Sensory and Cognitive Predictions, and Their Disruptions in Schizophrenia

In the task, two squares move at constant speed in a straight line towards each other. When they collide and disappear neurotypical individuals perceive a gap between the two squares rather than contact. This unexpected effect cannot be explained by a 'cognitive' expectation, since what is consciously expected is collision and contact. It has been shown that it is sensory predictions which explain the illusion of space at the moment of contact. Indeed, a movement trajectory is accompanied by sensory predictions, which help to anticipate the position of the moving object, and of the contrast between the edges of the squares and the background. At the moment of collision, the contrast disappears and is processed as a prediction error. If subjects do not have time to correct the error, they see a gap, as if the figure-ground contrast was still there. Conversely, when a rebound effect is introduced into the task (the squares are moved in the opposite direction after the collision), the illusion diminishes, as if the rebound reinforces the (top-down) expectation of a collision.

Perturbations will be introduced during the trajectory in the illusion task with and without rebound to test this hypothesis (acceleration on a millisecond scale vs. uniform speed). Patients suffering from schizophrenia, whose prediction mechanisms are fragile, are expected to be abnormally sensitive to trajectory changes. The experimental manipulations will help to compare sensory prediction (illusion without rebound) and top-down (conscious) prediction (illusion with rebound).

The protocol will also help to specify which types of prediction (sensory or cognitive) underlie patients' sense patients' sense of self. In short, the protocol is designed to improve the pathophysiological understanding of sense-of-self disorders in schizophrenia

Inclusion criteria

• Male or female;
• Age between 18 and 60 inclusive;
• Subject having dated and signed the consent form prior to the start of any trial-related procedure (guardian or curator where applicable);
• Member of a social security scheme or beneficiary of such a scheme.

Exclusion criteria

• Psychoactive substance use disorders (as defined by the DSM-V) (Diagnostic and Statistical Manual-V);
• Use of benzodiazepines, hallucinogens (in the period preceding before inclusion, for a duration equivalent to 5 half-lives of the product) or cannabis (in the 2 months preceding inclusion);
• Neurological pathology or sequelae;
• Attention deficit hyperactivity disorder (ADHD);
• Borderline personality disorder;
• Disabling sensory disorders (visual acuity <0.8);
• Person deprived of liberty or under court protection;
• Pregnant, parturient or breast-feeding women;
• Subjects in a period of exclusion defined by another clinical study.