Hypofunction of right temporoparietal cortex during emotional arousal in depression

Context: Neuropsychological models of depression highlight temporoparietal hypofunction associated with low emotional arousal in major depressive disorder (MDD). These models were derived from indirect measures such as neuropsychological tests and electroencephalography alpha band power. Objective: To determine if high-arousing stimuli directly modulated activity in attention and arousal-related sensory brain regions in patients with MDD. Design: Between-group comparison (patients with MDD vs healthy control subjects) of neuromagnetic oscillatory activity driven by flickering emotional and neutral pictures (steady-state visual evoked fields [ssVEFs]). Setting: Center of magnetoencephalography at a public university and public ambulatory mental health service. Participants: Fifteen female low-anxious patients with MDD and 15 female controls. The groups were matched with respect to age and handedness. Intervention: Magnetoencephalographic recordings and self-report ratings. Main Outcome Measures: Modulation of current source strengths obtained by frequency domain minimum norm source localization of ssVEFs. Results: Controls and patients with MDD showed enhanced current source strengths at ssVEF frequency in occipital and parietal cortex for high-arousing emotional pictures (P<.05 for permutation statistics). While this arousal modulation in controls was pronounced in the right temporoparietal cortex, weak arousal modulation characterized that brain region in patients with MDD (F-1.28=7.2, P<.05 for interaction group by quadratic contrast). Conclusions: Although emotional pictures engaged the dorsal visual stream to a greater extent than neutral pictures in both study groups, only controls showed strong arousal modulation in the right temporoparietal cortex. Because the right temporoparietal cortex is associated with the arousal dimension of emotion, subjects with depression may have difficulties in activating arousal-related brain areas, whereas basic stimulus processing related to activation of the dorsal visual stream is intact.