Background: Currently, there is a marked increase of young people with sudden onset of tic-like behaviors (TLBs) resembling movements and vocalizations presented on social media videos as "Tourette's syndrome." Objective: To delineate clinical phenomenology of TLBs after social media exposure in comparison with clinical features of Tourette's syndrome. Methods: We compared demographic and clinical variables between 13 patients with TLBs and 13 ageand sex-related patients with Tourette's syndrome. Results: Patients with TLBs had several characteristics allowing to distinguish them from patients with Tourette's syndrome, some of which discriminated perfectly (ie, abrupt symptom onset, lack of spontaneous symptom fluctuations, symptom deterioration in the presence of others) and some nearly perfectly (ie, predominantly complex movements involving trunk/extremities). Also, symptom onset was significantly later. Conclusions: TLBs after social media consumption differ from tics in Tourette's syndrome, strongly suggesting that these phenomena are categorically different conditions.

Tourette syndrome is a common neurodevelopmental disorder defined by multiple motor and phonic tics. Tics in Tourette syndrome resemble spontaneously occurring movements in healthy controls and are therefore sometimes difficult to distinguish from these. Tics may in fact be mis-interpreted as a meaningful action, i.e. a signal with social content, whereas they lack such information and could be conceived a surplus of action or ‘motor noise’. These and other considerations have led to a ‘neural noise account’ of Tourette syndrome suggesting that the processing of neural noise and adaptation of the signal-to-noise ratio during information processing is relevant for the understanding of Tourette syndrome. So far, there is no direct evidence for this. Here, we tested the ‘neural noise account’ examining 1/ f noise, also called scale-free neural activity as well as aperiodic activity, in n = 74 children, adolescents and adults with Tourette syndrome and n = 74 healthy controls during task performance using EEG data recorded during a sensorimotor integration task. In keeping with results of a previous study in adults with Tourette syndrome, behavioural data confirmed that sensorimotor integration was also stronger in this larger Tourette syndrome cohort underscoring the relevance of perceptual-action processes in this disorder. More importantly, we show that 1/ f noise and aperiodic activity during sensorimotor processing is increased in patients with Tourette syndrome supporting the ‘neural noise account’. This implies that asynchronous/aperiodic neural activity during sensorimotor integration is stronger in patients with Tourette syndrome compared to healthy controls, which is probably related to abnormalities of GABAergic and dopaminergic transmission in these patients. Differences in 1/ f noise and aperiodic activity between patients with Tourette syndrome and healthy controls were driven by high-frequency oscillations and not lower-frequency activity currently discussed to be important in the pathophysiology of tics. This and the fact that Bayesian statistics showed that there is evidence for the absence of a correlation between neural noise and clinical measures of tics, suggest that increased 1/ f noise and aperiodic activity are not directly related to tics but rather represents a novel facet of Tourette syndrome.

Premonitory urges preceding tics are a cardinal feature of Gilles de la Tourette syndrome (GTS), a developmental disorder usually starting during middle childhood. However, the temporal relation between urges and tics has only been investigated in adults. In 25 children and adolescents with GTS (8–18 years), we assess urge-tic associations, including inter-individual differences, correlation to clinical measures, and in comparison to a previously reported sample of adult GTS patients. Group-level analyses confirmed positive associations between urges and tics. However, at the individual level, less than half of participants showed positive associations, a similar proportion did not, and in two participants, the association was reversed. Tic expression and subjective urge levels correlated with corresponding clinical scores and participants with more severe tics during the urge monitor exhibited stronger urge-tic associations. Associations between reported urge levels and instantaneous tic intensity tended to be less pronounced in children and adolescents than in adult GTS patients. The observed heterogeneity of urge-tic associations cast doubt on the notion that tics are directly caused by urges. More severe tics may facilitate anticipation of tics and thereby lead to more pronounced urge-tic associations, consistent with a hypothesis of urges as a byproduct of tics.

Tics in Tourette syndrome are often difficult to discern from single spontaneous movements or vocalizations in healthy people. In the present study, videos of patients with Tourette syndrome and healthy controls were taken and independently scored according to the Modified Rush Videotape Rating Scale. We included n = 101 patients with Tourette syndrome (71 males, 30 females, mean age 17.36 years ± 10.46 standard deviation) and n = 109 healthy controls (57 males, 52 females, mean age 17.62 years ± 8.78 standard deviation) in a machine learning-based analysis. The results showed that the severity of motor tics, but not vocal phenomena, is the best predictor to separate and classify patients with Tourette syndrome and healthy controls. This finding questions the validity of current diagnostic criteria for Tourette syndrome requiring the presence of both motor and vocal tics. In addition, the negligible importance of vocalizations has implications for medical practice, because current recommendations for Tourette syndrome probably also apply to the large group with chronic motor tic disorders.

Gilles de la Tourette syndrome (GTS) is a neuropsychiatric disorder. Because motor signs are the defining feature of GTS, addressing the neurophysiology of motor processes is central to understanding GTS. The integration of voluntary motor processes is subject to so-called “binding problems”, i.e., how different aspects of an action are integrated. This was conceptualized in the theory of event coding, in which ‘action files’ accomplish the integration of motor features. We examined the functional neuroanatomical architecture of EEG theta band activity related to action file processing in GTS patients and healthy controls. Whereas, in keeping with previous data, behavioral performance during action file processing did not differ between GTS and controls, underlying patterns of neural activity were profoundly different. Superior parietal regions (BA7) were predominantly engaged in healthy controls, but superior frontal regions (BA9, BA10) in GTS indicated that the processing of different motor feature codes was central for action file processing in healthy controls, whereas episodic processing was more relevant in GTS. The data suggests a cascade of cognitive branching in fronto-polar areas followed by episodic processing in superior frontal regions in GTS. Patients with GTS accomplish the integration of motor plans via qualitatively different neurophysiological processes.

A BS TRACT: Background: Motor symptoms in functional movement disorders (FMDs) are experienced as involuntary but share characteristics of voluntary action. Clinical and experimental evidence indicate alterations in monitoring, control, and subjective experience of selfperformed movements. Objective: The objective of this study was to test the prediction that FMDs are associated with a reduced ability to make accurate (metacognitive) judgments about self-performed movements. Methods: We compared 24 patients with FMD (including functional gait disturbance, functional tremor, and functional tics) with 24 age-and sex-matched healthy control subjects in a novel visuomotor-metacognitive paradigm. Participants performed target-directed movements on a graphics tablet with restricted visual feedback, decided which of two visually presented trajectories was closer to their preceding movement, and reported their confidence in the visuomotor decision. We quantified individual metacognitive performance as participants' ability to assign high confidence preferentially to correct visuomotor decisions.Results: Patients and control subjects showed comparable motor performance, response accuracy, and use of the confidence scale. However, visuomotor sensitivity in the trajectory judgment was reduced in patients with FMD compared with healthy control subjects. Moreover, metacognitive performance was impaired in patients, that is, their confidence ratings were less predictive of the correctness of visuomotor decisions. Exploratory subgroup analyses suggest metacognitive deficits to be most pronounced in patients with a functional gait disturbance or functional tremor. Conclusions: Patients with FMD exhibited deficits both when making visuomotor decisions about their own movements and in the metacognitive evaluation of these decisions. Reduced metacognitive insight into voluntary motor control may play a role in FMD pathophysiology and could lay the groundwork for new treatment strategies.

Number of references: 13 (> 12) Number of figures: 2 (<=2)

Definition und EpidemiologieBeim Gilles-de-la-Tourette-Syndrom (GTS) handelt es sich um eine komplexe neuropsychiatrische Spektrumstörung, die den Entwicklungsstörungen zugerechnet wird. Sie ist nach den ICD-10-Kriterien und DSM-V-Kriterien definiert durch das Vorkommen mehrerer motorischer Tics und mindestens eines vokalen Tics über einen Zeitraum von mindestens einem Jahr mit einem Beginn vor dem 18. Lebensjahr (▶ Tab. 1) [1-3]. Davon abzugrenzen sind eine chronische motorische Tic-Störung (Fehlen vokaler Tics), eine chronische vokale Tic-Störung (Fehlen motorischer Tics) sowie eine transiente Tic-Störung (Dauer der Tic-Störung weniger als 1 Jahr) [1, 3]. Vorübergehend auftretende Tics kommen bei vielen ansonsten gesunden Kindern vor; ihnen kommt per se dann kein Krankheitswert zu [4]. Bei der chronischen motorischen Tic-Störung sind die Tics sowie Häufigkeit und Schwere psychiatrischer Komorbiditäten meistens geringer ausgeprägt als beim Tourette-Syndrom [4].Mit einer Prävalenz, die je nach Literatur zwischen 0,3 und 1% angegeben wird, handelt es sich beim Tourette-Syndrom um eine der häufigsten neuropsychiatrischen Störungen. Jungen sind etwa 3-mal so häufig betroffen wie Mädchen; bei Erwachsenen ist das Geschlechterverhältnis ausgewogener [1,5,6]. MerkeDas Auftreten von Tics im Kindesalter ist häufig. Im Großteil der Fälle kommt diesen jedoch kein Krankheitswert zu. Klinik Motorische und vokale TicsAls Tics werden kurze, plötzlich auftretende, wiederholte Bewegungen oder Laute bezeichnet, die Bruchstücke von Bewegungen bzw. Äußerungen darstellen, im Kontext unpassend erscheinen und keinem besonderen Zweck dienen [1, 3]. Es werden nach ihrer Qualität vokale und motorische Tics sowie nach ihrer Komplexität einfache und komplexe Tics unterschieden [1]. Während einfache Tics kurze, umschriebene Bewegungen nur eines Körperteils darstellen, sind bei komplexen motorischen Tics verschiedene Muskelgruppen