Abstract

Background: Studies using a tone screening test to classify patients have found evidence for schizophrenia subtypes having either verbal working memory (WM) or generalized cognitive deficits. Given the importance of defining schizophrenia subtypes having distinct cognitive and pathophysiological abnormalities, this study aimed to replicate these findings in larger samples, define symptom features of subtypes, and examine medication effects. Methods: Patients with schizophrenia who passed the screening test (discriminators, Dsz, n = 60) were compared to those who did not (nondiscriminators, NDsz, n = 23), and healthy controls (n = 52) on a verbal WM test (word serial position test, WSPT) and other neurocognitive tests. Results: Performance on the WSPT and tone screening test did not differ between medicated and unmedicated patients. Patients who performed as well as controls on the tone screening test (i.e., Dsz) showed poorer performance on the WSPT and a deficit in verbal but not visual memory on the Wechsler Memory Scale-Revised. In contrast, NDsz patients showed overall poor performance on both verbal and nonverbal tests, consistent with a generalized deficit. Verbal WM deficits in Dsz patients were significantly correlated with auditory hallucinations and positive thought disorder ratings, but not with negative symptoms of schizophrenia. As predicted, Dsz patients having auditory hallucinations showed poorer verbal WM than nonhallucinators and controls. Conclusions: These findings are consistent with neuroimaging findings suggesting that verbal WM deficits in Dsz patients stem from dysfunction of language-related regions in left inferior frontal and temporal cortex, and confirm the value of the tone screening test for parsing schizophrenia into cognitive subtypes.