Impaired filtering of irrelevant information in dysphoria: an ERP study

Behavioural findings have led to proposals that difficulties in attention and concentration in depression may have their roots in fundamental inhibitory impairments for irrelevant information. These impairments may be associated with reduced capacity to actively maintain relevant information to facilitate goal-directed behaviour. In light of mixed data from behavioural studies, the current study using direct neural measurement, examines whether dysphoric individuals show poor filtering of irrelevant information and reduced working memory (WM) capacity for relevant information. Consistent with previous research, a sustained event-related potential (ERP) asymmetry, termed contra-lateral delay activity (CDA), was observed to be sensitive to WM capacity and the efficient filtering of irrelevant information from visual WM. We found a strong positive correlation between the efficiency of filtering irrelevant items and visual WM capacity. Specifically, dysphoric participants were poor at filtering irrelevant information, and showed reduced WM capacity relative to high capacity non-dysphoric participants. Results support the hypothesis that impaired inhibition is a central feature of dysphoria and are discussed within the framework of cognitive and neurophysiological models of depression.