Representation of environmental shape in the hippocampus of domestic chicks (Gallus gallus).

The hippocampus plays an important role in spatial encoding and memory across various vertebrate species. In rodents, hippocampal neurons are particularly sensitive to a change in environmental geometry. Given the similarities in function between the mammalian and avian hippocampi, we aimed to measure whether enclosures varying in geometric shape (square and rectangle) can differentially activate hippocampal cells in the domestic chick (Gallus gallus domesticus). Chicks exposed to both a square and a rectangular arena exhibited a significantly higher neural activation (as measured by c-Fos expression) than those exposed twice to just the square or just the rectangle (both of which were significantly higher in activation than a one-environment control group). For the first time in an avian species, we show that exposure to two enclosures of different geometric shape activates the hippocampus to a greater degree, suggesting a possible effect of spatial remapping.