Component analysis of verbal fluency in patients with schizophrenia

Objective: Clustering and switching components of phonemic fluency performa nce were compared in patients with schizophrenia and healthy normal control s. Background: These components were selected to provide evidence for a spe cific anatomic locus for the breakdown of language processes or for a multi ple-disease model of schizophrenia. Method: As part of a larger battery of neuropsychological tests, phonemic fluency tests were administered on an in dividual basis. On separate 60-second trials, participants were instructed to generate words beginning with the letters C, F, and L, excluding proper names and variants of the same word. Three scores were obtained for each pa rticipant: (1) number of words generated, excluding errors and repetitions; (2) mean cluster size; and (3) raw number of switches. Results: The patien ts showed small but significant impairments in clustering and larger impair ments in switching relative to normal controls. Conclusions: This pattern s uggests a relatively greater deficit in functioning in the frontal lobe tha n in the temporal lobe. However, neither measure was able to completely dis criminate patients with schizophrenia from controls. Moreover, differences in fluency performance were observed among subtypes of schizophrenia. Taken together, the findings of impaired performance for both aspects of fluency , differences between subtypes, and the failure to completely discriminate patients with schizophrenia from controls indicate that there is not a sing le marker of the disease, at least among these fluency variables. Instead, the current findings are more supportive of a multiple-disease model of sch izophrenia.