Impaired eye movements could play a part in the symptoms of schizophrenia, according to a study published in the Journal of Neuroscience.
Researchers form the University of British Columbia tracked the eye movements of patients with schizophrenia while they played a basic video game.
Schizophrenia is a mental illness most likely to appear in late adolescence or early adulthood. Symptoms of the disorder include loss of personality, delusions, agitation, confusion, social withdrawal, psychosis and bizarre behavior.
According to the World Health Organization (WHO), schizophrenia affects around 24 million people worldwide, and it is estimated that around 50% of those suffering from the disorder are not receiving appropriate care.
For the study, a group of schizophrenia patients, alongside a group of healthy patients, were asked to predict the trajectory of a small dot that briefly appeared on the screen as it moved toward a vertical line.
Participants were asked to follow a dot on a monitor while their eye movements were tracked
The participants were required to call out whether the dot would hit or miss the line, while an infrared-equipped video camera tracked their eye movements.
Results showed that the patients with schizophrenia found it harder to follow the moving dot and predict its movements, compared with healthy patients who did not have the disorder.
However, the researchers note that the impairment in the schizophrenic patients' eye movements were not bad enough to explain differences in their predictive performance.
They say this suggests there is a "broken connection" in the ability of schizophrenic patients to interpret what they see.
The researchers explain that the schizophrenic patients were finding it difficult to generate or use "efference copy." This is a signal that the eye movement area of the brain sends to determine in which direction and how much an eye has moved.
Lead study author Miriam Spiring believes schizophrenia patients can practice their "efferent copy" ability
Miriam Spering, assistant professor of ophthalmology and visual sciences at the university, explains: "An impaired ability to generate or interpret efference copies means the brain cannot correct an incomplete perception. The brain might fill in the blanks by extrapolating from prior experience, contributing to psychotic symptoms, such as hallucinations."
Spering adds that she believes schizophrenic patients could practice the ability to generate or use that efference copy:
"My vision would be a mobile device that patients could use to practice that skill, so they could more easily do common tasks that involve motion perception, such as walking along a crowded sidewalk."
Spering says that she is looking to carry out the same experiment with patients suffering from Parkinson's disease. She says that Parkinson's patients have poor visual perception and impaired movements in addition to muscle tremors and stiffness, and she would like to find out if the two are linked.
She adds that if this is the case, eye-movement exercises could improve vision in Parkinson's patients.