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151. The Impact of Acute Stress on Neurophysiological and Behavioral Indices of Motivation in Individuals with Depression
The current study examined the relation of stress exposure and a heightened stress response to approach and avoidance motivation in depression. Motivation was defined neurophysiologically as greater relative left frontal EEG alpha asymmetry recorded pre- and post-stressor and behaviorally as willingness to expend effort for reward or to prevent loss on a modified version of the Effort Expenditure for Rewards Task (EEfRT). Stress exposure was operationalized as random assignment to a social exclusion condition versus an inclusion condition in the Cyberball task. Stress response was operationalized as participants’ scores on the Need Threat Scale post-Cyberball. Depressed participants (n= 57) showed lower relative left baseline frontal EEG asymmetry than non-depressed participants (n= 44), F(1, 96)=6.16, p=.015, and showed lower approach, b= -0.36, p<.001, and avoidance motivation, b= -0.39, p<.001, on the EEfRT compared to non-depressed participants. Stress exposure and a higher stress response related to increased relative left frontal EEG asymmetry following the stress task, F(1, 96)=4.50, p=.048; B= -0.23, t(95)= -2.25, p=.027. Further, stress exposure related to increased avoidance motivation on the EEfRT in the full sample, b=0.23, p=.045. A heightened stress response was related to increased avoidance, b= -0.16, p=.012, but decrease approach motivation, b=0.12, p=.001, in depressed participants.