Volitional action as perceptual detection: Predictors of conscious intention in adolescents with tic disorders

AbstractVoluntary actions are accompanied by a distinctive subjective experience, so that they feel quite different from physically similar involuntary movements. However, the nature and origin of this experience of volition remain unclear. Voluntary actions emerge during early childhood, in parallel with reduction of involuntary movements. However, the available markers of the experience of volition, notably Libet's mental chronometry of intention, cannot readily be used in young children. In Gilles de la Tourette syndrome (GTS), however, involuntary tic movements may coexist with voluntary control into adulthood. Therefore, adolescents with GTS could potentially confuse the two classes of movement. We have measured the temporal experience of voluntary action in a well-characterised group of adolescents with GTS, and age-matched controls. We replicated previous reports of a conscious intention occurring a few hundred milliseconds prior to voluntary keypress actions. Multiple regression across 25 patients' results showed that age and trait tic severity did not influence the experience of conscious intention. However, patients with stronger premonitory urges prior to tics showed significantly later conscious intentions, suggesting that the anticipatory experience of one's own volition involves a perceptual discrimination between potentially competing pre-movement signals. Patients who were more able to voluntarily suppress their tics showed significantly earlier conscious intention, suggesting that the perceptual discrimination between different action classes may also contribute to voluntary control of tics. We suggest that the brain learns voluntary control by perceptually discriminating a special class of internal ‘intentional’ signals, allowing them to emerge from motor noise

Learning volition: A longitudinal study of developing intentional awareness in Tourette syndrome

Tourette syndrome (TS) is characterized by the presence of involuntary movements (tics) which are, at least partly, generated within ‘voluntary’ motor pathways. Here we reassess 16 TS patients (age 19 ± 2.3 years) who participated in a mental chronometry study of volition 5.5 years previously (Ganos C et al. Cortex. 2015 Mar.; 64:47–54), and 16 age-matched controls. Participants estimated the time of their own voluntary movements (Libet's M judgement), or of conscious intention to make voluntary movements (Libet's W judgement), in separate blocks. We considered M judgement as a control condition. Therefore, the experience of an intention to move occurring prior to actual movement onset, as measured by the W-M gap, was taken as the cardinal feature of volition. Time estimates of the TS group did not differ significantly from controls, for either M or W judgement. Further, M and W time estimates in the TS group had not changed significantly between the two assessments. However, exploratory analyses revealed a strong relation between disease duration and the development of M- and W-judgements: the longer was the disease duration, the less was the developmental increase in the W-M gap (linear regression, p = .003). In conclusion, our results suggest compromised development of experience of volition in developing TS patients. The developmental difficulty in processing internal premotor signals for voluntary actions could reflect the chronic persistence of tics from adolescence to adulthood

ε-sarcoglycan myoclonus-dystonia—overview of neurophysiological, behavioral, and imaging characteristics

Myoclonus-Dystonia is a rare, neurological movement disorder, clinically characterized by myoclonic jerks and dystonic symptoms, such as cervical dystonia and writer’s cramp. Psychiatric symptoms, like anxiety, depression, and addiction, are frequently reported. Monogenic Myoclonus-Dystonia is mostly caused by pathogenic variants in the ε-sarcoglycan gene, which is among other regions highly expressed in the cerebellum. The current pharmacological treatment is not satisfactory. Neurophysiological and imaging studies in this patient population are scarce with partly heterogeneous results and sometimes important limitations. However, some studies point towards subcortical alterations, e.g., of the cerebellum and its connections. Further studies addressing previous limitations are important for a better understanding of the underlying pathology of Myoclonus-Dystonia and might build a bridge for the development of future treatment

Psychogenic paroxysmal movement disorders – Clinical features and diagnostic clues

AbstractBackgroundThe diagnosis of psychogenic paroxysmal movement disorders (PPMD) can be challenging, in particular their distinction from the primary paroxysmal dyskinesias (PxD) remains difficult.MethodsHere we present a large series of 26 PPMD cases, describe their characteristics, contrast them with primary PxD and focus on their distinguishing diagnostic features.ResultsMean age at onset was 38.6 years, i.e. much later than primary PxD. Women were predominantly affected (73%). Most subjects (88.4%) had long attacks, and unlike primary PxD there was a very high within-subject variability for attack phenomenology, duration and frequency. Dystonia was the most common single movement disorder presentation, but 69.2% of the patients had mixed or complex PxD. In 50% of PPMD cases attack triggers could be identified but these were unusual for primary PxD. 42.3% of patients employed unusual strategies to alleviate or stop the attacks. Response to typical medication used for primary PxD was poor. Precipitation of the disorder due to physical or emotional life events and stressors were documented in 57.6% and 65.3% of the cases respectively. Additional interictal psychogenic signs were documented in 34.6% and further medically unexplained somatic symptoms were present in 50% of the cases. 19.2% of patients had a comorbid organic movement disorder and 26.9% had pre-existing psychiatric comorbidities.ConclusionAlthough the phenotypic presentation of PPMD can be highly diverse, certain clinical characteristics help in distinguishing this condition from the primary forms of PxD. Recognition is important as multidisciplinary treatment approaches led to significant improvement in most cases

Right Temporoparietal Gray Matter Predicts Accuracy of Social Perception in the Autism Spectrum

Individuals with an autism spectrum disorder (ASD) show hallmark deficits in social perception. These difficulties might also reflect fundamental deficits in integrating visual signals. We contrasted predictions of a social perception and a spatial–temporal integration deficit account. Participants with ASD and matched controls performed two tasks: the first required spatiotemporal integration of global motion signals without social meaning, the second required processing of socially relevant local motion. The ASD group only showed differences to controls in social motion evaluation. In addition, gray matter volume in the temporal–parietal junction correlated positively with accuracy in social motion perception in the ASD group. Our findings suggest that social–perceptual difficulties in ASD cannot be reduced to deficits in spatial–temporal integration

Dollar Dominance, Euro Aspirations: Recipe for Discord?

After nearly a century of dominance of the international monetary system, has the US dollar finally met its match in the euro? When Europe’s Economic and Monetary Union (EMU) came into existence in 1999, many observers predicted that the euro would soon join America’s greenback at the peak of global finance. Achievements, however, have fallen short of aspirations. After an initial spurt of enthusiasm, international use of the euro now actually appears to be levelling off, even stalling, and so far seems confined largely to a limited range of market sectors and regions. The euro has successfully attained a place second only to the greenback, but it remains, and is likely to remain, a quite distant second without a determined effort by EMU authorities to promote their money’s global role. The temptation will surely be great. In practical terms, it is difficult to imagine that EMU authorities will refrain entirely from trying to promote a greater role for the euro. But that, in turn, could be a recipe for discord with the US, which has never made any secret of its commitment to preserving the greenback’s world-wide dominance. A struggle for monetary leadership could become a source of sustained tensions in US-European relations. Fortunately, however, there seems relatively little risk of a destabilising escalation into outright geopolitical conflict