Original article
Abnormal pattern of cerebral activity during a spatial imagery task in unipolar depressed patients: ^99mHMPAO SPECT study

The effect of performance on simple spatial imagery task on regional cerebral blood flow was measured in patients with major depressive disorder and in a control group by means of HMPAO-SPECT. Ten untreated patients who met DSM-IV criteria for major depressive episode, recurrent, and ten healthy subjects, age and sex matched, participated in the study. During each session, subjects were scanned twice: under basal condition after injection of 10 mCi of ^99mHMPAO while repeating words and again during spatial imagery of geometrical figures after injection of 30 mCi of ^99mHMPAO. In the patient group the same procedure was performed in an acute depressive episode and during remission of depressive symptoms. During the depressive episode, there was no significant activation of frontal and parieto-occipital areas of the right hemisphere, the regions that were activated in healthy control subjects. Instead, during depression activation was observed in the left hemisphere. In remission, the regions of the right hemisphere were activated in depressive patients but the pattern of activation was different in comparison to control subjects. The results may support the hypothesis of abnormal function of the right hemisphere in depressed patients.