Bilateral electrodermal activity: relationships to state and trait characteristics of hemisphere asymmetry.

ABSTRACT

Influences of trait and state characteristics of individual brain lateralization on bilateral electrodermal activity (EDA) were examined. EDA was observed in two different recording conditions (1) non-specific skin conductance responses (ns.SCRs) were obtained during a stimulus-free recording period of 5 min; and (2) stimulus evoked skin conductance responses (SCRs) were elicited by 80 dichotically presented pairs of pure tones which--at the same time--constituted the items of a test to estimate subject's lateral ear dominance. In addition to ear dominance, degree of right-handedness and hemispheric preference, i.e. preferred direction of conjugate lateral eye movements (CLEMs) were assessed as trait-like characteristics of individual laterality. With respect to asymmetry of ns.SCRs, no effects of the laterality variables were observed. Analysis of SCRs, however, resulted in significant interactions of ear dominance and hemispheric preference with degree of right-handedness indicating higher SCR amplitudes on the hand contralateral to the preferred hemisphere in strong dextrals. Weak right-handers showed a different pattern of bilateral asymmetries, partly in the opposite direction. Additionally, phasic effects of cortical asymmetry on SCRs seem to be modified by trait characteristics of individual laterality. Results underline the importance of precisely controlling degree of handedness in studies of bilateral electrodermal activity. Furthermore, the observed effects support the assumption of cortical influences on EDA, but argue against the existence of a single cortical mechanism modulating asymmetries in the electrodermal system.