Brainstem correlates of gustatory similarity in the hamster

Responses of neurons in the nucleus tractus solitarius (NTS) and parabrachial pons (Pb pons) of the hamster to 10 gustatory stimuli were compared to behavioral similarities among these compounds. Animals were given a conditioned taste aversion to one of the 10 stimuli by pairing it with an induced gastrointestinal illness. Following this procedure, the degree of generalization of the learned taste aversion to each of the other compounds was measured. Behavioral similarity profiles were derived for each stimulus from the similarities in the generalization profiles of each pair of compounds. The across-neuron correlations in the firing rates evoked by these stimuli in the NTS cells corresponded quite well to these behavioral profiles, as did these neural correlations among Pb pontine cells, except for those correlations involving quinine. Sucrose-best cells in the Pb pons are too broadly responsive to account for the behavioral similarity functions for sweet-tasting stimuli, although other best-stimulus categories of cells (NaCl- and HCl-best) showed response profiles quite similar to the behavioral profiles, as did all best-stimulus classes of cells in the NTS.