07, p = .289]. We found no difference in the average time of conscious intention between GTS patients and controls in our group of adolescents. A previous study had reported a delay in conscious intention in adults with GTS relative to controls (Moretto et al., 2011) but this result was not replicated in our younger and larger sample. The absence of delay in adolescence combined with delayed experience of volition in adults with GTS suggests that adults may learn the experience of volition. In healthy adults, the normal experience of intention prior to voluntary action may Etoposide concentration reflect

prolonged perceptual learning at discriminating the internal signals that characterise volition. Persistent co-occurrence of voluntary and involuntary movement in GTS could make this discrimination problem harder. Therefore, patients with GTS may show delayed learning about their own volition, or may extinguish such learning after it has occurred, as a result of prolonged tic behaviour. Adults have prolonged experience of their own voluntary action, and may have learned the discriminative perceptual markers of volition. However, for an adult with GTS, frequent

MDV3100 ic50 tics may have made this discrimination harder, leading to a more conservative criterion for detecting the signal among noise. GTS adults may thus lack the normal anticipatory awareness of intentional action. In our adolescent sample, the two groups do not yet diverge in this way. That is, we suggest that the delayed experience of volition in adult GTS represents a failure of perceptual learning for volition-related signals, due to masking only by tics and tic-related factors, such as premonitory urges. Some possible factors are discussed in the next section. GTS is characterised by tics. Our results

showed several influences of ticcing on the experience of voluntary action. These results are consistent with the broad theory that the experience of volition involves learning a perceptual discrimination between the distinctive internal states and signals corresponding to preparation of voluntary actions, and other, involuntary body movements. For example, a striking result of our regression analysis was that subjective experiences linked to involuntary tic movements (measured by the PUTS) provided the single strongest predictor of volition. Participants who experienced strong premonitory urges prior to tics had a later perception of the intention preceding voluntary action. Stronger premonitory urges preceding involuntary movements could impair detection of the distinctive experience of volition, since urges to tic would constitute perceptual noise masking actual intentions.