Taste responsivity of amygdaloid units in behaving rabbit: a methodological report

A technique is described for studying unit electrophysiology of taste in the behaving animal. Preliminary observations on response patterns by amygdaloid units to four putative basic types of taste qualities (represented by sucrose, saline, acid, and quinine), which also vary in motivational properties, revealed evidence of units with exclusive or highly differential response to either sucrose or saline in food-deprived animals. Small quantities (0.3 ml) of these palatable tastants injected intra-orally evoked neural responses lasting 5-8 sec that did not relate directly to the characteristics of the oro-lingual reaction as detected electromyographically; such sensorimotor relations were found in units sampled in the globus pallidus. Some amygdaloid units displayed differential excitatory and inhibitory modes of response to different tastants. Other cells exhibited more phasic patterns of response lasting 1-2 sec to 2 or more tastants, including unpalatable acid and quinine. The results underscore the sensitivity of the technique to stimulus parameters of taste-processing, which is basic to the study of all neurobehavioral functions of taste stimuli.