This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (3) Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Covington, M. A. Articles by Brown, J. Search for Related Content PubMed PubMed Citation Articles by Covington, M. A. Articles by Brown, J. Social Bookmarking                         What's this?

Does ketamine mimic aspects of schizophrenic speech?

CASPR, Artificial Intelligence Center, University of Georgia, Athens, Georgia, USA, mc{at}uga.edu

Wim J. Riedel

GlaxoSmithKline Research & Development Ltd., Addenbrooke's Hospital, Cambridge, UK

Cati Brown

CASPR, Artificial Intelligence Center, University of Georgia, Athens, Georgia, USA

Congzhou He

CASPR, Artificial Intelligence Center, University of Georgia, Athens, Georgia, USA

Eric Morris

CASPR, Artificial Intelligence Center, University of Georgia, Athens, Georgia, USA

Sara Weinstein

Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada

James SempLe

GlaxoSmithKline Research & Development Ltd., Addenbrooke's Hospital, Cambridge, UK

John Brown

GlaxoSmithKline Research & Development Ltd., Addenbrooke's Hospital, Cambridge, UK

Speech disturbances are well-known symptoms contributing to the diagnosis of schizophrenia. Subanesthetic doses of the N-methyl-D-aspartate (NMDA) antagonist ketamine have been reported to produce positive and negative symptoms and cognitive impairments consistent with those seen in schizophrenia. Insofar as this is true, it constitutes evidence that the NMDA system is involved in schizophrenia. It is therefore of interest to know whether ketamine produces speech disturbances like those of schizophrenia.

Quantitative computer-aided analysis of apparently normal speech can detect clinically relevant changes and differences that are not noticeable to the human observer.

Accordingly, in this study, speech samples were analysed for repetitiousness, idea density, and verb density using software developed by the authors. The samples came from two experiments, a within-subjects study of healthy volunteers given intravenous ketamine versus placebo, and a between-groups study of patients diagnosed with schizophrenia and comparable healthy controls.

Our primary hypothesis was that in both schizophrenia and ketamine, repetitiousness wouLd increase, since perserverative speech is a well-known symptom of schizophrenia. Our secondary hypotheses were that in both schizophrenia and ketamine, idea density and verb density would decrease as indicators of cognitive impairment.

The primary hypothesis was confirmed in the schizophrenia experiment (between groups) and the ketamine experiment (within subjects).

The secondary hypotheses were disconfirmed except that in the ketamine experiment, verb density was significantly lowered. Reduced use of verbs apparently reflects a cognitive impairment of a different type than repetitiousness, and further investigation is needed to determine whether this impairment occurs in psychosis.

Key Words: ketamine • schizophrenia • N-methyl-D-aspartate (NMDA) • speech • Language • verbal behavior • perseveration • verbs • idea density

Journal of Psychopharmacology, Vol. 21, No. 3, 338-346 (2007)
DOI: 10.1177/0269881107077729


CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				M. Covington, W. Riedel, C. Brown, C. He, E. Morris, S. Weinstein, J. Semple, and J. Brown Ketamine and schizophrenic speech: more difference than originally reported J Psychopharmacol, January 1, 2009; 23(1): 111 - 112. [PDF]

				C. BROWN, T. SNODGRASS, S. J. KEMPER, R. HERMAN, and M. A. COVINGTON Automatic measurement of propositional idea density from part-of-speech tagging Behav Res Methods, May 1, 2008; 40(2): 540 - 545. [Abstract] [PDF]