Latency of alpha blocking as a function of photic stimulation during the cardiac cycle

Cortical initiation of phasic electrodermal activity

In order to investigate the role of the cerebral cortex in elicitation of spontaneous electrodermal responses (EDRs), electrocortical activity (EEG) preceding peripheral fluctuations was investigated. During one 30-min session, subjects imagined arousing situations. EEG and EDR average waveforms were computed with respect to the EDR maxima. In Grand Average EEG waveforms, transient activity preceding EDR onset at about 2.3 seconds, lasting for about 1 s, was observed. The main power of this phasic event was in the alpha frequency band. Digital filtering of EEG waveforms supported the assumption of a visceral control process at cortical level, responsible for triggering peripheral EDRs. Whereas the phenomenon occurred slightly earlier frontally than centrally, it was strongest at the vertex. The possible interpretation of this electrocortical phenomenon, related to the evocation of electrodermal responses, as a final common pathway of different EDR generating systems is discussed.