Repetitive Finger Tapping Research Articles

Effect of concurrent action observation, peripheral nerve stimulation and motor imagery on dexterity in patients after stroke: a pilot study

Research to improve and expand treatment options for motor impairment after stroke remains an important issue in rehabilitation as the reduced ability to move affected limbs is still a limiting factor in the selection of training content for stroke patients. The combination of action observation and peripheral nerve stimulation is a promising method for inducing increased excitability and plasticity in the primary motor cortex of healthy subjects. In addition, as reported in the literature, the use of action observation and motor imagery in conjunction has an advantage over the use of one or the other alone in terms of the activation of motor-related brain regions. The aim of the pilot study was thus to combine these findings into a multimodal approach and to evaluate the potential impact of the concurrent application of the three methods on dexterity in stroke patients. The paradigm developed accordingly was tested with 10 subacute patients, in whom hand dexterity, thumb-index pinch force and thumb tapping speed were measured for a baseline assessment and directly before and after the single intervention. During the 10-min session, patients were instructed to watch a repetitive thumb-index finger tapping movement displayed on a monitor and to imagine the sensations that would arise from physically performing the same motion. They were also repeatedly electrically stimulated at the wrist on the motorically more affected body side and asked to place their hand behind the monitor for the duration of the session to support integration of the displayed hand into their own body schema. The data provide a first indication of a possible immediate effect of a single application of this procedure on the dexterity in patients after stroke.

The Role of Cerebellum and Basal Ganglia Functional Connectivity in Altered Voluntary Movement Execution in Essential Tremor

Substantial evidence highlights the role of the cerebellum in the pathophysiology of tremor in essential tremor (ET), although its potential involvement in altered movement execution in this condition remains unclear. This study aims to explore potential correlations between the cerebellum and basal ganglia functional connectivity and voluntary movement execution abnormalities in ET, objectively assessed with kinematic techniques. A total of 20 patients diagnosed with ET and 18 healthy subjects were enrolled in this study. Tremor and repetitive finger tapping were recorded using an optoelectronic kinematic system. All participants underwent comprehensive 3T-MRI examinations, including 3D-T1 and blood-oxygen-level dependent (BOLD) sequences during resting state. Morphometric analysis was conducted on the 3D-T1 images, while a seed-based analysis was performed to investigate the resting-state functional connectivity (rsFC) of dorsal and ventral portions of the dentate nucleus and the external and internal segments of the globus pallidus. Finally, potential correlations between rsFC alterations in patients and clinical as well as kinematic scores were assessed. Finger tapping movements were slower in ET than in healthy subjects. Compared to healthy subjects, patients with ET exhibited altered FC of both dentate and globus pallidus with cerebellar, basal ganglia, and cortical areas. Interestingly, both dentate and pallidal FC exhibited positive correlations with movement velocity in patients, differently from that we observed in healthy subjects, indicating the higher the FC, the faster the finger tapping. The findings of this study indicate the possible role of both cerebellum and basal ganglia in the pathophysiology of altered voluntary movement execution in patients with ET.

74 Timed Motor Performance in Children Medically Cleared for Return to Activities Post Mild Traumatic Brain Injury

Objective:Children who sustain a mild traumatic brain injury (mTBI) are at increased odds of additive injury and continue to show altered motor performance relative to never-injured peers after being medically cleared (MC) to return to normal activities. There is a critical need to determine when children can return to activities without risk of short and long-term adverse effects, with research showing high reinjury rates for 3-12 months after RTP. The Physical and Neurological Examination for Subtle Signs (PANESS) measures subtle signs of motor impairment during gait, balance, and timed motor functions. Recent literature has demonstrated that PANESS timed motor function can distinguish between children medically cleared post-mTBI compared to never-injured controls. The present study examined performance on timed motor tasks in youth medically cleared from mTBI following medical clearance and 3-months later, compared to never-injured peers.Participants and Methods:25 children (Mage=14.16, SD=2.46; Male=68%) were enrolled within 6 weeks of medical clearance from mTBI (Mdays post MC=33, SD=13.4, Range=2-59) along with 66 typically developing, never-injured controls (Mage=13.9, SD=2.22; Male=50%). Group differences were evaluated for the Timed Motor section of the PANESS at enrollment and at a 3-month follow-up (Mdays from enrollment to follow-up=95.90, SD=12.69, Range=62-129). This 3-month follow-up occurred on average 4 months after medical clearance (Mdays from MC to follow-up=130.08, SD=17.58, Range=92 - 164). The Timed Motor section includes Repetitive (foot tapping, hand patting, and finger tapping) and Sequential (heel-toe rocking, hand pronate/supinate, finger sequencing) raw time scores, measured in seconds. The Total Timed Motor Speed score is the combination of Repetitive and Sequential Movement and the side-to-side tongue item.Results:At 3-month follow-up, mTBI participants (M=67.55, SD=8.26, Range=53.66-83.88) performed worse than controls (M=63.09, SD=10.23, Range=39.86-100.51) on Total Timed Motor Speed, t(89)= 1.95, p<0.05), including when controlling for age and sex, F(1, 87)=4.67, p<0.05. At the same time point, mTBI participants (M=36.54, SD=5.47, Range=28.74-49.17) performed worse on Sequential Speed than controls (M=32.93, SD=6.1, Range=21.49-56.76), t(89)=2.59, p<0.01, including when controlling for age and sex, F(1, 87)=7.687, p<0.01). Although groups performed similarly on Sequential Speed at the initial time point, mTBI participants exhibited a trend of less improvement from initial to follow-up (MmTBI=-1.69, Mcontrol=-3.68, t(90)=1.445, p=0.076).Conclusions:Although groups did not significantly differ on Timed Motor Speed items at the initial time point, the mTBI group showed consistently lower scores than controls at both time points and less improvement over time. Results indicate that Total Timed Motor Speed, specifically Sequential Speed, may be a sensitive marker of persisting differences in high-level motor and cognitive learning/control in children who have been medically cleared after mTBI. More data are needed to evaluate these findings over a longer time period, and future studies should examine behavioral markers concurrently with physiologic brain recovery over time.

A pilot study for testing a low-cost 3D design with an inertial sensor for the quantitative assessment of finger tapping in patients with Parkinson's Disease.

Parkinson's disease (PD) is one of the most common neurodegenerative disorders worldwide. Current identification and monitoring of its motor symptoms depends on the clinical expertise. Repetitive finger tapping is one of the most common clinical maneuvers to assess for bradykinesia. Despite the increasing use of technology aids to quantitatively characterize the motor symptoms of PD, there is still a relative lack of clinical evidence to support their widespread use, particularly in low-resource settings. In this pilot study, we used a low-cost design prototype coupled with an inertial sensor is coupled to quantify the frequency of the finger tapping movements in four participants with PD. Repetitive finger tapping was performed using both hands before and after taking levodopa as part of their clinical treatment. The proposed 3D design allowed repetitive movements to be performed without issues. The maximum frequency of finger tapping was in the range of 0.1 to 4.3 Hz. Levodopa was associated with variable changes in the maximum frequency of finger tapping. This pilot study shows the feasibility for low-cost technology to quantitatively characterize repetitive movements in people living with PD.Clinical relevance- In this pilot study, a low-cost inertial sensor coupled to a design prototype was feasible to characterize the frequency of repetitive finger tapping movements in four participants with PD. This method could be used to quantitatively identify and monitor bradykinesia in people living with PD.

Negative Capacitance and Intrinsic Ferroelectric Behavior in α-MoO3 Culminating as a Robust Piezoelectric Energy Harvester

Driven by the notion that the spectrum of ferroelectric applications can be widened and the current subset of materials could be replaced with earth-abundant, lead-free materials, single-phase α-MoO3 (MO) with biaxial van der Waals gap was synthesized, revealing an orthorhombic Pmcn symmetry with a layered ABAB... sequence, with mirrored A and B layers. The force-driven dielectric constant of MO was found to be 12.5 at 0.5 N force level, which showed dielectric saturation behavior with increasing dynamic force. Ferroelectric studies revealed a maximum of 46% efficiency at 10 kV/cm external electric field, and piezoelectric modulus (d33) of 30 pC/N was obtained using the Berlincourt method. Negative capacitance (NC) effects were observed and attributed to the ferroelectric-induced emf and the inductive reactance, in accordance with Lenz’s law. Based on the confluence of the aforementioned features, a piezoelectric energy harvester (PEH) was fabricated, which reached a peak voltage of 4 V under repetitive finger tapping. The power density of the PEH under 100 MΩ resistive load was found to be 7.32 × 10–1 μW/cm2. This enshrines MO as a promising piezoelectric candidate with exotic properties that can be tailored to have multifaceted applications in the realm of sensing and energy harvesting to drive Internet-of-Things and Industry 4.0.

Dystonia as Presenting Feature of Compound Heterozygous PMPCA Gene Variants.

Video 1. This video shows the patient at 24 years. Dystonia is generalized, particularly severe at cranio-cervical level, but also involving the upper limbs. Speech is severely impaired. The clip shows involuntary orofacial movements, jaw-opening and tongue protrusion dystonia. At cervical level, there are abnormal postures and torsional movements relieved by a sensory trick (touching the chin with the left hand). Upper limb involvement is prevalent in the right arm with writer's cramp and evidence of mirror dystonia. Gait is broad-based with evident right foot dystonia accentuated by walking. Video 2. Video taken at home at age 29, three months after bilateral GPi implant. Dystonia has progressed. Facial grimaces are continuous, there is constantly flexed neck posture with head tilt to the right and rotational movements. Speech is not intelligible. Dystonic slowing is evident upon repetitive finger and foot tapping. There is bilateral dysmetria in the upper limbs. Sensory tricks (touching of eyelids) provides inconstant relief. The patient is unable to write. Diffuse muscle atrophy is evident, with normal strength. Deep tendon reflexes are brisk bilaterally. The patient is able to stand-up unassisted and uses a walker due to severe gait ataxia. Standing posture is characterized by severe neck and trunk flexion. Gait is wide-based with cock-walk appearance. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Short-term plasticity of the motor cortex compensates for bradykinesia in Parkinson’s disease

Patients with Parkinson's disease (PD) show impaired short-term potentiation (STP) mechanisms in the primary motor cortex (M1). However, the role played by this neurophysiological abnormality in bradykinesia pathophysiology is unknown. In this study, we used a multimodal neuromodulation approach to test whether defective STP contributes to bradykinesia. We evaluated STP by measuring motor-evoked potential facilitation during 5 Hz-repetitive transcranial magnetic stimulation (rTMS) and assessed repetitive finger tapping movements through kinematic techniques. Also, we used transcranial alternating current stimulation (tACS) to drive M1 oscillations and experimentally modulate bradykinesia. STP was assessed during tACS delivered at beta (β) and gamma (γ) frequency, and during sham-tACS. Data were compared to those recorded in a group of healthy subjects. In PD, we found that STP was impaired during sham- and γ-tACS, while it was restored during β-tACS. Importantly, the degree of STP impairment was associated with the severity of movement slowness and amplitude reduction. Moreover, β-tACS-related improvements in STP were linked to changes in movement slowness and intracortical GABA-A-ergic inhibition during stimulation, as assessed by short-interval intracortical inhibition (SICI). Patients with prominent STP amelioration had greater SICI reduction (cortical disinhibition) and less slowness worsening during β-tACS. Dopaminergic medications did not modify β-tACS effects. These data demonstrate that abnormal STP processes are involved in bradykinesia pathophysiology and return to normal levels when β oscillations increase. STP changes are likely mediated by modifications in GABA-A-ergic intracortical circuits and may represent a compensatory mechanism against β-induced bradykinesia in PD.

Quick computer aided differential diagnostics based on repetitive finger tapping in Parkinson’s disease and atypical parkinsonisms

BackgroundParkinson's disease (PD) is the second most common neurodegenerative disorder whose prevalence rises with age, yet clinical diagnosis is still a challenging task due to similar manifestations of other neurodegenerative movement disorders. In untreated patients or those with unclear responses to medication, correct percentages of early diagnoses go as low as 26%. Technology has been used in various forms to facilitate discerning between persons with PD and healthy individuals, but much less work has been dedicated to separating PD and atypical parkinsonisms. MethodsA wearable system was developed based on inertial sensors that capture the movements of fingers during repetitive finger tapping. A k-nearest-neighbor classifier was used on features extracted from gyroscope recordings for quick aid in differential diagnostics, discerning patients with PD, progressive supranuclear palsy (PSP), multiple system atrophy (MSA) and healthy controls (HC). ResultsThe overall classification accuracy achieved was 85.18% in the multiclass setup. MSA and HC groups were the easiest to discern (100%), while PSP was the most elusive diagnosis, as some patients were incorrectly assigned to MSA and HC groups. ConclusionsThe system shows potential for use as a tool for quick diagnostic aid, and in the era of big data, offers a means of standardization of data collection that could allow scientists to aggregate multi-center data for further research.

Gating at cortical level contributes to auditory-motor synchronization during repetitive finger tapping.

Sensory integration contributes to temporal coordination of the movement with external rhythms. How the information flowing of sensory inputs is regulated with increasing tapping rates and its function remains unknown. Here, somatosensory evoked potentials to ulnar nerve stimulation were recorded during auditory-cued repetitive right-index finger tapping at 0.5, 1, 2, 3, and 4Hz in 13 healthy subjects. We found that sensory inputs were suppressed at subcortical level (represented by P14) and primary somatosensory cortex (S1, represented by N20/P25) during repetitive tapping. This suppression was decreased in S1 but not in subcortical level during fast repetitive tapping (2, 3, and 4Hz) compared with slow repetitive tapping (0.5 and 1Hz). Furthermore, we assessed the ability to analyze temporal information in S1 by measuring the somatosensory temporal discrimination threshold (STDT). STDT increased during fast repetitive tapping compared with slow repetitive tapping, which was negatively correlated with the task performance of phase shift and positively correlated with the peak-to-peak amplitude (% of resting) in S1 but not in subcortical level. These novel findings indicate that the increased sensory input (lower sensory gating) in S1 may lead to greater temporal uncertainty for sensorimotor integration dereasing the performance of repetitive movement during increasing tapping rates.

Exploring the Role of Specialist Physiotherapy in Awake Craniotomy Surgery for the Neuro-Oncology Patient

Abstract AIMS To describe the methods used to assess and monitor motor function during awake craniotomy surgery for tumour resection. METHOD A service review was carried out over 10 months. Patients with highly motor eloquent lesions – invasion of primary motor cortex or fronto-parietal connections involved in motor cognition – were included. Clinical notes were reviewed and summarised using descriptive analysis. Dexterity and grip strength were measured using 9-hole peg test and handheld dynameter pre/intra and post-operatively. Patient occupation/interests were reported to guide bespoke assessments to trial intra-operatively. RESULTS From April 2021 to January 2022, 13 patients (mean age 39.7 years, 4 female:10 male, 9 low grade:5 high grade gliomas) were included. Mean score 9-hole peg test 22.2sec pre-operatively, 30.6sec post-operatively; handheld dynameter 26.7kg pre-operatively, 18.4kg post-operatively. At discharge 5 of 7 impaired patients demonstrated motor improvement. For motor coordination, motor tasks used frequently included repetitive finger tapping, open/closed hand. Bespoke tasks included texting/writing, playing instruments, and computer games. Movement was closely monitored and verbal feedback given to the neurosurgeons throughout. With video analysis movement comparisons were made. CONCLUSION The role of physiotherapy in awake surgery is evolving to provide movement analysis for complex motor tasks such as upper limb sequencing and dexterity. A combination of standard and bespoke assessments have been trialled and their feasibility within surgery tested. A post-operative deterioration of motor function (power and cognition) is expected after surgery for highly eloquent motor gliomas. However, intraoperative motor assessment for motor cognition allows function preservation and potentiates its recovery.

Cortical mechanisms of movement recovery after freezing in Parkinson's disease

Involuntary interruptions of upper limb movements, referred to as “upper limb freezing” (ULF) belong to the most disabling symptoms of Parkinson's disease (PD). Our study aimed to explore the cortical neuronal mechanisms underlying the reinstation of regular movement after a freezing episode and to control them by voluntary stops. We hypothesized that this movement recovery after a freeze would be accompanied by a decrease of beta power (13-30Hz) over the primary sensorimotor cortex (electrode “C3”). We recorded a 62-channel surface EEG in 14 PD patients during a repetitive finger tapping task. After performing time-frequency analysis of the EEG data we segmented it to i) regular finger taps, ii) ULF episodes, and iii) voluntary movement stops (VS). We analysed cortical activity during each movement modality and later focused on the last 500ms of ULF and VS and the first half of the following regular tap. At the beginning of regular finger taps we found decreased alpha power (6-12Hz) over C3 (P = 0.01). During ULF, there was no significant activity modulation in the alpha and beta frequency bands, whereas beta power increased over C3 during VS (P = 0.0038). When tapping was reinstated after a freeze, we found that 100ms before movement onset beta power decreased first present over C3, followed by fronto-central electrodes and then reaching the ipsilateral right fronto-temporal electrodes when reinstating regular tapping (P = 0.0256). Initiating movement after a VS showed a different pattern with a decrease of parieto-occipital beta activity 200ms prior to the first tap (P = 0.044). Our findings suggest that PD freezers make use of different cortical pathways when re-initiating movement after ULF or VS. This includes either fronto-central or parieto-occipital pathways. These findings may help to customize novel neuromodulation strategies to counteract freezing behaviour.

Free will strikes back: Steady-state movement-related cortical potentials are modulated by cognitive control

In psychology and neuroscience, opposition to free will has asserted that any degree of perceived self-control or choice is a mere epiphenomenon which provides no meaningful influence on action. The present research tested the validity of this conclusion by designing a paradigm in which the potential effect of self-monitoring on motor output could be investigated. Using a repetitive finger tapping task that evokes automatic patterns in participants tapping responses, we have obtained evidence that (1) participants may voluntarily reduce the predictability of their tapping patterns (2) by exercising cognitive control that (3) modulates response-locked steady-state movement-related potentials over primary and supplementary motor areas. These findings challenge the most radical accounts of the nonexistence of free will and instead provide support for a more balanced model of human behaviour in which cognitive control may constrain automatic response tendencies in response preparation and action execution.

Neurophysiological assessment of juvenile parkinsonism due to primary monoamine neurotransmitter disorders

No studies have investigated voluntary movement abnormalities and their neurophysiological correlates in patients with parkinsonism due to inherited primary monoamine neurotransmitter (NT) disorders. Nine NT disorders patients and 16 healthy controls (HCs) were enrolled. Objective measurements of repetitive finger tapping were obtained using a motion analysis system. Primary motor cortex (M1) excitability was assessed by recording the input/output (I/O) curve of motor-evoked potentials (MEP) and using a conditioning test paradigm for short-interval intracortical inhibition (SICI) assessment. M1 plasticity-like mechanisms were indexed according to MEPs amplitude changes after the paired associative stimulation protocol. Patient values were considered abnormal if they were greater or lower than two standard deviations from the average HCs value. Patients with aromatic amino acid decarboxylase, tyrosine hydroxylase, and 6-pyruvoyl-tetrahydropterin synthase defects showed markedly reduced velocity (5/5 patients), reduced movement amplitude, and irregular rhythm (4/5 patients). Conversely, only 1 out of 3 patients with autosomal-dominant GTPCH deficiency showed abnormal movement parameters. Interestingly, none of the patients had a progressive reduction in movement amplitude or velocity during the tapping sequence (no sequence effect). Reduced SICI was the most prominent neurophysiological abnormality in patients (5/9 patients). Finally, the I/O curve slope correlated with movement velocity and rhythm in patients. We provided an objective assessment of finger tapping abnormalities in monoamine NT disorders. We also demonstrated M1 excitability changes possibly related to alterations in motor execution. Our results may contribute to a better understanding of the pathophysiology of juvenile parkinsonism due to dopamine deficiency.

Slow Motion Analysis of Repetitive Tapping (SMART) Test: Measuring Bradykinesia in Recently Diagnosed Parkinson's Disease and Idiopathic Anosmia.

Bradykinesia is the defining motor feature of Parkinson's disease (PD). There are limitations to its assessment using standard clinical rating scales, especially in the early stages of PD when a floor effect may be observed. To develop a quantitative method to track repetitive tapping movements and to compare people in the early stages of PD, healthy controls, and individuals with idiopathic anosmia. This was a cross-sectional study of 99 participants (early-stage PD = 26, controls = 64, idiopathic anosmia = 9). For each participant, repetitive finger tapping was recorded over 20 seconds using a smartphone at 240 frames per second. From each video, amplitude between fingers, frequency (number of taps per second), and velocity (distance travelled per second) was extracted. Clinical assessment was based on the motor section of the MDS-UPDRS. People in the early stage of PD performed the task with slower velocity (p < 0.001) and with greater frequency slope than controls (p = 0.003). The combination of reduced velocity and greater frequency slope obtained the best accuracy to separate early-stage PD from controls based on metric thresholds alone (AUC = 0.88). Individuals with anosmia exhibited slower velocity (p = 0.001) and smaller amplitude (p < 0.001) compared with controls. We present a simple, proof-of-concept method to detect early motor dysfunction in PD. Mean tap velocity appeared to be the best parameter to differentiate patients with PD from controls. Patients with anosmia also showed detectable differences in motor performance compared with controls which may suggest that some were in the prodromal phase of PD.

Driving motor cortex oscillations modulates bradykinesia in Parkinson's disease.

In patients with Parkinson's disease, beta (β) and gamma (γ) oscillations are altered in the basal ganglia, and this abnormality contributes to the pathophysiology of bradykinesia. However, it is unclear whether β and γ rhythms at the primary motor cortex (M1) level influence bradykinesia. Transcranial alternating current stimulation (tACS) can modulate cortical rhythms by entraining endogenous oscillations. We tested whether β- and γ-tACS on M1 modulate bradykinesia in patients with Parkinson's disease by analysing the kinematic features of repetitive finger tapping, including movement amplitude, velocity and sequence effect, recorded during β-, γ- and sham tACS. We also verified whether possible tACS-induced bradykinesia changes depended on modifications in specific M1 circuits, as assessed by short-interval intracortical inhibition and short-latency afferent inhibition. Patients were studied OFF and ON dopaminergic therapy. Results were compared to those obtained in a group of healthy subjects. In patients, movement velocity significantly worsened during β-tACS and movement amplitude improved during γ-tACS, while the sequence effect did not change. In addition, short-latency afferent inhibition decreased (reduced inhibition) during β-tACS and short-interval intracortical inhibition decreased during both γ- and β-tACS in Parkinson's disease. The effects of tACS were comparable between OFF and ON sessions. In patients OFF therapy, the degree of short-interval intracortical inhibition modulation during β- and γ-tACS correlated with movement velocity and amplitude changes. Moreover, there was a positive correlation between the effect of γ-tACS on movement amplitude and motor symptoms severity. Our results show that cortical β and γ oscillations are relevant in the pathophysiology of bradykinesia in Parkinson's disease and that changes in inhibitory GABA-A-ergic interneuronal activity may reflect compensatory M1 mechanisms to counteract bradykinesia. In conclusion, abnormal oscillations at the M1 level of the basal ganglia-thalamo-cortical network play a relevant role in the pathophysiology of bradykinesia in Parkinson's disease.

Inhibitory Control of Adjacent Finger Movements while Performing a Modified Version of the Halstead Finger Tapping Test: Effects of Age, Education and Sex.

Selective motor inhibition is known to decline with age. The purpose of this study was to determine the frequency of failures at inhibitory control of adjacent finger movements while performing a repetitive finger tapping task in young, middle-aged and older adults. Potential education and sex effects were also evaluated. Kinematic recordings of adjacent finger movements were obtained on 107 healthy adults (ages 20-80) while they performed a modified version of the Halstead Finger Tapping Test (HTFF). Study participants were instructed to inhibit all finger movements while tapping with the index finger. Inability to inhibit adjacent finger movements while performing the task was infrequent in young adults (2.9% of individuals between 20 and 39 years of age) but increased with age (23.3% between the ages of 40 and 59; 31.0% between ages 60 and 80). Females and males did not differ in their inability to inhibit adjacent finger movements, but individuals with a college education showed a lower frequency of failure to inhibit adjacent finger movements (10.3%) compared to those with a high school education (28.6%). These findings were statistically significant only for the dominant hand. Selective motor inhibition failures are most common in the dominant hand and occur primarily in older healthy adults while performing the modified version of the HFTT. Monitoring selective motor inhibition failures may have diagnostic significance.

Is there evidence of bradykinesia in essential tremor?

Essential tremor (ET) is a movement disorder primarily characterized by upper limb postural and kinetic tremor. Although still under-investigated, bradykinesia may be part of the phenotypic spectrum of ET. The aim was to evaluate bradykinesia features in ET through clinical examination and kinematic analysis of repetitive finger movements. Data collected in ET patients were compared with those recorded in Parkinson's disease patients and healthy controls. Overall, 258 subjects participated in the study (90 ET patients, 84 Parkinson's disease patients and 84 healthy controls). Repetitive finger tapping was kinematically recorded using a motion analysis system. Movement velocity, amplitude and decrement (sequence effect) were measured. The three groups were first compared by one-way analysis of variance. A cluster analysis was also performed to better address the data variability observed in ET patients. Possible relationships between kinematic and clinical data were assessed in ET patients. Essential tremor patients were slower than healthy controls. Movement slowness in ET did not correlate with postural or kinetic tremor severity. It was also found that movement slowness in ET was not associated with a sequence effect, which instead is a common feature in Parkinson's disease. Cluster analysis showed that a proportion of ET patients may have movement abnormalities similar to those observed in Parkinson's disease. Movement slowness without sequence effect is a common feature in ET patients. The present findings are relevant when interpreted in the context of the new tremor classification system and in the development of a more accurate bradykinesia definition.

Bradykinesia in Alzheimer’s disease and its neurophysiological substrates

ObjectiveAlzheimer’s disease is primarily characterized by cognitive decline; recent studies, however, emphasize the occurrence of motor impairment in this condition. Here, we investigate whether motor impairment, objectively evaluated with kinematic techniques, correlates with neurophysiological measures of the primary motor cortex in Alzheimer’s disease. MethodsTwenty patients and 20 healthy subjects were enrolled. Repetitive finger tapping was assessed by means of a motion analysis system. Primary motor cortex excitability was assessed by recording the input/output curve of the motor-evoked potentials and using a conditioning-test paradigm for the assessment of short-interval intracortical inhibition and short-latency afferent inhibition. Plasticity-like mechanisms were indexed according to changes in motor-evoked potential amplitude induced by the intermittent theta-burst stimulation. ResultsPatients displayed slowness and altered rhythm during finger tapping. Movement slowness correlated with reduced short-latency afferent inhibition in patients, thus suggesting that degeneration of the cholinergic system may also be involved in motor impairment in Alzheimer’s disease. Moreover, altered movement rhythm in patients correlated with worse scores in the Frontal Assessment Battery. ConclusionThis study provides new information on the pathophysiology of altered voluntary movements in Alzheimer’s disease. SignificanceThe study results suggest that a cortical cholinergic deficit may underlie movement slowness in Alzheimer’s disease.

Effects of transcranial alternating current stimulation on repetitive finger movements in healthy humans

Transcranial Alternating Current Stimulation (tACS) is a non-invasive technique that can entrain brain oscillations. Few studies have investigated the effects of tACS on voluntary movements in healthy humans. We investigated whether tACS, delivered over M1 at beta and gamma frequencies, has any effect on repetitive finger tapping as assessed by means of kinematic analysis. Eighteen healthy subjects were enrolled. Objective measurements of repetitive finger tapping were obtained by using a motion analysis system. M1 excitability was assessed by single pulse TMS and measuring the amplitude of motor-evoked potentials. Movement kinematics and M1 excitability measures were collected during beta, gamma and sham tACS as well as off stimulation. Beta tACS led to an early amplitude decrement during repetitive finger tapping. Gamma tACS had the opposite effect. The progressive but short-lived modulatory effect of beta and gamma tACS on amplitude decrement was marked during the first movements of the motor sequence. No effect of tACS were found on other movement parameters neither on MEP amplitude. tACS modulates finger tapping in a frequency-dependent manner with no concurrent changes in corticospinal excitability. Thus, cortical beta and gamma oscillations are involved in the motor control of repetitive finger movements.

Effects of Transcranial Alternating Current Stimulation on Repetitive Finger Movements in Healthy Humans.

Transcranial alternating current stimulation (tACS) is a noninvasive neurophysiological technique that can entrain brain oscillations. Only few studies have investigated the effects of tACS on voluntary movements. We aimed to verify whether tACS, delivered over M1 at beta and gamma frequencies, has any effect on repetitive finger tapping as assessed by means of kinematic analysis. Eighteen healthy subjects were enrolled. Objective measurements of repetitive finger tapping were obtained by using a motion analysis system. M1 excitability was assessed by using single-pulse TMS and measuring the amplitude of motor-evoked potentials (MEPs). Movement kinematic measures and MEPs were collected during beta, gamma, and sham tACS and when the stimulation was off. Beta tACS led to an amplitude decrement (i.e., progressive reduction in amplitude) across the first ten movements of the motor sequence while gamma tACS had the opposite effect. The results did not reveal any significant effect of tACS on other movement parameters, nor any changes in MEPs. These findings demonstrate that tACS modulates finger tapping in a frequency-dependent manner with no concurrent changes in corticospinal excitability. The results suggest that cortical beta and gamma oscillations are involved in the motor control of repetitive finger movements.