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

Abstract

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. 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. 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. 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.