RESPONSES OF SINGLE NEURONS IN AMYGDALA TO INTEROCEPTIVE AND EXTEROCEPTIVE STIMULI IN CONSCIOUS CATS

The amygdala is critical for behavioral arousal and must therefore int egrate a wide variety of inputs. We examined sensory inputs and the de gree of convergence to single neurons in the amygdala in conscious fre ely moving cats. A presser stimulus elicited responses, predominantly inhibitory, in one-half of the amygdalar neurons tested. Most neurons in the central and basal nuclei responded to carotid chemoreceptor act ivation typically with an excitation. Almost one-half of all amygdalar neurons tested, particularly in the central nucleus, received orthodr omic input from the locus ceruleus, the substantia nigra, and/or the c ontralateral central nucleus of the amygdala. Exteroceptive sensory st imulation with optic, acoustic, tactile, and olfactory stimuli elicite d responses in 33, 55, 39, and 59% of amygdalar neurons, respectively. Two-thirds of the neurons tested with more than one external stimulus modality responded in the same manner to the various stimuli (usually excitation), demonstrating a convergence of exteroceptive stimuli on single amygdalar neurons, particularly in the basal nucleus. Spontaneo us and induced behavioral arousal elicited responses in 92 and 86% of neurons, respectively. Most neurons responded to multimodal exterocept ive stimuli and behavioral arousal in the same manner. We suggest that amygdalar inputs are highly varied and, in many cases, relatively non specific and that the amygdala integrates a large number of external a nd internal sensory modalities to regulate autonomic and behavioral re sponsiveness to various stimuli.