Magnetic resonance imaging brain activation in first-episode bipolar mania during a response inhibition task

Abstract

Aims: Impulsivity is common in bipolar disorder, especially during mania. Understanding the functional neuroanatomy of response inhibition, one component of impulsivity, might clarify the neural substrate of bipolar disorder.

Methods: Sixteen DSM-IV first-episode, manic bipolar patients and 16 matched healthy subjects were examined during a first manic episode using functional magnetic resonance imaging while performing a response inhibition task. All subjects were studied using a 4.0 Tesla Varian Unity INOVA Whole Body MRI/MRS system. The response inhibition task was presented using non-ferromagnetic goggles, and task performance was recorded during scan acquisition. Imaging data were analysed using analysis of functional neuroimages. Group contrasts were made for the specific response inhibition measure.

Results: The groups performed the task similarly, although both demonstrated relatively poor rates of target response, but high rates of successful 'stops'. Despite similar behavioural results, the groups showed significantly different patterns of functional magnetic resonance imaging brain activation. Specifically, during response inhibition, the healthy subjects exhibited significantly greater activation in anterior and posterior cingulate, medial dorsal thalamus, middle temporal gyrus, and precuneus. The bipolar patients exhibited prefrontal activation (BA 10) that was not observed in healthy subjects.

Conclusions: Bipolar and healthy subjects exhibit different patterns of brain activation to response inhibition; these differences may reflect different functional neuroanatomic approaches to response inhibition between the two groups.

Keywords: anterior cingulate; bipolar disorder; fMRI; first-episode mania; response inhibition; stop-signal.

Figure 1

Activation during response inhibition in 16 healthy subjects. Orange tones indicate regions of increased activation, blue tones are areas of decreased activation.

Figure 2

Activation during response inhibition in 16 bipolar manic subjects. Orange tones indicate regions of increased activation, blue tones are areas of decreased activation.

Figure 3

Difference in fMRI activation in 16 first-episode bipolar manic patients and 16 matched healthy subjects. Orange tones indicate regions with increased activation in the healthy subjects.

Figure 4

Differences in fMRI activation in 8 patients off medication versus 8 patients on medications during response inhibition. Blue indicates regions of greater activation in unmedicated patients, red indicates regions of greater activation in medicated patients.