lunted Activation in Orbitofrontal Cortex uring Mania: A Functional Magnetic Resonance maging Study

ackground: Patients with bipolar disorder have been reported to have abnormal cortical function during mania. In this study, we ought to investigate neural activity in the frontal lobe during mania, using functional magnetic resonance imaging (fMRI). pecifically, we sought to evaluate activation in the lateral orbitofrontal cortex, a brain region that is normally activated during ctivities that require response inhibition. ethods: Eleven manic subjects and 13 control subjects underwent fMRI while performing the Go-NoGo task, a neuropsychological aradigm known to activate the orbitofrontal cortex in normal subjects. Patterns of whole-brain activation during fMRI scanning were etermined with statistical parametric mapping. Contrasts were made for each subject for the NoGo minus Go conditions. Contrasts ere used in a second-level analysis with subject as a random factor. esults: Functional MRI data revealed robust activation of the right orbitofrontal cortex (Brodmann’s area [BA] 47) in control subjects ut not in manic subjects. Random-effects analyses demonstrated significantly less magnitude in signal intensity in the right lateral rbitofrontal cortex (BA 47), right hippocampus, and left cingulate (BA 24) in manic compared with control subjects. onclusions: Mania is associated with a significant attenuation of task-related activation of right lateral orbitofrontal function. This ack of activation of a brain region that is usually involved in suppression of responses might account for some of the disinhibition seen n mania. In addition, hippocampal and cingulate activation seem to be decreased. The relationship between this reduced function nd the symptoms of mania remain to be further explored.