Associative learning and stimulus novelty influence the song-induced expression of an immediate early gene in the canary forebrain.

To identify variables that affect immediate early gene (IEG) expression in the auditory telencephalon of songbirds, we developed a conditioning paradigm that trained adult male canaries to associate song with a mild shock. Learning of the association was measured by a bird's fear and avoidance responses. Birds exposed to paired song and shock were compared to yoked controls exposed to each stimulus alone or to both unpaired. Additional groups examined the effects of attention and stress, and of the novelty of the stimulus situation. In situ hybridization analysis of brain sections revealed an enhancement of ZENK expression in birds learning the association between song and shock above levels induced by song alone or yoked-unpaired song and shock. This effect was specifically seen in the caudomedial auditory telencephalon (NCM-HVCM). A comparison of the several control groups indicated that novelty of the song stimulus or of its pairing with shock were the main variables that predicted ZENK levels in NCM-HVCM. These observations are compatible with ZENK playing a role in the formation of song perceptual memories.