Experimental studies in monkeys have demonstrated that injection of gamma-aminobutyric acid (GABA) agonists into the superior colliculus restricts saccadic eye movements, while injection of GABA antagonists leads to square-wave jerks (SWJ). To investigate the role of GABA in saccadic interruptions of fixation, we treated five patients who had SWJ and square-wave oscillations (SWO) with valproic acid (VPA) (2000 mg/d), which has been shown to increase brain GABA levels. VPA effectively reduced the SWJ/SWO in three patients, abolished them in one patient, but was ineffective in the fifth, who had a localized lesion in the cerebellar vermis. VPA effects may have been due to the restoration of the GABAergic tonic inhibitory action from the substantia nigra pars reticulata to the superior colliculus.

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