Psychological Medicine

  • Psychological Medicine / Volume 39 / Issue 11 / November 2009, pp 1799-1808
  • Copyright © Cambridge University Press 2009. The online version of this article is published within an Open Access environment subject to the conditions of the Creative Commons Attribution-NonCommercial-ShareAlike licence <http://creativecommons.org/licenses/by-nc-sa/2.5/>. The written permission of Cambridge University Press must be obtained for commercial re-use.
  • DOI: http://dx.doi.org/10.1017/S0033291709005935 (About DOI), Published online: 07 May 2009
  • OPEN ACCESS

Original Articles

Dissociation of long-term verbal memory and fronto-executive impairment in first-episode psychosis

V. C. Leesona1a2 c1, T. W. Robbinsa3, C. Franklina2, M. Harrisona2, I. Harrisona2, M. A. Rona1, T. R. E. Barnesa2 and E. M. Joycea1

a1 Institute of Neurology, University College London, UK

a2 Imperial College Faculty of Medicine, London, UK

a3 Department of Experimental Psychology, University of Cambridge, UK

Abstract

Background Verbal memory is frequently and severely affected in schizophrenia and has been implicated as a mediator of poor clinical outcome. Whereas encoding deficits are well demonstrated, it is unclear whether retention is impaired. This distinction is important because accelerated forgetting implies impaired consolidation attributable to medial temporal lobe (MTL) dysfunction whereas impaired encoding and retrieval implicates involvement of prefrontal cortex.

Method We assessed a group of healthy volunteers (n=97) and pre-morbid IQ- and sex-matched first-episode psychosis patients (n=97), the majority of whom developed schizophrenia. We compared performance of verbal learning and recall with measures of visuospatial working memory, planning and attentional set-shifting, and also current IQ.

Results All measures of performance, including verbal memory retention, a memory savings score that accounted for learning impairments, were significantly impaired in the schizophrenia group. The difference between groups for delayed recall remained even after the influence of learning and recall was accounted for. Factor analyses showed that, in patients, all variables except verbal memory retention loaded on a single factor, whereas in controls verbal memory and fronto-executive measures were separable.

Conclusions The results suggest that IQ, executive function and verbal learning deficits in schizophrenia may reflect a common abnormality of information processing in prefrontal cortex rather than specific impairments in different cognitive domains. Verbal memory retention impairments, however, may have a different aetiology.

(Received November 07 2008)

(Revised March 03 2009)

(Accepted March 18 2009)

(Online publication May 07 2009)

Correspondence

c1 Address for correspondence: Dr V. C. Leeson, UCL Institute of Neurology, Room 807 Queen Square House, 22 Queen Square, London WC1N 3BG, UK. (Email: v.leeson@ion.ucl.ac.uk)

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