rapid induction of the immediate early gene c-fos in a chick forebrain system involved in memory.

Previous work has shown that expression of Fos protein in neurons of the intermediate and medial mesopallium (IMM), a memory region in the forebrain of the domestic chick, increases in a learning-related manner after behavioural imprinting. We show here, using in situ hybridisation, that when chicks are trained for 15 min with an imprinting stimulus, expression of c-fos mRNA in the IMM rises to a maximum at or before the end of this training period. The results suggest that the learning-related increase in Fos protein production, which occurs in identifiable neuronal sub-populations in the IMM, reflects events that make an early contribution to learning and/or memory processing.