ERP Generator Patterns in Schizophrenia during Tonal and Phonetic Oddball Tasks: Effects of Response Hand and Silent Count

Abstract

Greater left than right reductions of P3 amplitude in schizophrenia during auditory oddball tasks have been interpreted as evidence of left-lateralized dysfunction. However, the contributions of methodological factors (response mode, stimulus properties, recording reference), which affect event-related potential (ERP) topographies, remain unclear. We recorded 31-channel ERPs from 23 schizophrenic patients and 23 age- and gender-matched healthy controls (all right-handed) during tonal and phonetic oddball tasks, varying response mode (left press, right press, silent count) within subjects. Performance accuracy was high in both groups but patients were slower. ERP generator patterns were summarized by temporal Principal Components Analysis (PCA; unrestricted Varimax) from reference-free current source density (CSD; spherical spline Laplacians) waveforms, which sharpen scalp topographies. CSD represents the magnitude of the radial current flow entering (source) and leaving (sink) the scalp. Both patients and controls showed asymmetric frontolateral and parietotemporal N2 sinks peaking at 240 ms and asymmetric parietal P3 sources (355 ms) for targets (tonal R > L, phonetic L > R), but frontocentral N2 sinks and parietal P3 sources were bilaterally reduced in patients. A response-related midfrontal sink and accompanying centroparietal source (560 ms) were highly comparable across groups. However, a superimposed left temporal source was larger for silent count compared to button press, and this difference was smaller in patients. In both groups, left or right press produced opposite, region-specific asymmetries originating from central sites, modulating the N2/P3 complex. The results suggest bilaterally reduced neural generators of N2 and P3 in schizophrenia during auditory oddball tasks, but both groups showed comparable topographic effects of task and response mode. However, additional working memory demands during silent count may partially overlap in time the generation of the N2/P3 complex and differentially affect the asymmetry of P3 subcomponents, particularly when employing conventional ERP measures.

Exploring the dynamics of P300 amplitude in patients with schizophrenia

“…However, some other studies that relied on similar protocols did report lower P300 amplitudes on patients with schizophrenia (e.g. Kayser et al, 2010;Kim et al, 2003). Further, Ford et al (2000) studied the effect of the type of task (button press vs. count) on the reduction and symmetry of P300 in schizophrenia, reporting no effects or interactions relating to the type of task.…”

The use of current source density as electrophysiological correlates in neuropsychiatric disorders: A review of human studies

“…Furthermore, methodological improvements for the CSD techniques have been very rare and slow. One obvious exception to this limitation is the work by Kayser, Tenke and Colleagues, who have innovated some methods, for example, to extract PCA components of the CSD (Kayser and Tenke, 2003; Tenke and Kayser, 2005) and successfully implemented this approach to study clinical domains (Kayser et al, 2006, 2009, 2010a,b,c, 2012, 2013, 2014; Tenke et al, 2008, 2010, 2011). Other concerns of CSD are related to its methodological limitations, which may be addressed by future studies: 1) the transformation of the EEG potentials into the CSD leads to a partial data loss, since the low-spatial-frequency (LSF) components are attenuated (Hjorth, 1980; cf.…”

“…In order to unravel the subprocesses of verbal working memory deficits in schizophrenia, Kayser et al (2006) used the CSD method in a visual word serial position task and found that schizophrenic patients showed reduced left inferior parieto-temporal P3 sources. Using tonal and phonetic oddball tasks, Kayser et al (2010a) studied ERP generator patterns as elicited by temporal PCA to examine the earlier findings showing left-lateralized dysfunction in schizophrenics with greater left than right reductions of P3 amplitude, and found a bilateral reduction in fronto-central N2 sinks and parietal P3 sources. In another study, using visual continuous recognition memory tasks with common words or unknown faces, Kayser et al (2010b) investigated whether the visual recognition memory deficits in schizophrenics were restricted to only words.…”

Auditory event-related potentials and alpha oscillations in the psychosis prodrome: Neuronal generator patterns during a novelty oddball task

“…The distinct FRN topography, consisting of its defining mid-frontal sink (negativity) accompanied by off-midline centroparietal sources (positivity), has been observed as a stimulus- as well as a response-locked CSD component across a variety of visual and auditory ERP paradigms, including tonal and phonetic oddball tasks (e.g., Kayser and Tenke, 2006a, 2006b, Kayser et al, 2010a), dichotic oddball (Tenke et al, 2008), novelty oddball (Tenke et al, 2010), and recognition memory (Kayser et al, 2007, 2010b), and interpreted as an index of ongoing motivational or action-monitoring processes. Importantly, the centroparietal source is impacted by the response requirements, being asymmetric for left or right hand responses (i.e., larger over the ipsilateral hemisphere; cf.…”