c‑Fos Expression Reveals Activation of the Thalamofugal System in the Categorization Learning Model in Chicks.

The expression of the transcription factor c‑Fos was mapped in the brains of newborn chicks during visual categorization training. It was found that this learning was accompanied by a significant increase in c‑Fos levels in the hippocampus and striatum, as well as in the pallial structures of the thalamofugal visual pathway and in areas integrating visual information. At the same time, no induction of c‑Fos expression was observed in the pallial portion of the tectofugal visual pathway, which is often considered to be involved in categorization learning. The obtained data expand current understanding of the contribution of parallel visual systems in the avian brain to learning processes.