neuroimaging studies are being conducted to learn more
about bipolar disorder Lesions in the frontal and temporal
lobes are most frequently associated with bipolar disorder.
Left-sided lesions tend to be associated with depression and
right-sided lesions with mania, though differences may be
reversed in the posterior regions of the brain (e.g., the
association of depression with right parietooccipital lesions).
No abnormalities have been found consistently via computed
tomography (CT) studies, though ventricular enlargement has
been suspected. Magnetic resonance imaging (MRI) studies
reveal an increase in white matter intensities associated with
bipolar disorder and correlated with age, though the clinical
significance is unknown. Overall, most functional imaging
studies (single-photon emission computer tomography
[SPECT] and positron emission tomography [PET]) have
noted prefrontal and anterior paralimbic hypoactivity in
bipolar depression, while preliminary studies of manic
patients have yielded inconsistent findings7
.