M32. Impaired Time Prediction as a Mechanism for Agency and Body Ownership Disorders?

Abstract

Abstract Background: Recognizing one’s own actions and body requires a prediction of the state of the body, then checking whether this prediction has been fulfilled. These mechanisms have been suggested to be impaired in patients with schizophrenia. However, not all kinds of predictive mechanisms are impaired, and it remains to be understood how agency and body ownership disorders arise. We suggested recently that patients are impaired at predicting visual information over very short delays, thereby disrupting the continuity of sensory processing. We wondered whether such temporal impairments could impact the sense of self. Methods: We used a visual detection and a manual pointing task to explore both perceptual and motor prediction. In the visual task, a target occurred 400 or 1000 ms after a fixation point. Expectation of target onset automatically increases as time passes, resulting in shorter RTs (reaction times) at longer delays, indexing increasing temporal predictability. The manual task also explored expectation mechanisms, in this case expectation that sensory feedback would occur as a result of manually pointing on a surface. The use of a virtual device allowed us to manipulate the timing of sensory feedback (delayed by 0, 15 or 65 ms). Impact on the sense of self was explored with the EASE scale in the first task, and by asking subjects to evaluate their feeling of control after each series of manual pointing movements in the second task. Results: Results from both tasks showed that patients had normal sensory expectation to some extent: RTs decreased in the visual task when the target occurred after a delay of 1000 ms rather than 400 ms; patients also felt more in control when the sensory feedback resulting from their pointing action was not delayed. However, as soon as some uncertainty was introduced into the task, expectation and aspects of the sense of self were impaired. When the target appeared in only 75% of trials in the visual task, RTs actually increased, rather than decreased, for delays of 1000 ms vs 400ms. Moreover, the RT difference between 1000 ms vs 400 ms significantly correlated with the minimal self, as evaluated by the EASE, even when the target appeared in 100% of the trials. In the motor task, patients’ feeling of control dropped when there was a 15 ms delay in the sensory feedback, which did not occur in controls. Conclusion: Together, these results suggest that although patients can predict sensory information in time to some extent, they cannot cope with deviations from this prediction. The results suggest a vulnerability related to temporal prediction that may be involved in agency and body ownership disorders.