EEG correlates of impaired self-other integration during joint-task performance in schizophrenia

Abstract

Deficits in a wide variety of social cognitive processes are well established in schizophrenia. However, research focusing on actual interacting individuals is surprisingly scarce. Problems in low-level processes such as self-other integration may importantly underlie often-reported higher-level deficits. The current study aimed at measuring possible disturbances in self-other integration in schizophrenia using both behavioral and event-related potential (ERP) measures. Sixteen healthy controls and fifteen schizophrenia patients performed a social Simon task in both a joint and an individual setting. Behaviorally, patients showed general slower reaction times, but comparable self-other integration as reflected in the social Simon effect. The ERP results for the healthy controls revealed increased no-go P3 amplitudes in the joint compared with the individual setting. Crucially, patients did not show this increase in no-go P3 amplitude. In line with previous research, the present ERP findings demonstrate that healthy volunteers needed more effort to inhibit their responses in the joint compared with the individual setting. Patients however, showed altered self-other integration when they had to withhold their responses while their co-actor had to act. These outcomes indicate that schizophrenia patients have deficits in low-level processes required for successful joint action.

Keywords: P3 ERP; joint action; schizophrenia; self-other integration; social Simon effect.

Fig. 1

Task setup of the social Simon task. The participant sitting on the right responds to the same color of the stimulus in both the individual (left) and the joint setting (right).

Fig. 2

Mean RT as a function of spatial stimulus-response compatibility per condition (individual, joint) and per group (patients, healthy controls). Error bars represent standard errors of the mean.

Fig. 3

Grand average stimulus-locked waveforms showing no-go P3 ERP amplitudes for the different compatibility conditions and different settings at electrode sites Fz and Cz for both healthy controls (left) and schizophrenia patients (right).

Fig. 4

Difference waveforms (joint minus solo condition) of the stimulus locked no-go P3 grand average for healthy controls (A) and schizophrenia patients (B) at electrode site Fz. Topographical distribution of the difference waves showing the frontocentral distribution for the maximal no-go P3 peak amplitude in healthy controls (C). Darker red colors indicate more positive amplitudes.