Objective: To identify the brain regions associated with the cognitive generation of affect in hypomanic bipolar patients.
Methods: The study examined 10 hypomanic female subjects with bipolar affective disorder, and 10 age- and sex-matched comparison subjects using functional magnetic resonance imaging (fMRI) while viewing alternating blocks of captioned-pictures designed to evoke negative, positive or no affective change. The activation paradigm involved the presentation of the same visual materials over three experiments alternating (a) negative and reference, (b) positive and reference and (c) positive and negative captioned-pictures.
Results: The stimuli produced activation in both patients and comparison subjects in brain regions previously implicated in the generation and modulation of affect, in particular the prefrontal cortex. Activation in patients involved additional subcortical regions namely the caudate and thalamus.
Conclusions: This preliminary study suggests that hypomanic patients recruit additional subcortical limbic systems for emotional evaluation when advanced prefrontal cortical processing is no longer sufficient. The differential patterns of activation inform us about bipolar disorder and may have potential diagnostic and therapeutic significance.