MECHANISMS OF OLFACTORY DISCRIMINATION - CONVERGING EVIDENCE FOR COMMON PRINCIPLES ACROSS PHYLA

Olfaction begins with the transduction of the information carried by o dor molecules into electrical signals in sensory neurons. The activati on of different subsets of sensory neurons to different degrees is the basis for neural encoding and further processing of the odor informat ion by higher centers in the olfactory pathway. Recent evidence has co nverged on a set of transduction mechanisms, involving G-protein-coupl ed second-messenger systems, and neural processing mechanisms, involvi ng modules called glomeruli, that appear to be adapted for the require ments of different species. The evidence is highlighted in this review by focusing on studies in selected vertebrates and in insects and cru staceans among invertebrates. The findings support the hypothesis that olfactory transduction and neural processing in the peripheral olfact ory pathway involve basic mechanisms that are universal across most sp ecies in most phyla.