Anticipatory grip adjustments are observed in both goal-directed movementsand movement tics in an individual with Tourette's syndrome

We examined grip force adjustments during movements of a hand-held object i n a young man (BF) with Tourette's syndrome. We directly compared BF's volu ntary up and down movements with ties in the same directions. Movement ties were elicited by cueing BF to move either up or down on a GO signal which appeared after a variable delay. During the delay period, we observed frequ ent ties which were almost always in the cued movement direction. BF's volu ntary movements were well coordinated and featured precise and appropriate anticipatory grip force adjustments such that grip force was modulated in p hase with movement-induced fluctuations in load. Precise anticipatory grip force adjustments were also observed in all of BF's movement ties. These re sults support the hypothesis that ties in Tourette's syndrome are purposefu l voluntary movements that are well organized and coordinated.