Intracerebral source localization of mental process-related potentials elicited prior to mental sweating response in humans.

We measured the mental sweating response (MSR) and the skin sympathetic nerve activity (SSNA). Mental arithmetic or recall questions first elicited SSNA and then elicited MSR. MSR was used as the trigger point of time 0 ms to average EEGs. The averaged EEGs contained slow wave fluctuations, which occurred 5 s prior to the MSR onset. The current source locations of the MSR-related potentials were estimated by EEG dipole tracing method in two subjects. Mental stress activated the inferior frontal gyrus 5.5 s prior to the MSR and then 0.5 s later, the lateral part of the hippocampus in a subject, and they activated the medial part of the amygdala 5 s prior to the MSR in another subject. Indirect contact of the brain with the mind associated with mental questions was discussed.