Cognitive inefficiency in depressive undergraduates: stroop processing and ERPs

Evidence from neuroimaging studies indicates that depressive symptomatology is associated with inefficient recruitment of prefrontal brain regions while performing tasks that tax executive function. In the current study, we investigated the time-course and ERP signature of inefficient executive functioning using a verbal Stroop color-naming task. Twenty (20) undergraduates with moderate to severe BDI-II depression scores and 20 low-scoring controls completed the task. Performance measures did not differ between the two groups. Overt reaction and P300 latencies indicated that all participants showed prominent Stroop effects, such that incongruent responses were delayed compared to congruent. Effects of task condition on the frontal N450 indicated that depressive participants differentiated congruent and incongruent trials earlier than did controls, and that the size of the congruency effect on the N450 was related to self-reported trait rumination among depressive participants. Following this effect, depressive participants showed larger P300s, suggesting an over-commitment of cognitive control resources in the depressive participants. These data lend further evidence to the cortical inefficiency hypothesis and extend the literature by indicating possible improper timing of neural activations during an executive task in depressive undergraduates.