THE INTERACTION BETWEEN MOOD AND COGNITIVE FUNCTION STUDIED WITH PET

Background. Experimentally induced depressed mood is a suggested model for retarded depression. We describe the neural response associated w ith induced mood and the locus of the interaction between systems medi ating mood and cognitive function. Methods. Normal subjects performed a verbal fluency task during induced elated and depressed mood states. Regional cerebral blood flow (rCBF) was measured as an index of neura l activity using Positron Emission Tomography (PET). Results. In both elated and depressed mood state rCBF was increased in lateral orbitofr ontal cortex, rCBF was also increased in the midbrain in elated mood. In the depressed condition rCBF was decreased in rostral medial prefro ntal cortex. Verbal fluency produced an expected increase of rCBF in l eft dorsolateral prefrontal, inferior frontal and premotor cortex, ant erior cingulate and insula cortex bilaterally, the left supramarginal gyrus posteriorly and the thalamus. Activation in the verbal fluency t ask was attenuated throughout the left prefrontal, premotor and cingul ate cortex and thalamus in both elated and depressed mood conditions. An attenuation of anterior cingulate activation was specific to depres sed mood. Conclusions. Alteration of mood is associated with activatio n of orbitofrontal cortex which may be critical to the experience of e motion. The mood induced modulation of verbal fluency induced activati ons is consistent with resting state findings of decreased function in these regions in depressed patients. The present data suggest that re sting slate rCBF profile may represent the modulation of spontaneous a ctivity in this network by a core system that is dysfunctional in depr ession.