The main olfactory system and social learning in mammals.

There is increasing evidence for specialised processing of social cues in the brain. This review considers how the main olfactory system of mammals is designed to process social odours and the effects of learning in a social context. It focuses mainly on extensive research carried out on offspring, mate or conspecific learning carried out in sheep and rodents. Detailing the roles of the olfactory bulb and its projections, classical neurotransmitters, nitric oxide, oestrogen and neuropeptides such as oxytocin and vasopressin in mediating plasticity changes in the olfactory system arising from these different social learning contexts. The relative simplicity of the organisation of the olfactory system, the speed and robustness of these forms of social learning together with the similarity in brain regions and neurochemical contributions across the different learning paradigms make them important and useful models for investigating general principles of learning and memory in the brain.