Physiological Responses to Brain Stimulation During Limbic Surgery: Further Evidence of Anterior Cingulate Modulation of Autonomic Arousal

Background: In view of conflicting neuroimaging results regarding autonomic-specific activity within the anterior cingulate cortex (ACC), we investigated autonomic responses to direct brain stimulation during stereotactic limbic surgery. Methods: Skin conductance activity and accelerative heart rate responses to multi-voltage stimulation of the ACC (n = 7) and paralimbic subcaudate (n = 5) regions were recorded during bilateral anterior cingulotomy and bilateral subcaudate tractotomy (in patients that had previously received an adequate lesion in the ACC), respectively. Results: Stimulations in both groups were accompanied by increased autonomic arousal. Skin conductance activity was significantly increased during ACC stimulations compared with paralimbic targets at 2 V (2.34 ± .68 [score in microSiemens ± SE] vs. .34 ± .09, p = .013) and 3 V (3.52 ± .86 vs. 1.12 ± .37, p = .036), exhibiting a strong "voltage-response" relationship between stimulus magnitude and response amplitude (difference from 1 to 3 V = 1.15 ± .90 vs. 3.52 ± .86, p = .041). Heart rate response was less indicative of between-group differences. Conclusions: This is the first study of its kind aiming at seeking novel insights into the mechanisms responsible for central autonomic modulation. It supports a concept that interregional interactions account for the coordination of autonomic arousal.