Current Source Density (CSD) Old/New Effects During Recognition Memory for Words and Faces in Schizophrenia and in Healthy Adults

Jürgen Kayser^1,2, Craig E. Tenke^1,2, Christopher J. Kroppmann², Shiva Fekri², Daniel M. Alschuler², Nathan A. Gates²Roberto Gil¹, Jill M. Harkavy-Friedman¹, Lars F. Jarskog¹, Gerard E. Bruder^1,2

¹Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY, USA; ²Division of Cognitive Neuroscience, New York State Psychiatric Institute, New York, NY, USA

Received 21 August 2009; revised 25 November 2009; accepted 28 November 2009. Available online 6 December 2009. 

Abstract

We previously reported a preserved ?old-new effect? (enhanced parietal positivity 300-800 ms following correctly-recognized repeated words) in schizophrenia over mid-parietal sites using 31-channel nose-referenced event-related potentials (ERP) and reference-free current source densities (CSD). However, patients showed poorer word recognition memory and reduced left lateral-parietal P3 sources. The present study investigated whether these abnormalities are specific to words. High-density ERPs (67 channels) were recorded from 57 schizophrenic (24 female) and 44 healthy (26 female) right-handed adults during parallel visual continuous recognition memory tasks using common words or unknown faces. To identify and measure neuronal generator patterns underlying ERPs, unrestricted Varimax-PCA was performed using CSD estimates (spherical spline surface Laplacian). Two late source factors peaking at 442 ms (lateral parietal maximum) and 723 ms (centroparietal maximum) accounted for most of the variance between 250 and 850 ms. Poorer (76.6±20.0% vs. 85.7±12.4% correct) and slower (824±170 vs. 755±147 ms) performance in patients was accompanied by reduced stimulus-locked parietal sources. However, both controls and patients showed mid-frontal (442 ms) and left parietal (723 ms) old/new effects in both tasks. Whereas mid-frontal old/new effects were comparable across groups and tasks, later left parietal old/new effects were markedly reduced in patients over lateral temporoparietal but not mid-parietal sites, particularly for words, implicating impaired phonological processing. In agreement with prior results, ERP correlates of recognition memory deficits in schizophrenia suggest functional impairments of lateral posterior cortex (stimulus representation) associated with conscious recollection. This deficit was more pronounced for common words despite a greater difficulty to recall unknown faces, indicating that it is not due to a generalized cognitive deficit in schizophrenia.

Key Words: Event-related potentials (ERP); Current source density (CSD); Principal components analysis (PCA); Schizophrenia; Recognition memory; Old/new effect; Words; Faces