Odor coding in the Drosophila antenna

Odor coding in the Drosophila antenna is examined by a functional analysis of individual olfactory receptor neurons (ORNs) in vivo. Sixteen distinct c lasses of ORNs, each with a unique response spectrum to a panel of 47 diver se odors, are identified by extracellular recordings. ORNs exhibit multiple modes of response dynamics: an individual neuron can show either excitator y or inhibitory responses, and can exhibit different modes of termination k inetics, when stimulated with different odors. The 16 ORN classes are combi ned in stereotyped configurations within seven functional types of basiconi c sensilla. One sensillum type contains four ORNs and the others contain tw o neurons, combined according to a strict pairing rule. We provide a functi onal map of ORNs, showing that each ORN class is restricted to a particular spatial domain on the antennal surface.