Brain imaging in the search for biological markers in affective disorder.

Positron emission tomography with 18fluorodeoxyglucose provides the possibility of obtaining detailed noninvasive images of the brain's metabolic rate in patients with affective disorder. The close correspondence between brain work and metabolic rate allows the researcher to assess brain functional activity and its changes with drug treatment or even sleep. Initial studies have revealed that the metabolic rate in frontal cortex relative to parietal and occipital cortex is lower in patients with bipolar affective disorder than in normal controls. A small sample of unipolar patients showed a relatively higher frontal cortex metabolic rate than normal controls. Bipolar patients also showed metabolic rates in the basal ganglia relative to whole slice metabolism to be low in comparison to normal controls. Antidepressant drugs appeared to have their greatest effects in the frontal lobes.