Preparation and motor potentials in chronic tic and Tourette syndromes

Many studies have found that people with tie disorder show more difficulty when inhibiting an automated than a controlled response. Furthermore. altho ugh normal motor threshold and excitability are present, but reduced or imp aired, motor inhibition seems manifest in patients with tie. In order to lo calize this inhibition impairment in tic disorder the present study examine two response-locked ERPs: the Bereitschaft (preparation BP) and the motor potentials (MP). The simple tie group showed faster BP latency and smaller amplitude than control and complex tic group and did not show a correspondi ng change in values with practice or with automated or controlled condition . The MP amplitudes revealed that whereas both controls and complex tie dis order showed a decrease in amplitude during control condition for both bloc ks, simple tic showed larger amplitude. Our ERP results are in agreement wi th RT results of a previous study. The explanation could lie with modulatio n in motor excitation inhibition circuits and seems worse in simple ties wh ere the movements are more automatic and nonvoluntary. (C) 2001 Academic Pr ess.