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OBJECTIVES: Bipolar disorder (BP) is characterized by a dysfunction of mood, alternating between states of mania/hypomania and depression. Thus, the primary abnormality appears to be an inability to regulate emotion, the result of which is emotional extremes. The purpose of this paper is to review the current functional magnetic resonance imaging (fMRI) literature on adult patients with BP using emotion processing or regulation paradigms. METHODS: A search was conducted on PubMed using the keywords: bipolar disorder, fMRI, mania, bipolar depression, bipolar euthymia, emotion, and amygdala. Only those studies that were conducted in adult patients using an emotion activation task were included in the final review. RESULTS: Using tasks that assess neural functioning during emotion processing and emotion regulation, many fMRI studies have examined BP subjects during mania and euthymia. Fewer fMRI studies have been conducted during depression, and fewer still have included the same subjects in multiple mood states. Despite these limitations, these studies have demonstrated specific abnormalities in frontal-limbic regions. Using a variety of paradigms, investigators have specifically evaluated the amygdala (a structure within the limbic system known to be critical for emotion) and the prefrontal cortex (PFC) (a region known to have a regulatory function over the limbic system). CONCLUSIONS: These investigations reveal that amygdala activation varies as a function of mood state, while the PFC remains persistently hypoactivated across mood states. Emotional dysregulation and lability in mania and depression may reflect disruption of a frontal-limbic functional neuroanatomical network.
Townsend et al. (Fri,) studied this question.