On one view, intention

to act is a perception-like experience that occurs when activity within frontal motor networks exceeds a threshold level (Fried et al., 2011, Hallett, 2007 and Matsuhashi and Hallett, 2008). On this view, the increased level of “motor noise” in GTS might require a more conservative threshold for detecting volition, in order to avoid excessive sensitivity to noise. This increased threshold would in turn produce delays in the perceived urge to move (Hallett, 2007) (see Fig. 1). This view therefore predicts that tic parameters should correlate with mean W judgement. Studies of developmental tic disorders could therefore selleck inhibitor potentially clarify the processes whereby voluntary control emerges from the wider noise of involuntary sensorimotor activity, and becomes a characteristic cognitive and phenomenological event. In particular, we speculated that the experience of volition in GTS could resemble a perception-like signal Paclitaxel clinical trial detection process, rather than a post hoc explanation of actions. Investigating this hypothesis would also provide an important

window into the learning process assumed to underlie the normal development of capacity for voluntary action. We therefore tested the experience of volition in 27 adolescents with GTS, and 30 healthy volunteers, using a cross-sectional design. We hypothesised that high levels of tics would be associated with delays in the normal experience of volition, because the characteristic neural activities that signal

one’s own volition would be lost in motor noise, delaying awareness of one’s own intentions. As a control for non-specific features of the task unrelated to volition, patients and controls also judged the perceived time of the keypress action itself. Twenty-seven adolescents (21 male) diagnosed with GTS aged between 10 and 17 years (mean age 13.7 years ± 2.3 SD) were recruited from the GTS outpatient clinic in the Department of Neurology, University Medical Center Hamburg-Eppendorf (clinical characteristics given in Supplementary Table 1). In two cases we were unable to collect scores on all clinical tests, so only 25 patients could be included in correlation analyses. The control group comprised 30 age-matched healthy control subjects (16 male, mean age 13 years ± 2.2 SD; range 10–17). All subjects and their parents gave their written informed consent those prior to study participation. The study was performed in accordance with the Declaration of Helsinki and was approved by the local ethics committee (PV4049). All subjects underwent a thorough clinical assessment (A.M., C.G.) based on a semi-structured neuropsychiatric interview adapted from Robertson and Eapen (Robertson & Eapen, 1996). DSM-IV-TR criteria were used for a diagnosis of GTS (American Psychiatric Association, 2000). Tic severity was determined using the Yale Global Tic Severity Scale (YGTSS) (Leckman et al., 1989) and the Modified Rush Video Scale (MRVS) (Goetz, Pappert, Louis, Raman, & Leurgans, 1999).