Altered inhibition of motor responses in Tourette Syndrome and Obsessive-Compulsive Disorder

Objectives - The Gilles de la Tourette Syndrome (TS) and Obsessive Compulsi ve Disorder (OCD) have been shown to display impaired cognitive and motor i nhibition. This study investigated inhibitory mechanisms of motor responses in order to expand the understanding of sensorimotor integration processes in both disorders. We hypothesized that both patient groups would display altered frontal inhibitory activity. Material and methods - To this end eve nt-related brain potentials (ERPs) were recorded in a STOP-paradigm in grou ps of TS and OCD patients and in a control group. The paradigm required the execution of a motor response after a "go" signal was given and the occasi onal suppression of this response after a second "stop" signal occurred. Re sults - Behavioral parameters and Lateralized Readiness Potential (LRP) con firmed that both patient groups were well able to initiate motor responses. "Go" and "stop" stimuli elicited an enhanced frontal negative activity in both patient groups. In addition, "stop" stimuli were associated with a fro ntal shift of the NoGo-Anteriorization (NGA) in the TS group but not in the OCD group. Conclusions - The data are interpreted to indicate altered fron tal inhibitory functions. Similarities and dissimilarities between the find ings for TS and OCD are discussed with respect to other pathophysiologic as pects of the disorders.