Local versus global and retinotopic versus non-retinotopic motion processing in schizophrenia patients.

Schizophrenia impairs cognitive functions as much as perception. For example, patients perceive global motion in random dot kinematograms less strongly, because, as it is argued, the integration of the dots into a single Gestalt is complex and therefore deteriorated. Similarly, the perception of apparent motion is impaired, because filling-in of the illusory trajectory requires complex processing. Here, we investigated very complex motion processing using the Ternus-Pikler display. First, we tested whether the perception of global apparent motion is impaired in schizophrenia patients compared to healthy controls. The task requires both the grouping of multiple elements into a coherent Gestalt and the filling-in of its illusory motion trajectory. Second, we tested the perception of rotation in the same stimulus, which in addition requires the computation of non-retinotopic motion. Contrary to earlier studies, patients were not impaired in either task and even tended to perform better than controls. The results suggest that complex visual processing itself is not impaired in schizophrenia patients.