Optical illusion
Illusions and schizophrenia

Schizophrenia, a mental disorder often marked by hallucinations, also decreases a person's ability to perceive high-order optical illusions. This is because schizophrenia impairs one's capacity to perform top-down processing and a higher-level integration of visual information beyond the primary visual cortex, V1. Understanding how this specifically occurs in the brain may help in understanding how visual distortions, beyond imaginary hallucinations, affect schizophrenic patients. Additionally, evaluating the differences between how schizophrenic patients and unaffected individuals see illusions may enable researchers to better identify where specific illusions are processed in the visual streams.

One study on schizophrenic patients found that they were extremely unlikely to be fooled by a three dimensional optical illusion, the hollow face illusion, unlike neurotypical volunteers. Based on fMRI data, researchers concluded that this resulted from a disconnection between their systems for bottom-up processing of visual cues and top-down interpretations of those cues in the parietal cortex. In another study on the motion-induced blindness (MIB) illusion (pictured right), schizophrenic patients continued to perceive stationary visual targets even when observing distracting motion stimuli, unlike neurotypical controls, who experienced motion induced blindness. The schizophrenic test subjects demonstrated impaired cognitive organization, meaning they were less able to coordinate their processing of motion cues and stationary image cues.
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