Journal of the International Neuropsychological Society



Is there disproportionate impairment in semantic or phonemic fluency in schizophrenia?


WILLIAM S.  KREMEN  a1 c1, LARRY J.  SEIDMAN  a2, STEPHEN V.  FARAONE  a2 and MING T.  TSUANG  a2
a1 Department of Psychiatry, University of California, Davis School of Medicine, 2230 Stockton Blvd., Sacramento, CA, and UC Davis–Napa Psychiatric Research Center, Napa State Hospital, Napa, CA
a2 Harvard Medical School Department of Psychiatry at Massachusetts Mental Health Center, Brockton-West Roxbury VA Medical Center and Massachusetts General Hospital, and Harvard Institute of Psychiatric Epidemiology and Genetics, 74 Fenwood Road, Boston, MA

Abstract

Phonemic and semantic fluency involve the capacity to generate words beginning with particular letters or belonging to particular categories, respectively. The former has been associated with frontal lobe function and the latter with temporoparietal function, but neuroimaging studies indicate overlap of underlying neural networks. Schizophrenia patients may experience disproportionate semantic fluency impairment owing to abnormal semantic organization; however, executive dysfunction in schizophrenia suggests possible disproportionate phonemic fluency impairment. Moreover, little is known about the diagnostic specificity of either verbal fluency deficit to schizophrenia or their stability over time. We examined 83 schizophrenia patients, 15 bipolar disorder patients, and 83 normal controls. Both fluency types were impaired in schizophrenia patients. Schizophrenia patients as a whole manifested disproportionate semantic fluency impairment relative to bipolar disorder patients, but only a subset of schizophrenia patients manifested disproportionate semantic fluency impairment relative to controls. Few characteristics, except to some extent paranoid-nonparanoid subtype, meaningfully differentiated schizophrenia patients with and without this disproportionate impairment. Verbal fluency measures were moderately stable over a 4-year period in schizophrenia patients and controls (.48 < rs < .79). These results mirror a literature that overall suggests a small degree of disproportionate semantic fluency impairment in schizophrenia, but also some heterogeneity in fluency deficits. (JINS, 2003, 9, 79–88.)

(Received September 19 2001)
(Revised February 4 2002)
(Accepted March 2 2002)


Key Words: Verbal fluency; Semantic memory; Frontal cortex; Temporoparietal cortex; Schizophrenia.

Correspondence:
c1 Reprint requests to: William S. Kremen, Ph.D., Department of Psychiatry, University of California, Davis School of Medicine, 2230 Stockton Boulevard, Sacramento, CA 95817. E-mail: wskremen@ucdavis.edu


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