Oculomotor Dysfunctions

At the turn of the century, two researchers working in a psychiatric hospital in New England made the observation that patients with dementia praecox (now termed schizophrenia) had difficulty following an oscillating pendulum with their eyes. The investigation of eye movement dysfunction in schizophrenia, which was revived in the 1970s, focuses on smooth pursuit and saccadic eye movement systems.

Smooth eye pursuit, which is evoked by slow-moving objects such as a swinging pendulum, is significantly impaired in schizophrenia patients. As mentioned above, PET scans show that schizophrenia patients with smooth eye pursuit impairments do not activate the frontal eye fields, the cortical region involved in initiating these eye movements (Ross et al., 1995; O'Driscoll et al., 1998). Patients with schizophrenia are also deficient in their ability to inhibit reflexive saccadic eye movements, which are high-velocity movements that shift the eyes from one position to the other. Interestingly, eye movement dysfunctions are also present in the clinically unaffected relatives of patients with schizophrenia (Calkins and Iacono, 2000). These findings suggest that eye movement dysfunction is clearly an inheritable vulnerability trait that is not sufficient to cause schizophrenia but may be important in the search for schizophrenia susceptibility genes.

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