Visual and Auditory Event-Related Potential (ERP) Correlates of Continuous Word Recognition Memory (RM) in Schizophrenia

Jürgen Kayser¹, Gerard E. Bruder¹, Craig E. Tenke¹, Roberto Gil¹, Jack M. Gorman²

¹New York State Psychiatric Institute, New York, USA; ²Mount Sinai School of Medicine, New York, USA

Abstract

In a visual continuous word RM task, a prior study reported a preserved ERP ‘old-new effect' (enhanced medial-posterior positivity between 300 and 800 ms for correctly recognized repeated items) in schizophrenia. However, patients showed reduced early negative potentials (N1, N2) and poorer recognition accuracy. To study the impact of modality, 30-channel nose-referenced EEGs were recorded from 16 schizophrenic patients and 26 healthy controls in visual and auditory word RM tasks (excluding subjects performing close to chance). Spatially and temporally overlapping ERP components were measured by unrestricted, Varimax- rotated, covariance-based principal components analysis. Patients performed more poorly than controls in both modalities and showed reduced N1 and particularly N2 for both visual (p=.002) and auditory (p<.001) stimuli. The topography of N2 reduction in patients was modality-specific, most marked at medial-central (auditory) and posterior sites (visual), suggesting that the functional classification process underlying N2 amplitude is impaired in schizophrenia. Both patients (p=.002) and controls (p<.001) showed a robust auditory ‘old-new effect,' overlapping the N2/P3 transition. In the visual modality, an ‘old-new effect' was superimposed on P3 in controls (p=.01), but not in patients. However, surface Laplacians and rereferenced ERPs (linked mastoids) revealed an ‘old-new effect' for patients and controls in both modalities. Results replicate our prior findings in schizophrenia for word RM, and indicate that they extend to the auditory modality.

Keywords: ERP, recognition memory, schizophrenia