Limbic hyperreactivity in bipolar II disorder.

Abstract

The authors' goal was to determine whether patients with bipolar II disorder had altered regional brain responses to novel motor sequences. Regional cerebral blood flow was measured with positron emission tomography in 13 patients with bipolar II disorder and 14 healthy comparison subjects. Participants performed a serial reaction time task in which they were visually cued to press one of four buttons at a time. The order of button presses was determined by a complex sequence that was changed in the latter half of the study. In the comparison subjects a spatial attention circuit in the superior parietal lobe and supplementary motor area was activated in response to the introduction of the new sequence. Patients did not display this activation pattern; instead, a widespread limbic network was activated in response to the new sequence. The attentional resources of patients with bipolar II disorder are not reallocated when they are confronted with a nonemotional motor task; rather, their performance is altered through activation of limbic circuitry.