Background: Patients with mania show a behavioral bias toward positive information in an emotional go/no go task. This is the converse of the bias toward negative information seen in unipolar depression that we have recently related to the abnormal function of ventral and medial prefrontal cortices (PFCs). The aim of this study was to investigate the neuronal basis of the bias toward positive information in manic patients.

Methods: During performance of an emotional go/no go task using functional magnetic resonance imaging, 8 manic patients and 11 healthy controls were scanned. The task allowed comparison between neural response to happy, sad, and neutral words in the context of these words being either targets or distracters.

Results: Manic patients showed attenuated orbitofrontal response when all the semantic conditions were compared with a control condition; however, they showed an enhanced response of the left ventrolateral PFC to emotional relative to neutral targets, as well as enhanced ventral and medial prefrontal response to emotional, particularly happy, distracters.

Conclusions: These results suggest a critical role for ventral and medial dysfunction in the pathology of mania, which might underpin aspects of cognitive and clinical symptomatology.