Early ERP modulation during mood adjectives processing in patients with affective disorders.

Attentional bias is considered a key feature in mood disorders, and yet little is known of its neural correlates within the early stream of information processing in manic and depressed patients. The study aimed to capture and detail attentional bias during emotional word processing in patients within the first 500ms of stimulus exposition. 28 mood adjectives (14 positive and 14 negative) were used as stimuli. We expected differences in adjective encoding between groups during lexico-semantic analysis based on varying attentional resource allocation. Differences were evidenced within the first 100ms after stimulus onset with higher amplitudes for both patient groups than controls, possibly indicating more automatic attention allocation to stimuli during sensory analysis stages. Between 200-290ms after the words' onset, a specific valence mood-word mismatch was registered which approached significance, with higher responses evoked to negative than positive words in manic patients, and the opposite pattern of activity observed in depressed patients, suggesting cognitive bias based on mood incongruence during the lexico-semantic analysis stage. There was also a lateralized pattern of activity, with higher amplitudes over the right hemisphere posteriorly, and higher over the left frontally in the patient groups, especially in the manic individuals. The study points to attentional bias based on mood incongruence processing during crucial stages of meaning encoding within the early stream of information processing.