Altered performance monitoring in Tourette Syndrome: an MEG investigation

The error-related negativity (ERN) is an event-related potential component indexing processes of performance monitoring during simple stimulus-response tasks: the ERN is typically enhanced for error processing and conflicting response representations. Investigations in healthy participants and different patient groups have linked the ERN to the dopamine system and to prefrontal information processing. As in patients with Tourette Syndrome (TS) both dopamine release and prefrontal information processing are impaired, we hypothesized that performance monitoring would be altered, which was investigated with magnetencephalography (MEG). We examined performance monitoring in TS patients by assessing the magnetic equivalent of the ERN (mERN). The mERN was investigated in tic-free trials of eight adult, unmedicated TS patients without clinically significant comorbidity and ten matched healthy controls while performing a Go/NoGo task in selected frontocentral channels. The analysis of the response-related amplitudes of the event-related magnetic field showed that TS patients, in contrast to controls, did not show earlier amplitude modulation (between 70 and 105 ms after response onset) depending on response type (errors or correct responses). In both groups significant mERN amplitudes in the time-window between 105 and 160 ms after response onset were detected thus pointing at only later error processing in TS patients. In TS patients, early error-related processing might be affected by an enhanced motor control triggered by a conflict between the targeted high task performance and tic suppression. TS patients seem to tend to initially process all responses as erroneous responses.