Simple and complex motor processing in chronic tic disorders

The hypotheses that tic disorded subjects would show greater difficulty than normal controls in initiating complex actions and suppressing automated/ballistic movements were tested using a 'countermanding paradigm'. Eleven tic subjects recruited prior to a cognitive-behaviroal tic management program, and eleven age, sex, and scholatically matched neuropsychiatrically screened nontic normal controls, were administered who replications of 52 trials of a computerized 'traffic light' test. In this test a series of three traffic lights indicated ready-go or ready-go-stop for either a complex controlled or automated response sequence. GO time and STOP time were measured over four conditions presented in random sequence (ready-go [complex]), ready-go [simple]), ready-go-stop [complex]) ready-go-stop [simple]). Results indicated that tic subjects took longer than controls to inhibit both complex and automated responses, but whereas the control subjects showed slower GO reaction times for the complex response, the tic subjects showed no difference between conditions. The tic subjects also showed no practice effects over replications. The results support an elevated level of motor activation in the tic group and a difficulty, for this group, to inhibit but not to initiate and execute an action.