Eye-tracking dysfunction has been found in many patients with schizophrenia and in about 40% of their first-degree biological relatives. We hypothesized that a deficit in motion processing is associated with eye-tracking dysfunction because both motion signals and the brain regions responsible for processing motion signals are implicated in the generation of smooth pursuit. We examined several aspects of visual perception, including motion perception, in patients with schizophrenia.
To evaluate motion perception, contrast sensitivity for velocity discrimination was measured in patients with schizophrenia (n=15) and normal control subjects (n=18). Contrast sensitivities for orientation discrimination and contrast detection were measured as control tasks.
Patients with schizophrenia showed significantly lower contrast sensitivity (ie, higher thresholds) than normal controls for the discrimination of small velocity differences (eg, 11 vs 9 degrees/s). This reduction in contrast sensitivity was severe (up to 10-fold) in about 40% of the patients. No group differences were found on the other tasks.
The discrimination of small velocity differences is impaired in a subgroup of patients with schizophrenia.