Antisaccade eye movement abnormalities in Tourette syndrome: evidence for cortico-striatal network dysfunction?

Saccadic eye movements are rapid eye movements which act to redirect the eyes from one object of interest to another. Accurately and objectively measurable, their underlying neuroanatomical mechanisms have been extensively studied. The antisaccade task allows the study of the frontocortico-striatal network involved in the voluntary control of saccadic eye movements. In this task, the subject is instructed to inhibit a reflex eye movement towards a peripheral target light and, instead, to generate a movement in the equal and opposite direction. An error occurs when the subject fails to suppress reflexive saccades towards the target. Significantly high error rates and increased latencies in the antisaccade task have been reported in disorders associated with dysfunction of the frontocortico-striatal network. Increased saccadic eye movement latencies and error rates have been reported in Tourette syndrome patients (n = 4) who were receiving antipsychotic medication. To investigate this further, we tested the antisaccade task on six male Tourette syndrome patients. The results were compared with 18 age- and sex-matched mentally and physically healthy, medication/alcohol-free controls. Antisaccade latenecies were (mean +/- SD; ms) 751.2 +/- 186.7 for the Tourette syndrome group and 417 +/- 75.3 for controls, and error rates were 59 +/- 14.3 for the Tourette syndrome group and 11.9 +/- 6.4 for controls, repectively. These significant results may further support dysfunction of the frontocortico-striatal network in Tourette syndrome.