Sense of agency is altered in patients with a putative psychotic prodrome

Background: Sense of agency (SoAg) - the experience of controlling one's own actions and their consequences - has been studied in schizophrenia but not in the earlier stages of the disease, i.e. in patients with a putative psychotic prodrome (PP). Previous research has shown that time judgments of voluntary actions can provide an implicit measure of the SoAg. Method: 30 PP patients and 30 healthy controls performed voluntary key presses while watching a rotating clock hand on a monitor. After each key press they had to estimate the time of the action (based on the perceived position of the clock hand at the time of the key press). By varying the probability with which the simple manual action was followed by a tone, we investigated whether shifts in perceptual estimates of the operant action towards a resulting effect depended on the actual occurrence of the effect (retrospective process) or on the prediction that the effect will occur. Results: PP patients differed from healthy controls but their results did not resemble previous findings in schizophrenia patients. PP patients showed numerically - but not significantly - stronger temporal linkage between action and consequence than healthy controls. Retrospective and predictive influences on action binding were stronger in PP patients. Furthermore, the altered influence of prediction was significantly correlated to ego-psychopathology. Discussion: Distortions of agency constitute a core feature of the disease that is already present in the PP but may evolve further with progression of the illness. Distortions of agency may thus represent a promising additional predictive risk factor for transition to psychosis in PP patients. (C) 2010 Elsevier B.V. All rights reserved.