Enhancement of spatial learning by predator odor in mice: involvement of amygdala and hippocampus

Olfaction has particular links with learning and memory compared with other sensory cues, due to the interrelations between their neural circuitry. The present study deals with the effects of a putative stressor (i.e. a predator odor) on visuo-spatial learning in mice. Firstly, the results show that a predator odor spread during the Morris water maze task led to learning enhancement. In addition, a stereotaxic approach was used to investigate the involvement of the amygdala in this hippocampus-dependent type of learning. Thus, the performance of mice in visuo-spatial learning under predator odor conditions was dramatically reduced by an ibotenate bilateral amygdala lesion. The involvement of the amygdala was confirmed by a reduced expression of c-fos in the CA1 hippocampus of amygdala-lesioned mice at the end of the learning procedure. Mild exposure to a predator odor during hippocampus-dependent learning therefore leads to an enhancement of performance through the co-activation of the amygdala, probably by a stress mediated mechanism.