Prefrontal dysfunction in depressed patients performing a complex planning task: a study using positron emission tomography
R. ELLIOTT a1 , S. C. BAKER a1 , R. D. ROGERS a1 , D. A. O'LEARY a1 , E. S. PAYKEL a1 , C. D. FRITH a1 , R. J. DOLAN a1 and B. J. SAHAKIAN a1
a1 Wellcome Department of Cognitive Neurology, Institute of Neurology, MRC Cyclotron Unit, Hammersmith Hospital, University College London and Royal Free Hospital School of Medicine, London; and the Departments of Experimental Psychology and Psychiatry, University of Cambridge
Introduction. Patients with unipolar depression show impaired performance on the Tower of London planning task. Positron emission tomography, which has previously identified resting state blood flow abnormalities in depression, was used to investigate neural activity associated with performance of this task in depressed patients and normal controls.
Methods. Six patients with unipolar depression and six matched controls were scanned while performing easy and hard Tower of London problems in a one-touch computerized paradigm and while performing a perceptuomotor control task.
Results. The patients in this study showed an expected 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 structures including the striatum, thalamus and cerebellum. Depressed patients failed to show significant activation in the cingulate and striatum; activation in the other prefrontal and posterior cortical regions was significantly attenuated relative to controls. Crucially, patients also failed to show the normal augmentation of activation in the caudate nucleus, anterior cingulate and right prefrontal cortex associated with increasing task difficulty.
Conclusions. These findings provide evidence for cingulate, prefrontal and striatal dysfunction associated with impaired task performance in depression. The present results are consistent with a central role of cingulate dysfunction in depression as well as suggesting impaired frontostriatal function.
Dr R. Elliott, Wellcome Department of Cognitive Neurology, Institute of Neurology, 12 Queen Square, London WC1 3BG.