Enhanced antisaccade abilities in children with Tourette syndrome: the Gap-effect Reversal

Tourette Syndrome (TS) is a childhood onset disorder of motor and vocal tics. The neural networks underlying TS overlap with those of saccade eye movements. Thus, deviations on saccadic tasks can provide important information about psychopathology of TS. Tourette syndrome often coexists with Attention Deficit Hyperactivity Disorder (ADHD) and Obsessive Compulsive Disorder (OCD). Hence, we manipulated various components of a saccade task to measure its effects on saccades of children with TS-only, TS+ADHD, TS+ADHD+OCD and healthy controls. Children looked toward (prosaccade) or in the opposite direction (antisaccade) of a peripheral target as soon as it appeared. The prosaccade and antisaccade tasks were presented in three conditions. In the Gap200 condition, the fixation dot disappeared 200 ms prior to the appearance of the peripheral target, In the Gap800 condition, the fixation dot disappeared 800 ms prior to the appearance of the peripheral target and in Overlap200 the fixation dot disappeared 200 ms after the appearance of the peripheral target. Fixation-offset manipulations had different effects on each group's antisaccades. The TS+ADHD+OCD group's antisaccade latencies and error rates remained relatively unchanged in the three conditions and displayed a pattern of eye movements that can be interpreted as enhanced. Alternatively, the TS+ADHD group displayed an overall pattern of longer saccadic latencies. Findings corroborate the hypothesis that the combination of tic disorder and ADHD results in unique behavioral profiles. It is plausible that a subgroup of children with TS develop an adaptive ability to control their tics which generalizes to enhanced volitional control of saccadic behavior as well. Supporting evidence and other findings are discussed.