Experimental analysis of the processes of systems genesis: expression of the c-fos gene in the chick brain during treatments inducing the development of the species-specific results-of-action acceptor.

The aim of the present work was to identify which parts of the chick brain are activated during treatments inducing the development of the preference to follow a species-specific object (a stuffed chick). Expression of the gene for the transcription factor c-fos was used as the molecular marker for neuron activation. Day-old chicks lacking visual experience were placed for 90 min in a freely rotating squirrel wheel or were subjected to stimulation with a loud noise for 180 min. The animals' preference was tested 24 h after stimulation ended. Both types of stimulation induced the formation of a marked preference to follow the "natural" object in the chicks. c-fos expression was analyzed in sections from the brains of chicks stimulated for 45 min. Increases in the quantity of c-fos mRNA were seen after each type of stimulation in the medial part of the caudal neostriatum. In addition, stimulation in the squirrel wheel was accompanied by high levels of c-fos expression in the paraolfactory lobes, while sound stimulation gave high levels of c-fos expression in the ventral and caudal parts of the archistriatum. These structures of the chick brain are of great interest for studies of the cellular and molecular mechanisms of the formation of the species-specific results-of-action acceptor in the mother-following functional system.