Thalamic taste responses to changing stimulus concentration

In the rat brainstem, where responses are often vigorous tobasic gustatory stimuli, the code for taste intensity appearsto be a function of total neural activity. By contrast, thalamicneurons respond sluggishly to stimuli representing the fourbasic taste qualities, and total neural activity does not risesignificantly with increasing stimulus concentration. Rather,most thalamic cells (61%) show sensitivity to concentrationchanges of one or more qualities, but a distinct minority areunaffected by intensity. Further, increases in stimulus concentrationmay affect the neurons which are sensitive either directly orinversely. Thus, only a subpopulation of thalamic neurons seemsto signal stimulus intensity, doing so through both excitatoryand inhibitory responses. The role of the thalamus in processingtaste information is discussed.