Sensory and Cognitive Predictions, and Their Disruptions in Schizophrenia

Overview

Disturbances in the sense of self and time could play an important role in the development of psychotic symptoms. Previous work has shown that patients have difficulty preparing to process information on the scale of a second, but are abnormally disturbed by slightly asynchronous information on the millisecond scale. In both cases, the anomalies could explain the patients' unusual experience of time. The hypothesis in neurotypical patients is that small delays or asynchronies asynchronies are treated as irrelevant information and ignored and ignored, whereas in patients suffering from schizophrenia they would disrupt the flow of time. This hypothesis is tested with a new visual illusion.

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