Response characteristics of amygdaloid neurons provoked by emotionally significant environmental stimuli in cats, with special reference to response durations.

Abstract

Extracellular single or multiple neuronal activities were recorded from the basolateral portion of the amygdala of wild adult cats under an unanesthetized, freely moving condition, and neuronal responsiveness to neutral, aversive, and appetitive stimuli was studied. Of 71 units, 47 (66%) responded to some of the stimuli. The patterns of neuronal responses were classified into three types on the basis of response duration. Of the responses sampled, 9% rapidly attenuated and disappeared before termination of stimulus presentation (pattern A), 58% of responses were maintained during the period of the stimulus presentation but disappeared abruptly after termination (pattern B), and 33% of responses markedly outlasted the stimulus presentation period (pattern C). Pattern A responses habituated readily and were most prominent when neutral stimuli were presented, so this type of response was considered to underlie altering or orienting responses. Pattern B responses were observed equally for the three kinds of stimuli, and were suggested to be predominantly involved in perception of the environmental stimuli. Pattern C responses habituated least and tended to be elicited more frequently by aversive stimuli. This type of response was interpreted to reflect emotional arousal. These findings were considered to be compatible with the hypothesis that the amygdala plays an important role in converting environmental stimuli into emotions such as rage or fear.