• Reduced transfer of visuomotor adaptation is associated with aberrant sense of agency in schizophrenia

      Bansal, S.; Murthy, K.G.; Fitzgerald, J. (Elsevier Ltd, 2019)
      One deficit associated with schizophrenia (SZ) is the reduced ability to distinguish self-caused sensations from those due to external sources. This reduced sense of agency (SoA, subjective awareness of control over one's actions) is hypothesized to result from a diminished utilization of internal monitoring signals of self-movement (i.e., efference copy) which subsequently impairs forming and utilizing sensory prediction errors (differences between the predicted and actual sensory consequences resulting from movement). Another important function of these internal monitoring signals is the facilitation of higher-order mechanisms related to motor learning and control. Current predictive-coding models of adaptation postulate that the sensory consequences of motor commands are predicted based on internal action-related information, and that ownership and control of motor behavior is modified in various contexts based on predictive processing. Here, we investigated the connections between SoA and motor adaptation. Schizophrenia patients (SZP, N = 30) and non-psychiatric control subjects (HC, N = 31) adapted to altered movement visual feedback and applied the motor recalibration to untested contexts (i.e., the spatial generalization). Although adaptation was similar for SZP and controls, the extent of generalization was significantly less for SZP; movement trajectories made by patients to the furthest untrained target (135o) before and after adaptation were largely indistinguishable. Interestingly, deficits in generalization were correlated with positive symptoms of psychosis in SZP (e.g., hallucinations). Generalization was also associated with measures of SoA across both SZP and HC, emphasizing the role action awareness plays in motor behavior, and suggesting that misattributing agency, even in HC, manifests in abnormal motor performance. Copyright 2019 The Author(s)