Individual differences in electrodermal and electroencephalographic asymmetries.

In a continuing investigation of the relationship between differential hemispheric activation and electrodermal asymmetry, comparisons were made between the electroencephalographic asymmetries and electrodermal asymmetries exhibited by subjects carrying out particular tasks. Bilateral skin conductance responses and 28 channels of EEG data allowing the production of topographical maps were collected from 8 female and 8 male right-handed subjects during the performance of two tasks, one verbal and one visuospatial. The tasks were selected with the aim of differentially activating the hemispheres to investigate whether parallel changes in the direction of electroencephalographic and electrodermal asymmetries would occur. EEG asymmetries were compared in female and male subjects. Previous research has indicated that males tend to show stronger EEG asymmetry than females, and that this is emphasised in verbal tasks. This was confirmed by the present study. Comparison with electrodermal activity revealed a weak relationship between the two measures, with some parallels between task-related variations in the beta 2 waveband and skin conductance responses. No parallels between alpha activity or skin conductance level were demonstrated. If the subjects are regrouped according to degree of electrodermal asymmetries, then some closer parallels with electroencephalographic asymmetries are revealed with more marked electrodermal asymmetry paralleling more marked electroencephalographic asymmetry. Variations in electrodermal asymmetry appear to be related to greater activity on the hand contralateral to the hemisphere showing smaller amplitude EEG activity, generally in the beta waveband. In discussing cortical control of electrodermal activity, these findings are discussed in terms of both the contralateral excitatory and the contralateral inhibitory models.