PREFRONTAL DYSFUNCTION IN DEPRESSED-PATIENTS PERFORMING A COMPLEX PLANNING TASK - A STUDY USING POSITRON EMISSION TOMOGRAPHY

Introduction, Patients with unipolar depression show impaired performa nce on the Tower of London planning task. Positron emission tomography , which has previously identified resting state blood flow abnormaliti es in depression, was used to investigate neural activity associated w ith performance of this task in depressed patients and normal controls . Methods. Six patients with unipolar depression and six matched contr ols were scanned while performing easy and hard Tower of London proble ms in a one-touch computerized paradigm and while performing a percept uomotor control task. Results, The patients in this study showed an ex pected task-related performance deficit compared with normal subjects. In normal subjects, the task engaged a network of prefrontal cortex, anterior cingulate, posterior cortical areas and subcortical structure s including the striatum, thalamus and cerebellum. Depressed patients failed to show significant activation in the cingulate and striatum; a ctivation in the other prefrontal and posterior cortical regions was s ignificantly attenuated relative to controls. Crucially, patients also failed to show the normal augmentation of activation in the caudate n ucleus, anterior cingulate and right prefrontal cortex associated with increasing task difficulty. Conclusions, These findings provide evide nce for cingulate, prefrontal and striatal dysfunction associated with impaired task performance in depression. The present results are cons istent with a central role of cingulate dysfunction in depression as w ell as suggesting impaired frontostriatal function.