SIMPLE MOTOR TICS MAY BE PRECEDED BY A PREMOTOR POTENTIAL

Obese st al reported that simple motor ties in Tourette's syndrome wer e not associated with premotor potentials, which were present when pat ients mimicked their ties voluntarily, suggesting that spontaneous tie s were not generated in the same manner as voluntary movements. Five p atients with simple motor ties were studied using a similar paradigm. Premotor potentials were examined during spontaneous ties and during v oluntary imitation of the tics. All patients had premotor negativity w ith the voluntary movements. As in the study of Obese et al, spontaneo us ties were not preceded by premotor potentials in three patients. Ho wever, premotor negativity was present with spontaneous ties in two pa tients and resembled the NS' segment of the premotor potential seen wi th self paced, voluntary movements. A similar premotor potential patte rn has been reported with voluntary movements performed in response to external triggering stimuli. In patients with Tourette's syndrome, th e eliciting signals could be internal sensations.