Neural Codes for the Sense of Taste

Four of the five major sensory systems (vision, olfaction, somatosensation, and audition) are thought to use different but partially overlapping sets of neurons to form unique representations of vast numbers of stimuli. Gustation is considered an exception, by representing only small numbers of basic taste categories. Using new methods for delivering tastant chemicals and making electrophysiological recordings from the gustatory system of the moth Manduca sexta, we found that chemical-specific information is initially encoded in the population of gustatory receptor neurons as broadly distributed spatiotemporal patterns of activity, dramatically integrated and temporally transformed as it propagates to monosynaptically connected second-order neurons, and observed in tastant-specific behavior. Our results suggest that the gustatory system, rather than constructing basic taste categories, uses a spatiotemporal population code to generate unique neural representations of individual tastant chemicals.