Semantic memory impairment in schizophrenia — Deficit in storage or access of knowledge? O.J. Doughty a , D.J. Done a, ⁎ , V.A. Lawrence a , A. Al-Mousawi b , K. Ashaye c a University of Hertfordshire, Hatfield, UK b Northwick Park Hospital, Harrow, UK c Mental Health Unit, Lister Hospital, Stevenage, UK Received 16 October 2007; received in revised form 18 April 2008; accepted 28 April 2008 Available online 26 July 2008 Abstract This study evaluates whether patients with schizophrenia have a degraded memory store for semantic knowledge. 20 patients with a chronic history of schizophrenia and evidence of cognitive impairment were selected, since the literature indicates that this subgroup is most likely to manifest a degraded semantic knowledge store. Their profile of semantic memory impairments was compared to that of a group of Alzheimer's Dementia (AD) patients (n = 22), who met neuropsychological criteria for degraded semantic store. Both groups were matched for Performance IQ. 15 elderly healthy controls were also included in the study. The AD and schizophrenia groups produced substantially different profiles of semantic memory impairment. This is interpreted as indicating that the semantic impairments in this subgroup of patients with schizophrenia do not result from a degraded store. This is corroborated by an analysis of the data using other neuropsychological criteria for determining degraded store. We conclude that there is little evidence for a classic degradation of semantic knowledge in schizophrenia, and it appears that impairments result from an inability to use semantic knowledge appropriately, particularly when selection of salient semantic relations is required. © 2008 Elsevier B.V. All rights reserved. Keywords: Schizophrenia; Semantic memory; Alzheimer's Dementia; Executive function; IQ 1. Introduction Semantic memory refers to the memory store that holds general, rather than autobiographical knowledge, most no- tably word meanings and object concepts. Impaired seman- tic memory has been frequently reported in schizophrenia across a range of different tests (McKay et al., 1996; Chen et al., 1994; Al-Uzri et al., 2004; Bokat and Goldberg, 2003; Spitzer et al., 1993) and is thought to provide a plausible cognitive model for delusions and formal thought disorder (Goldberg et al., 1998; Rossell et al., 1999). On the one hand, evidence points to degraded representations in the semantic memory store of patients with schizophrenia (Laws et al., 1998; Rossell and David, 2006). However other studies suggest impaired access from an otherwise intact, and well organized, semantic store (Allen et al., 1993; Joyce et al., 1996). This inconsistency probably reflects the heterogeneity of schizophrenia and concomitant neurocognitive dysfunction (e.g. Bilder et al., 2000). The majority of studies reporting a degraded storage disorder in schizophrenia have recruited patients with both a chronic history and accompanying cognitive impairments (e.g. Chen et al., 2000; Laws et al., 1998; Rossell and David, Available online at www.sciencedirect.com Schizophrenia Research 105 (2008) 40 – 48 www.elsevier.com/locate/schres ⁎ Corresponding author. Tel.: +44 1707 284638. E-mail address: d.j.done@herts.ac.uk (D.J. Done). 0920-9964/$ - see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.schres.2008.04.039