Heterogeneity of auditory verbal working memory in schizophrenia

Gerard E. Bruder, Daniel M. Alschuler, Christopher J. Kroppmann, Shiva Fekri, Roberto Gil, Lars F. Jarskog, Jill M. Harkavy-Friedman, Raymond Goetz, Jürgen Kayser, Bruce E. Wexler

Department of Psychiatry (GEB, RG, LFJ, JMH, JK), College of Physicians and Surgeons of Columbia University, and Division of Cognitive Neuroscience (GEB, DMA, CJK, SF, JK), New York State Psychiatric Institute, New York, New York, USA, and Department of Psychiatry (BEW), Yale University, New Haven, USA

Received 20 January 2010; revised 6 August 2010; accepted 17 August 2010; published online 10 January 2011. 

Abstract

The heterogeneity of schizophrenia remains an obstacle for understanding its pathophysiology. Studies using a tone discrimination screening test to classify patients have found evidence for two subgroups having either a specific deficit in verbal working memory (WM) or deficits on both verbal and nonverbal memory tests. This study aimed to: (1) replicate in larger samples differences between these subgroups on the word serial position test (WSPT); (2) further evaluate their performance on additional tests of verbal WM, explicit memory, and sustained attention; (3) determine the relation of verbal WM deficits to auditory hallucinations and other symptoms; and (4) examine medication effects. WSPT of verbal WM and tone discrimination performance did not differ between medicated (n = 45) and unmedicated (n = 38) patients. Patients with schizophrenia who passed the auditory screening test (discriminators, n = 60) were compared to those who did not (nondiscriminators, n = 23), and healthy controls (n = 47). The discriminator subgroup showed poorer verbal WM than controls and a deficit in verbal but not visual memory on Wechsler Memory Scale-Revised, whereas the nondiscriminator subgroup showed overall poorer performance on both verbal and nonverbal tests and a marked deficit in sustained attention. Verbal WM deficits in discriminators on WSPT were correlated with auditory hallucinations but not with negative symptoms. The results are consistent with a verbal memory deficit in a subgroup of schizophrenia having intact auditory perception, which may stem from dysfunction of language-related cortical regions, and a more generalized cognitive deficit in a subgroup having auditory perceptual and attentional dysfunction.

Key Words: schizophrenia, working memory, auditory perception, attention, hallucinations