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“A context-dependent switch from sensing to feeling in the primate amygdala”

Katalin M. Gothard, M.D., Ph.D.

Professor of Physiology, Neurology, and Neuroscience The University of Arizona College of Medicine Department of Physiology

Abstract:

Tactile signals elicited in the periphery by social and affective touch acquire emotional significance in the brain. As the amygdala processes the valence of all sensory stimuli, we predicted that the positive valence of grooming would strongly activate the monkey amygdala. To test this hypothesis, we compared neural activity in the amygdala and the primary somatosensory cortex in response to social grooming and gentle airflow delivered to the same areas of the skin. Neurons in the somatosensory cortex responded to both types of tactile stimuli. In the amygdala, however, neurons did not respond to individual grooming sweeps even though grooming elicited autonomic states indicative of positive affect. Instead of responses to individual touch stimuli, a large proportion of neurons showed enhanced or suppressed baseline firing rates that persisted throughout a grooming bout. These changes were attributed to social context because the presence of the groomer alone could account for increases or decreases in baseline firing rates. It appears, therefore, that during grooming, the amygdala stops responding to external inputs on a short time scale but remains responsive to social context, and the associated affective states, on longer time scales.