Elucidating semantic disorganisation from a word comprehension task: Do patients with schizophrenia and bipolar disorder show differential processing of nouns, verbs and adjectives? Susan L. Rossell a,b,c, ⁎ , Rachel A. Batty c a Macquarie Centre for Cognitive Science (MACCS), Macquarie University, Sydney, NSW 2109, Australia b Section of Cognitive Neuropsychiatry, Psychological Medicine, Institute of Psychiatry, De Crespigny Park, London, UK c Cognitive Neuropsychiatry Laboratory, Alfred Psychiatry Research Centre, School of Psychology, Psychiatry and Psychological Medicine, Monash University, 1st Floor, Old Baker Building, The Alfred Hospital, Commercial Road, Melbourne, VIC 3004, Australia Received 16 August 2006; received in revised form 2 April 2008; accepted 8 April 2008 Available online 20 May 2008 Abstract Memory deficits have been reported in schizophrenia and bipolar disorder. However, the precise impact of semantic memory deficits on word comprehension, particularly across grammatical categories, has not been adequately investigated in these disorders. Furthermore, previous studies examining semantic memory have predominantly been designed so that most healthy controls perform at ceiling, questioning the validity of observed differences between patient and control groups. A new word definition task examined word comprehension across grammatical categories, i.e. nouns, verbs and adjectives, and was designed to overcome the ceiling effect. It was administered to 32 schizophrenia patients, 28 bipolar disorder patients and 32 matched healthy controls. Schizophrenia patients had a global impairment on the task but bipolar patients were only impaired on a recognition memory component. Word comprehension, however, across grammatical categories was comparable across groups. © 2008 Elsevier B.V. All rights reserved. Keywords: Schizophrenia; Bipolar disorder; Word comprehension; Semantic disorganisation 1. Introduction Semantic memory refers to an individual's stored knowledge. It is impersonal and includes knowledge of words and their meanings, knowledge of objects and their interrelationships, and general knowledge about the world. Abnormalities in semantic memory are commonly proposed to be central to cognitive abnorm- alities in schizophrenia, with deficits being reported on a wide variety of tasks, for example, categorisation (Rossell and David, 2006), fluency (Rossell et al., 1999) and priming (Rossell et al., 2000). Semantic deficits are, consequently, predicted to underlie disturbances in thought and language in schizophrenia, which might not only explain the deficits observed in other cognitive domains (i.e. reasoning), but also provide a cognitive explanation for common symptoms in schizophrenia, for example, delusions, thought disorder and alogia. While memory deficits in bipolar disorder are also reported, the impact of semantic memory deficits in bipolar has not Available online at www.sciencedirect.com Schizophrenia Research 102 (2008) 63 – 68 www.elsevier.com/locate/schres ⁎ Corresponding author. Cognitive Neuropsychiatry Laboratory, Alfred Psychiatry Research Centre, School of Psychology, Psychiatry and Psychological Medicine, Monash University, 1st Floor, Old Baker Building, The Alfred Hospital, Commercial Road, Melbourne, VIC 3004, Australia. Tel.: +61 3 9076 8650; fax: +61 3 9207 1545. E-mail address: srossell@srossell.com (S.L. Rossell). 0920-9964/$ - see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.schres.2008.04.008