Bipolar manic patients show impaired recognition and processing of negative affective stimuli as well as wide range of cognitive deficits. N400 is a negative wave elicited by contextually inappropriate word in semantic processing. We investigated the semantic processing using N400 during affective word priming paradigm in bipolar manic patients.
Eleven bipolar manic and eleven healthy subjects were participated. During affective word-word matching tasks and neutral word-word matching tasks, N400s to primed and unprimed words were recorded. Data were analyzed using repeated-measures ANOVA to assess effects of group, priming, and electrode sites separately.
Response time analysis showed a main effect of priming in neutral (p=0.001), and happy condition (p=0.001), not in sad (p=0.48) and disgusted (p=0.75). Main effect of priming was observed in controls, but not in patients to sad and disgusted. A main effect of priming was observed in neutral (F=13.0, p=0.002) not in sad, happy and disgusted condition about N400 amplitude. However, main effect of prime was observed 400 amplitude to disgusted words in controls and interaction of primed by group existed (p=0.02).Post-hoc analysis indicated that the significant difference in amplitude between control and subject was in congruent stimuli not in incongruent stimuli to neutral words. In disgusted condition, effect of prime was only observed in controls (p=0.03) not in patients (p=0.23). YMRS and SAPS subscale were correlated with N400 amplitudes at Cz electrode (p<0.05).
N400 amplitude reduction to unprimed condition of disgust might reflect affective semantic network abnormalities supporting negative bias shown in BM patients.