A neurophysiological deficit in early visual processing in schizophrenia patients with auditory hallucinations

Abstract

Existing 67-channel event-related potentials, obtained during recognition and working memory paradigms with words or faces, were used to examine early visual processing in schizophrenia patients prone to auditory hallucinations (AH, n = 26) or not (NH, n = 49) and healthy controls (HC, n = 46). Current source density (CSD) transforms revealed distinct, strongly left- (words) or right-lateralized (faces; N170) inferior-temporal N1 sinks (150 ms) in each group. N1 was quantified by temporal PCA of peak-adjusted CSDs. For words and faces in both paradigms, N1 was substantially reduced in AH compared with NH and HC, who did not differ from each other. The difference in N1 between AH and NH was not due to overall symptom severity or performance accuracy, with both groups showing comparable memory deficits. Our findings extend prior reports of reduced auditory N1 in AH, suggesting a broader early perceptual integration deficit that is not limited to the auditory modality.

Figure 1

Mean (±SEM) accuracy during recognition memory (RM) and working memory (WM) tasks using words or faces. Overall, remembering faces was more difficult than remembering words. Patients performed more poorly than healthy controls (HC), but auditory hallucinators (AH) did not differ significantly from nonhallucinators (NH), except for the word WM task. Significant contrasts between groups for each paradigm and each task are indicated as follows: * p ≤ .05; ** p ≤ .01; *** p ≤ .001.

Figure 2

N1 sink amplitude (adjusted for peak latency) for auditory hallucinators (AH), nonhallucinators (NH), and healthy controls (HC) during the recognition memory (RM) and working memory (WM) paradigms using words or faces. A. Grand mean current source density (CSD) [µV/cm²] waveforms at selected inferior lateral-parietal sites for words (left hemisphere sites P7, P9) and faces (right hemisphere sites P8, P10). These locations are highlighted in inset showing the 67-channel EEG montage (top view, nose up). B. Time courses of Varimax-rotated covariance loadings for PCA factors corresponding to N1 sink (RM: 141 ms peak latency; WM: 148 ms) and associated factor score topographies for each task and group. C. Mean (±SEM) N1 sink amplitude at inferior lateral-parietal sites (P7/8, P9/10) comparing AH, NH, and HC participants. Significant contrasts between groups for each paradigm, task, and hemisphere (LH: left; RH: right) are indicated as follows: (*) p ≤ .10; * p ≤ .05; ** p ≤ .01.