Active exploration of a novel environment drives the activation of the hippocampus-amygdala complex of domestic chicks.

In birds, like in mammals, the hippocampus critically mediates spatial navigation through the formation of a spatial map. This study investigates the impact of active exploration of a novel environment on the hippocampus of young domestic chicks, during formation of a new spatial map. Chicks that were free to actively explore the novel environment exhibited a significantly higher neural activation (measured by c-Fos expression), compared to those that passively observed the novel environment from a restricted area. The difference was limited to the anterior and the dorsolateral parts of the intermediate hippocampus. Furthermore, the nucleus taeniae of the amygdala showed a higher c-Fos expression in the active exploration group than the passive observation group. In both brain regions, brain activation correlated with the number of locations that chicks visited during the test. This suggest that the increase of c-Fos expression in the hippocampus is related to increased firing rates of spatially coding neurons. Furthermore, our study indicates a functional linkage of the hippocampus and nucleus taeniae of the amygdala in processing spatial information. Overall, with the present study, we confirm that, in birds like in mammals, exploration of novel environments activates hippocampus, which is likely related to the formation of new spatial representations. Summary statementActive exploration of a novel environment induces stronger activation of hippocampus and taeniae of domestic chicks than pure visual, passive exploration from a restricted area.