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Increased saccadic distractibility in tardive dyskinesia: functional evidence for subcortical GABA dysfunction
G K Thaker1, J A Nguyen, C A Tamminga
1Maryland Psychiatric Research Center, Department of Psychiatry, University of Maryland, Baltimore 21228.
Biological Psychiatry
|January 1, 1989
Summary
Schizophrenic patients exhibit increased saccadic distractibility and volitional saccade latency. Tardive dyskinesia exacerbates saccadic distractibility, suggesting basal ganglia GABA dysfunction in schizophrenia and TD.
Area of Science:
- Neuroscience
- Ophthalmology
- Psychiatry
Background:
- GABAergic projections from the substantia nigra reticulata to the superior colliculus regulate saccadic eye movements.
- Dysfunction in this pathway is linked to saccadic distractibility in animal models.
Purpose of the Study:
- To investigate saccadic eye movement control in chronic schizophrenic patients with and without tardive dyskinesia (TD).
- To explore potential basal ganglia GABA dysfunction in TD and schizophrenia.
Main Methods:
- Oculomotor paradigms were used to test saccadic eye movement control.
- Participants included chronic schizophrenic patients with TD (n=18), without TD (n=16), and normal controls (n=8).
- Groups were matched for age, illness duration, medication dosage, and education.
Main Results:
- Saccadic distractibility was twofold higher in TD patients compared to non-TD schizophrenic patients.
- Both schizophrenic groups showed greater saccadic distractibility than normal controls.
- Schizophrenic patients (with and without TD) exhibited significantly increased latency for volitional saccades.
Conclusions:
- Findings suggest basal ganglia GABA dysfunction in tardive dyskinesia.
- Oculomotor abnormalities, specifically saccadic distractibility and volitional saccade latency, are present in schizophrenic individuals.