Changes in autonomic responsiveness following bilateral amygdalotomyin humans

Although reports of human amygdalotomy for intractable behavioral disturbances generally indicate positive outcomes regarding diminished episodes of rage, the mechanisms by which these changes occur are not well understood. The amygdala has been described as a sensory modulator of emotional responses, and its importance in mediating certain autonomic nervous system functions may account, in part, for this functional description. In order to examine the amygdala's role in autonomic activity, we measured autonomic responsiveness and habituation in a patient who underwent bilateral amygdalotomy for intractable aggression. Preoperatively, there was no evidence of electrodermal response habituation, whereas postoperatively, habituation occurred normally. Electrodermal response, frontal electromyography, and hand temperature showed a consistent change, indicating diminished autonomic levels following surgery. These findings suggest that the beneficial results reported for bilateral amygdalotomy in reducing episodes of aggression may be associated with diminished autonomic responsiveness.