PRIOR EXPERIENCE SHAPES NEURAL RESPONSES TO LEARNED AND NOVEL STIMULI AFTER FILIAL IMPRINTING IN DOMESTIC CHICKS

Filial imprinting is an early learning process in which exposure to an object leads to a restricted social preference and is associated with a sensitive period. In domestic chicks, imprinting alters neural responsiveness in the intermediate and medial mesopallium (IMM) and depends on undisturbed sleep 5–12 h after exposure for consolidation. Here, we examined how prior experience influences neural activity in the IMM in response to re-exposure to a learned stimulus or exposure to a novel stimulus after consolidation. Dark-reared chicks (24 h old) were assigned to five groups differing in Day 1 and Day 2 visual experience, including re-exposure to a learned stimulus, exposure to a novel stimulus, or no visual exposure (dark indicates housing in complete darkness without visual stimulation). Visual stimuli were presented for 30 min, and expression of the immediate early genes c-fos and egr-1 in the IMM was examined 2 h after Day 2 exposure using immunocytochemistry. Fos-like immunoreactivity increased bilaterally in the IMM following imprinting, as observed after first exposure. Exposure to a novel stimulus after prior imprinting induced a significant increase in the right IMM, whereas re-exposure to the learned stimulus produced more moderate changes. These findings indicate that prior experience shapes neural activation patterns in the IMM and suggest differential processing of learned and novel stimuli following imprinting consolidation.This work was supported by JSPS KAKENHI Grant Number 19K03369 and 23K03016.