Self-attribution bias during continuous action-effect monitoring in patients with schizophrenia.

The feeling of being the source and controller of one's actions and their effects in the outside world is an important aspect of our sense of self. Disturbances in this sense of agency (SoA) were observed in schizophrenia and have been linked to impairments in sensorimotor integration. We used a virtual-world action-monitoring paradigm to investigate the SoA in 20 schizophrenic patients and 18 healthy subjects. Participants continuously moved a virtual pen displayed on a computer screen using a touchpad device. The control they exceeded over the virtual pen was switched periodically between the participant and the computer. Participants were requested to monitor their actions and the effects on the virtual pen, and indicate loss or regain of control over the pen's movement by button presses. The numbers of erroneous external attribution of action effects (false negative agency judgements) and erroneous self-attribution (false positive agency judgements) were not significantly different in patients and healthy subjects. However, patients showed a significant increase in the duration of false negative agency judgements. Moreover, the number of false negative agency judgements as well as the number and the duration of false positive agency judgements were negatively correlated with the performance in cognitive tests (BACS) in the patient group only. Our findings indicate that the evaluation system to detect a mismatch between actions and their effects in the outside world is probably more rigid in schizophrenic patients, which leads to an increased self-attribution bias for action effects, as commonly found in delusions of control. The impairment in sensorimotor integration may be compensated for by stronger cognitive control.