Simple and complex motor processing in chronic tic disorders

The hypotheses that tic disorded subjects would show greater difficulty tha n normal controls in initiating complex actions and suppressing automated/b allistic movements were tested using a "countermanding paradigm." Eleven tic subjects recruited prior to a cognitive-behavioral tic managemen t program, and eleven age, sex, and scholastically matched neuropsychiatric ally screened nontic normal controls, were administered two 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 comp lex controlled or automated response sequence. GO time and STOP time were m easured over four conditions presented in random sequence (ready-go [comple x]), ready-go [simple]), ready-go-stop [complex]) ready-go-stop [simple]). Results indicated that tic subjects took longer than controls to inhibit bo th 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 bu t not to initiate and execute an action. (C) 1999 Academic Press.