CEREBRAL PROCESSING OF NONVERBAL AFFECTIVE STIMULI: EFFECT OF A PROCESS VARIABLE ON HEMISPHERIC ASYMMETRY (EEG, CEREBRAL LATERALITY, EDA, EMOTION)

Fifty-six right handed subjects (28 males and 28 females) were recruited from undergraduate classes in the Psychology Department. Bilateral frontal lobe electroencephalographic recordings and bilateral electrodermal recordings were taken while subjects heard a series of nonverbal affective stimuli. A prior study (Meyers and Smith, in press) demonstrated that in the absence of a task these stimuli elicited bilaterally symmetrical activity as measured by overall alpha activity. The purpose of the present study was to explore the effect of manipulating a process variable on the patterns of cerebral activity. This was accomplished by the use of two different task conditions: affective and cognitive. The principal finding of the study was that the patterns of hemispheric asymmetry varied as a function of various interactions of affect, condition and gender. In all cases where hemispheric asymmetry was observed, there was greater relative left hemisphere activity than right hemisphere activity. This pattern was evident in the response of the males to the positive affect in the cognitive condition and the response of the females to the positive affect in both the affective and cognitive conditions. Males also demonstrated a small, but significant pattern of hemispheric asymmetry in response to the negative affect in the affective condition. Females demonstrated hemispheric asymmetry in response to the negative affect in the cognitive condition, whereas males did not. There was no evidence of hemispheric asymmetry in the response of males to the positive affect in the affective condition or the negative affect in the cognitive condition. In addition, the females demonstrated no hemispheric asymmetry in response to the negative affect in the affective condition.;These results indicate that future studies of cerebral laterality should employ clearly articulated and well-defined process variables in order to clarify the source of asymmetric patterns of activation.;The major electrodermal finding was that there was greater electrodermal activity on the left side during the cognitive condition and greater activity on the right side during the affective condition. The significance of this result with respect to the validity of electrodermal activity as a measure of hemispheric asymmetry remains to be elucidated.