Altered use of extraretinal information during sequential saccadic eye movements among people with schizophrenia and bipolar disorder with psychotic features

Background: Impaired corollary discharge (CD) signalling disrupts the ability to predict the sensory consequences of one's own actions; impaired CD signalling may be specific to schizophrenia or it may also be a transdiagnostic mechanism of psychosis. We sought to assess whether disruptions in oculomotor CD signalling are equally present in schizophrenia and bipolar disorder (BD) with psychotic features, and whether these putative CD disruptions relate to anomalous self-experiences. Methods: We recruited patients with schizophrenia and patients with BD with psychotic features, as well as healthy controls, to complete a double-step saccade task. On each trial, 2 visual targets (T1 and T2) flashed in rapid succession. For half of the trials, participants could use visual information to look at T2. For the other half, looking correctly at T2 required CD. Results: We included 66 patients with schizophrenia, 43 patients with BD with psychotic features, and 37 healthy controls. On trials requiring CD, patient groups were significantly less accurate than controls in localizing T2 (F-2,F-131 = 8.40, p < 0.001). This reduced accuracy was related to difficulty in compensating for variability in the first saccade (F-2,F-131 = 9.11, p < 0.001). Among controls, anomalous self-experiences predicted worse performance (F-1,F- 57 = 14.23, p < 0.001). Limitations: Our sample comprised stable outpatients with relatively low symptom scores, which may limit the generalizability of our results. Conclusion: These results suggest CD impairments may be a marker of predisposition for psychosis. However, observed inconsistencies suggest that this relationship is nuanced.