Novel object recognition in the dorsomedial and ventral hippocampus of young domestic chicks (Gallus gallus)

The avian hippocampus is well known for its role in spatial cognition, but its contribution to non-spatial domains such as novelty detection remains poorly understood. Here, we examined whether the ventral hippocampus in domestic chicks (Gallus gallus) is involved in processing non-spatial novelty. On post-hatching day 5, chicks were exposed to either a novel or a familiar object. Chicks of both sexes recognised the novel object, showing delayed approach, greater distance from the object, and increased locomotion, consistent with neophobic behaviour. Neural activation was mapped using c-Fos immunohistochemistry in the hippocampus, septum, nucleus taeniae of the amygdala (TnA), and intermediate medial mesopallium (IMM). Exposure to novelty selectively increased c-Fos expression in the dorsomedial and ventral hippocampus, independent of hemisphere, while no differences were observed in the septum, TnA, or IMM. This hippocampal activation was significant in males and showed a non-significant trend in females. These findings suggest that the dorsomedial and ventral hippocampus contribute to detecting and evaluating novel stimuli beyond spatial contexts, at least in males, supporting its involvement in novelty-related learning. Together with previous evidence from spatial and social paradigms, these results point to a domain-general role of the avian ventral hippocampus in processing novelty.