Self and time in individuals with schizophrenia: A motor component?

Phenomenology suggests a disruption in the experience of time in individuals with schizophrenia, related to disorders of the sense of self. Patients themselves relate a fragmentation of their temporal experience and of their sense of self. Temporal expectations help relate the present moment to the future and we have previously shown that temporal expectations are fragile in patients, and relate to disorders of the self. Here, we investigate whether patients' performance is still impaired when the motor response to the expected event can be prepared in advance. In two different experiments participants (41 patients vs. 43 neurotypicals in total) responded to a visual target occurring at a variable interval (or "foreperiod") after an initial warning signal. Moreover, in Experiment 1 we measured the sense of self with the EASE scale. We observed the usual benefit of the passage of time: the longer the waiting period, the better the preparation, and the faster the responses. However, this effect also comprises sequential (surprise) effects, when a target occurs earlier than on the preceding trial. We evaluated the effect of the passage of time, by isolating trials that followed a trial with the same foreperiod. The benefit of long, versus short, foreperiods was still observed in controls but disappeared in patients. The results suggest that the benefit of the passage of time is diminished in patients and relates to self disorders, even when the task allows for motor preparation. The results suggest that a non-verbal impairment sub-tends disorders of the sense of self.