The Click Test: A Novel Tool to Quantify the Age-Related Decline of Fast Motor Sequencing of the Thumb

International audienceAbstract : Background: The thumb plays a critical role for manual tasks during the activities of daily life and the incidence of neurological or musculoskeletal disorders affecting the voluntary movements of the thumb is high in the elderly. There is currently no tool to assess repetitive motor sequencing of the thumb during ageing.Objectives: To report a novel procedure (the Click Test) assessing the effects of ageing on fast motor sequencing of the thumb.Methods : Healthy subjects (n = 252; mean age +/- SD: 49.76 +/- 19.97 years; range: 19-89 years; F/M: 151/101) were asked to perform fast repeated flexion/extension movements of the thumb using a mechanical counter.Results: Motor performances (assessed by the number of clicks during 3 time periods: 15, 30 and 45 sec), significantly decreased as a function of age for both the dominant (age effect; p< 0.0001 for 15, 30 and 45 sec) and the non-dominant hand (p<0.0001 for 15, 30 and 45 sec). The number of clicks was significantly higher in males (gender effect; p<0.001) and was higher on the dominant side as compared to the non-dominant side (handedness effect: p<0.001). The Click Test is characterized by high repeatability (coefficients of variation from 3.20 to 4.47%), excellent intra-rater reliability (intra-class coefficients ICC ranging from 0.89 to 0.98), high inter-rater reproducibility (Pearson’s product correlation ranging from 0.85 to 0.96), high internal consistency (Cronbach alpha coefficient=0.95) and is highly correlated in terms of relative performances with the box and block test and the 9-hole peg test (positive linear correlation with the results of the box and block test: p<0.001 for 15, 30 and 45 sec for both the dominant and the non-dominant hand; negative linear correlation with the results of the 9-hole peg test: p<0.001 for 15, 30 and 45 sec for both the dominant and the non-dominant hand).Conclusion : The Click Test is an entirely novel and very low cost tool to reliably discriminate the ageing effects upon the performances during fast repetitive motor sequencing of the thumb. The potential clinical and research applications for motor functions are multiple, especially in acute and chronic neurological disorders affecting the thumb as well as in the field of rheumatology and orthopedics

Analysis of Speech and Language Impairments in Cerebellar Disorders

Cerebellar disorders can have various causes and their identification requires the expertise from a practitioner. Recently, a new technique based on speech performance measurement and classification has presented itself as a promising diagnostic tool. Recording speech is not trivial and some caution has to be taken regarding noise, recording equipment, data acquisition hardware, and software. The speech stimuli used in the recording are also important because they are not all suited for all use. They are divided into two main categories: speech and nonspeech stimuli. The same applies for the acoustic measures that can relate to the temporal or frequency domain. There have been studies that try to classify dysarthria based on speech acoustics. They show various accuracies based on disease severity and the acoustic measurement(s) used.SCOPUS: ch.binfo:eu-repo/semantics/publishe

A novel brain-computer interface (BCI) to assist upper limb pointing movements

Human to computer interaction only using thoughts is no longer a science fiction topic and recent progress made in this field are astounding. This work shows the creation of a novel upper limb pointing movement performance quantification platform (eCAM test) and its validation on a group of healthy subjects. After that, it shows that functional electrical stimulation (FES) enhances these upper limbs movements performance. Furthermore, this work shows that anodal transcranial direct current stimulation (atDCS) of the cerebellum impacts brain rhythms as well as postural tremor on a patient. Also, the MRI data gathered during this work will allow to better understand the underlying mechanisms of tDCS. Following that, it has been shown that the frequency and complexity of a tapping task increase the postural tremor of the contralateral limb. The same effect has been witnessed for neuromuscular fatigue. All these advances allowed us to place the foundations of a multimodal brain computer interface (BCI) based on sensors fusion. A development phase is now required to create this interface and test it on healthy and sick subjects.Communiquer avec un ordinateur par le biais de la pensée n'est plus un sujet de science-fiction et les progrès effectués dans le domaine sont ahurissants. Ce travail montre la création d'une nouvelle plateforme de mesure de la performance des mouvements de pointage verticaux (eCAM test) ainsi que sa validation sur une cohorte de sujets sains. Suite à cela, il montre que la stimulation électrique fonctionnelle (FES) améliore la performance de ces mouvements des membres supérieurs. En plus il démontre que la stimulation anodale trancranienne en courant continu (atDCS) du cervelet a un effet sur les rythmes des signaux cérébraux ainsi que sur le tremblement postural d'un patient. De plus des données IRM recueillies durant ce travail permettront de mieux cerner les mécanismes d'action de la stimulation tDCS. Suite à cela, il a été montré que la fréquence et la complexité d'une tâche de tapping augmentent le tremblement postural du membre controlatéral. Le même effet est constaté pour la fatigue musculaire. Toutes ces avancées installent les fondements à la création d'une interface cerveau-machine multimodale basée sur la fusion de senseurs. Une phase de développement est maintenant nécessaire pour établir cette interface et la tester sur des sujets sains et malades.Doctorat en Sciences biomédicales et pharmaceutiques (Médecine)info:eu-repo/semantics/nonPublishe

Enhancing transcranial direct current stimulation via motor imagery and kinesthetic illusion: Crossing internal and external tools

Background: Transcranial direct current stimulation is a safe technique which is now part of the therapeutic armamentarium for the neuromodulation of motor functions and cognitive operations. It is currently considered that tDCS is an intervention that might promote functional recovery after a lesion in the central nervous system, thus reducing long-term disability and associated socio-economic burden. Discussion: A recent study shows that kinesthetic illusion and motor imagery prolong the effects of tDCS on corticospinal excitability, overcoming one of the limitations of this intervention. Conclusion: Because changes in excitability anticipate changes in structural plasticity in the CNS, this interesting multi-modal approach might very soon find applications in neurorehabilitation.SCOPUS: re.jinfo:eu-repo/semantics/publishe

TDCS of the cerebellum: Where do we stand in 2016? Technical issues and critical review of the literature

Transcranial Direct Current Stimulation (tDCS) is an up-and-coming electrical neurostimulation technique increasingly used both in healthy subjects and in selected groups of patients. Due to the high density of neurons in the cerebellum, its peculiar anatomical organization with the cortex lying superficially below the skull and its diffuse connections with motor and associative areas of the cerebrum, the cerebellum is becoming a major target for neuromodulation of the cerebellocerebral networks. We discuss the recent studies based on cerebellar tDCS with a focus on the numerous technical and open issues which remain to be solved. Our current knowledge of the physiological impacts of tDCS on cerebellar circuitry is criticized. We provide a comparison with transcranial Alternating Current Stimulation (tACS), another promising transcranial electrical neurostimulation technique. Although both tDCS and tACS are becoming established techniques to modulate the cerebellocerebral networks, it is surprising that their impacts on cerebellar disorders remains unclear. A major reason is that the literature lacks large trials with a double-blind, sham-controlled, and cross-over experimental design in cerebellar patients.SCOPUS: re.jinfo:eu-repo/semantics/publishe

Targeting the Cerebellum by Noninvasive Neurostimulation: a Review

Transcranial magnetic and electric stimulation of the brain are novel and highly promising techniques currently employed in both research and clinical practice. Improving or rehabilitating brain functions by modulating excitability with these noninvasive tools is an exciting new area in neuroscience. Since the cerebellum is closely connected with the cerebral regions subserving motor, associative, and affective functions, the cerebello-thalamo-cortical pathways are an interesting target for these new techniques. Targeting the cerebellum represents a novel way to modulate the excitability of remote cortical regions and their functions. This review brings together the studies that have applied cerebellar stimulation, magnetic and electric, and presents an overview of the current knowledge and unsolved issues. Some recommendations for future research are implemented as well.SCOPUS: ar.jSCOPUS: re.jinfo:eu-repo/semantics/publishe

Marked reduction of cerebellar deficits in upper limbs following transcranial cerebello-cerebral DC stimulation: Tremor reduction and re-programming of the timing of antagonist commands

Cerebellar ataxias represent a very heterogeneous group of disabling disorders for which we lack effective symptomatic therapies in most cases. There is currently an intense interest in the use of non-invasive transcranial DC stimulation (tDCS) to modulate the activity of the cerebellum in ataxic disorders. We performed a detailed laboratory assessment of the effects of transcranial cerebello-cerebral DC stimulation (tCCDCS, including a sham procedure) on upper limb tremor and dysmetria in 2 patients presenting a dominant spinocerebellar ataxia (SCA) type 2, one of the most common SCAs encountered during practice. Both patients had a very similar triplet expansion size in the ATXN2 gene (respectively, 39 and 40 triplets). tCCDCS reduced both postural tremor and action tremor, as confirmed by spectral analysis. Quadratical PSD (power spectral density) of postural tremor dropped to 38.63 and 41.42% of baseline values in patient 1 and 2, respectively. The integral of the subband 4-20 Hz dropped to 46.9 and 62.3% of baseline values, respectively. Remarkably, tCCDCS canceled hypermetria and reduced dramatically the onset latency of the antagonist EMG activity associated with fast goal-directed movements toward 3 aimed targets (0.2, 0.3, and 0.4 rad). Following tCCDCS, the latency dropped from 108-98 to 63-57 ms in patient 1, and from 74-87 to 41-46 ms in patient 2 (mean control values ± SD: 36 ± 8 to 45 ± 11 ms), corresponding to a major drop of z scores for the 2 patients from 7.12 ± 0.69 to 1.28 ± 1.27 (sham procedure: 6.79 ± 0.71). This is the first demonstration that tCCDCS improves upper limb tremor and hypermetria in SCA type 2. In particular, this is the first report of a favorable effect on the onset latency of the antagonist EMG activity, a neurophysiological marker of the defect in programming of timing of motor commands. Our results indicate that tCCDCS should be considered in the symptomatic management of upper limb motor deficits in cerebellar ataxias. Future studies addressing a tDCS-based neuromodulation to improve motor control of upper limbs are required (a) in a large group of cerebellar disorders, and (b) in different subgroups of ataxic patients. The anatomical location of the cerebellum below the skull is particularly well suited for such studies. © 2014 Grimaldi, Oulad Ben Taib, Manto and Bodranghien.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

A Postural Tremor Highly Responsive to Transcranial Cerebello-Cerebral DCS in ARCA3

Background and objectives: Cerebellar ataxias are disabling disorders that impact the quality of life of patients. In many cases, an effective treatment is missing. Despite the increasing knowledge on the pathogenesis of cerebellar disorders including genetic aspects, there is currently a gap in the therapeutical management of cerebellar deficits. Cerebellar ataxia associated with ANO10 mutation (ARCA3) presents a disabling cerebellar syndrome. The aim of this study is to report a patient with a marked postural tremor responding to transcranial cerebello-cerebral direct current stimulation (tCCDCS). Methods: We applied tCCDCS using anodal stimulation over the cerebellum with a return electrode on the contralateral motor cortex. We performed a clinical rating, accelerometry studies, and recordings of voluntary movements at baseline, after sham, and after active tCCDCS. Results: A dramatic response of postural tremor was observed after tCCDCS, with a major drop of the power spectral density to 26.12% of basal values. Discussion: The postural tremor of cerebellar ataxia associated with ANO10 mutation was highly responsive to tCCDCS in our patient. This case illustrates that tCCDCS is a novel therapeutic option in the treatment of cerebellar deficits and might represent a promising tool to reduce tremor in ARCA3.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Cerebellar transcranial direct current stimulation reconfigurates static and dynamic functional connectivity of the resting-state networks

Background: Transcranial direct current stimulation (tDCS) of the cerebellum dynamically modulates cerebello-thalamo-cortical excitability in a polarity-specific manner during motor, visuo- motor and cognitive tasks. It remains to be established whether tDCS of the cerebellum impact also on resting-state intrinsically connected networks (ICNs). Such impact would open novel research and therapeutical doors for the neuromodulation of ICNs in human. Method: We combined tDCS applied over the right cerebellum and fMRI to investigate tDCS- induced resting-state intrinsic functional reconfiguration, using a randomized, sham-controlled design. fMRI data were recorded both before and after real anodal stimulation (2 mA, 20 min) or sham tDCS in 12 right-handed healthy volunteers. We resorted to a region-of-interest static correlational analysis and to a sliding window analysis to assess temporal variations in resting state FC between the cerebellar lobule VII and nodes of the main ICNs. Results: After real tDCS and compared with sham tDCS, functional changes were observed between the cerebellum and ICNs. Static FC showed enhanced or decreased correlation between cerebellum and brain areas belonging to visual, default-mode (DMN), sensorimotor and salience networks (SN) (p-corrected < 0.05). The temporal variability (TV) of BOLD signal was significantly modified after tDCS displaying in particular a lesser TV between the whole lobule VII and DMN and central executive network and a greater TV between crus 2 and SN. Static and dynamic FC was also modified between cerebellar lobuli. Conclusion: These results demonstrate short- and long-range static and majorly dynamic effects of tDCS stimulation of the cerebellum affecting distinct resting-state ICNs, as well as intracerebellar functional connectivity, so that tDCS of the cerebellum appears as a non-invasive tool reconfigurating the dynamics of ICNs.SCOPUS: ar.jinfo:eu-repo/semantics/publishe