Verbal fluency impairments among middle-aged and older outpatients with schizophrenia are characterized by deficient switching

Abstract

Patients with schizophrenia demonstrate impaired verbal fluency, but no studies have examined the underlying cognitive mechanisms (e.g., clustering and switching) associated with impaired fluency among middle-aged and older, non-institutionalized patients. Using Troyer et al.'s [Troyer, A.K., Moscovitch, M., Winocur, G., 1997. Clustering and switching as two components of verbal fluency: evidence from younger and older healthy adults. Neuropsychology 11 (1), 138–146] conceptual model, we examined clustering and switching on verbal fluency tasks among 163 middle-aged and older outpatients with schizophrenia and 92 age comparable healthy comparison (HC) participants. The patients produced significantly fewer total words than HC participants on both the letter (“F”, “A”, “S”) and Animal fluency conditions. With regard to clustering, patients were similar to HC participants on both FAS and Animal fluency tasks. However, significantly fewer switches between lexical–semantic categories were observed among patients with schizophrenia on both conditions relative to HC participants. A small, but statistically significant association was found between number of switches on the Animal fluency task and severity of negative symptoms. The absence of a difference in mean cluster size between the patient and HC groups suggests intact lexical–semantic stores among middle-aged and older outpatients with schizophrenia. Differences in switching between patients and HC participants may be driven by several cognitive impairments associated with schizophrenia. Further delineation of the cognitive mechanisms of the observed lexical–semantic switching deficits in schizophrenia should be a focus of future research.