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Early expression of smooth-pursuit eye movement abnormalities in children of schizophrenic parents
1University of Colorado Health Sciences Center, Denver, USA. randy.ross@uchsc.edu
Insights
Children of parents with schizophrenia show abnormal eye movements, specifically frequent anticipatory saccades. This oculomotor dysfunction may indicate a genetic risk for schizophrenia years before illness onset.
Area of Science:
- Neuroscience
- Psychiatry
- Genetics
Background:
- Disordered smooth-pursuit eye movements (SPEM) and anticipatory saccades are hypothesized markers of genetic vulnerability to schizophrenia.
- Investigating SPEM in at-risk children may reveal early indicators of this vulnerability.
Purpose of the Study:
- To compare SPEM in children of schizophrenic parents with controls.
- To determine if SPEM abnormalities, particularly anticipatory saccades, are present in at-risk children.
Main Methods:
- Infrared oculography used to examine SPEM in 13 children of schizophrenic parents and 19 controls (aged 6-15).
- Measured smooth-pursuit gain, root mean square error, catch-up saccades, and anticipatory saccades.
Main Results:
- Children of schizophrenic parents showed differences in gain and root mean square error compared to controls.
- Significantly more frequent small anticipatory saccades were observed in the at-risk group.
- 54% of at-risk children exhibited excessive anticipatory saccades, unlike the control group.
Conclusions:
- Increased anticipatory saccades suggest oculomotor dysfunction.
- This dysfunction may represent a phenotype of genetic risk for schizophrenia.
- These abnormalities can be present years before clinical illness development.
Objective:
Disordered smooth-pursuit eye movements (SPEM) and, specifically, small anticipatory saccades that disrupt SPEM have been hypothesized to be a marker of genetic vulnerability to schizophrenia. This study compares SPEM in children of schizophrenic parents with normally developing control children to assess whether SPEM abnormalities are also present in a subset of at-risk children.
Method:
With infrared oculography, SPEM was examined in 13 children of schizophrenic parents and 19 normally developing controls (aged 6 to 15 years). Measures of smooth-pursuit gain and root mean square error were used in addition to more specific measures of catch-up saccades and anticipatory saccades.
Results:
Children of schizophrenic parents differed from normally developing controls on gain and root mean square error, but not on catch-up saccades. Small anticipatory saccades were significantly more frequent in the at-risk group. The percentage of total eye movements due to anticipatory saccades identified 54% of the at-risk group (compared with none of the control group) as performing more than two standard deviations above (worse than) the control mean.
Conclusions:
The presence of increased anticipatory saccades is evidence for an oculomotor dysfunction that may be a phenotype of the genetic risk for schizophrenia, expressed years prior to the possible development of clinical illness.