Predicting the sensory consequences of saccadic eye movements likely<br />plays a crucial role in planning sequences of saccades and in<br />maintaining visual stability despite saccade-caused retinal<br />displacements. Deficits in predictive activity, such as that afforded by<br />a corollary discharge signal, have been reported in patients with<br />schizophrenia, and may lead to the emergence of positive symptoms, in<br />particular delusions of control and auditory hallucinations. We examined<br />whether a measure of delusional thinking in the general, non-clinical<br />population correlated with measures of predictive activity in two<br />oculomotor tasks. The double-step task measured predictive activity in<br />motor control, and the in-flight displacement task measured predictive<br />activity in trans-saccadic visual perception. Forty-one healthy adults<br />performed both tasks and completed a questionnaire to assess delusional<br />thinking. The quantitative measure of predictive activity we obtained<br />correlated with the tendency towards delusional ideation, but only for<br />the motor task, and not the perceptual task: Individuals with higher<br />levels of delusional thinking showed less self-movement information use<br />in the motor task. Variation of the degree of self-generated movement<br />knowledge as a function of the prevalence of delusional ideation in the<br />normal population strongly supports the idea that corollary discharge<br />deficits measured in schizophrenic patients in previous researches are<br />not due to neuroleptic medication. We also propose that this difference<br />in results between the perceptual and the motor tasks may point to a<br />dissociation between corollary discharge for perception and corollary<br />discharge for action.
Malassis, R., Del Cul, A., & Collins, T. (2015). Corollary discharge failure in an oculomotor task is related to delusional ideation in healthy Individuals. PLoS ONE, 10(8). https://doi.org/10.1371/journal.pone.0134483