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.

From the heart to the brain: a study of heartbeat contingent scalp potentials.

Heartbeat perception has become the most widely studied example of visceral perception. In the present study scalp potentials contingent to the visceral event "heartbeat" were investigated. Scalp potentials, averaged time-locked to the EKG-R-wave, were studied at Fz, Cz, and Pz under four conditions: resting (baseline), heartbeat discrimination task, signal detection task, and heartbeat discrimination task after physical exercise. 22 subjects were assigned to the two groups "good" and "poor" perceivers, according to their performance in an initial heartbeat perception test. Event related potentials (ERPs) of "good" perceivers were more stable across conditions than those of "poor" perceivers. Peak latency within the range of 200 to 300 ms differed significantly between conditions. A principal component analysis performed on the ERP averages extracted five components. Subsequent ANOVAs across factor scores yielded significant main effects for the "groups" factor, experimental conditions and electrode sites. The strongest effects occurred over the frontal region in the latency range of 250-400 ms (following the EKG-R-wave). These were found to be not due to artifactual EKG influences.

A comparative investigation of ERP components and the SCR in a habituation and dishabituation paradigm.

The present experiment investigated the trial-by-trial habituation in the event-related potential (ERP) and the skin conductance response (SCR) to repeated stimuli and dishabituation to rare stimuli. In a balanced design, two groups of subjects passively observed either large black discs as repeated stimuli and small as rare, or vice versa. No consistent effects of stimulus size were obtained between the groups. Late positivity was composed of a double peak at Cz, containing contributions from P3a and P300; the latter only was observed at Pz. The SCR and P3a and P300 at Cz demonstrated habituation, but not the N100 or P200, nor the P300 at Pz. Rare stimuli elicited an enhancement, albeit nonsignificant, in SCR amplitude only. No dishabituation of any of the responses by these stimuli was observed. The SCR correlated significantly with late positivity at Cz and Pz. Discussion focuses on SCR and late positivity as OR components.