Repetitive Finger Research Articles

Attribution of sensory prediction error to perception of muscle fatigue

Sensory prediction-error is vital to discriminating whether sensory inputs are caused externally or are the consequence of self-action, thereby contributing to a stable perception of the external world and building sense of agency. However, it remains unexplored whether prediction error of self-action is also used to estimate the internal body condition. To address this point, we examined whether prediction error affects the perceived intensity of muscle fatigue. Participants evaluated fatigue while maintaining repetitive finger movements. To provide prediction error, we inserted a temporal delay into online visual feedback of self-movements. The results show that the subjective rating of muscle fatigue significantly increased under the delayed visual feedback, suggesting that prediction error enhances the perception of muscle fatigue. Furthermore, we introduced visual feedback that preceded actual finger movements to test whether the temporal direction of the mismatch is crucial in estimating muscle fatigue. We found that perceived fatigue was significantly weaker with preceding visual feedback compared to normal feedback, showing that the perception of muscle fatigue is affected by the signed prediction-error. Our findings support the idea that the brain flexibly attributes prediction errors to a self-origin with keeping sense of agency, or external origin by considering contexts and error characteristics.

S3663 Refractory Hypoglycemia Induced by a Gastrointestinal Stromal Tumor Secreting Insulin-Like Growth Factor-2

Introduction: Non-islet cell tumor hypoglycemia (NICTH) is a rare paraneoplastic syndrome that leads to the release of insulin-like growth factor-2 (IGF-2). It is commonly associated with tumors of mesenchymal origin like gastrointestinal stromal tumors (GIST). Case Description/Methods: A 62-year-old male, with a past medical history of recently diagnosed GIST was started on imatinib but stopped taking it one month ago pending surgical evaluation, presents with altered mental status due to severe hypoglycemia. The patient had no prior history of diabetes or adrenal insufficiency. The patient's repetitive finger sticks glucose remained persistently low even after good oral intake and two D50 pushes. Urine toxicology and drug screen for sulfonylureas were negative. Laboratory investigations showed reduced levels of insulin, C-peptide, and insulin-like growth factor-1 (IGF-1), but his IGF-2 was increased. Endocrinology was consulted for refractory hypoglycemia; recommended to start D10 fluids in the setting of resistant low blood glucose and start octreotide and steroids. Insulinoma was unlikely as insulin and C-peptides were low. CT chest/abdomen/pelvis shows grossly unchanged gastric GIST, measuring 25 × 19.6 × 11.4 cm with no evidence of metastatic disease in the abdomen or pelvis (Figure 1A). Esophagogastroduodenoscopy (EGD) demonstrated large, bilobed subepithelial mass measuring 10-15 cm with an area of ulceration within the mass (Figure 1B) followed up with Endoscopic ultrasound (EUS) demonstrating subepithelial lesion was found likely arising from the fundus, lesser curve and body of the stomach, layer of origin could not be determined on due to the large size of the mass (Figure 1C). Oncology was consulted for further management of malignancy; imatinib was resumed and referred for surgical evaluation for tumor removal. Discussion: IGF-II acts as an autocrine growth factor in tumor cells therefore, it is highly likely that IGF-II will be high in case of high tumor bulk and making them at high risk of developing NICTH. In patients diagnosed with GIST with hypoglycemic symptoms, we should consider IGF-II secreting GIST in addition to insulinoma especially in bulky tumors.Figure 1.: A: CT scan abdomen/pelvis with contrast showing large soft tissue density mass inseparable from the lesser curvature of the stomach marked with asterisk. B: EGD findings consistent with a large, bilobed subepithelial mass measuring 10-15 cm with an area of ulceration within the mass (seen best on retroflexion) was found on the lesser curvature of the stomach along the anterior wall of the stomach. C: Endoscopic US findings showed A 43.0 mm × 77.8 mm subepithelial lesion was found likely arising from the fundus, lesser curve and body of the stomach s/p FNB × 4. The lesion was hypoechoic and had some cystic spaces within it in some areas. Sonographically, the lesion appeared to originate from the stomach, but the wall layers could not be determined due to the large size of the mass.

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.

Operation Stability Analysis of Basic Acupuncture Manipulation Based on Three-Dimensional Motion Tracking Data

Objective. To analyse the operational stability of basic acupuncture manipulation (AM) based on three-dimensional (3D) motion tracking. Method. Two quantitative indicators (spatial and temporal dispersions) and corresponding algorithms of operation stability were established based on the coordinate-time data derived from 3D motion tracking of basic AM. The differences in stability were compared between 20 acupuncture teachers and 20 acupuncture students. Results. The teachers and students had similar temporal stability, but the teachers were more stable in their spatial control, perhaps because of the teachers’ better fingertip force and more practice with feedback. Conclusion. The spatial and temporal dispersions can be used to evaluate operational stability in basic AM. Repetitive training and finger force enhancement with more accurate feedback and rhythmic auditory stimulation are recommended for improving operation stability in basic AM.

Musical training improves fine motor function in adolescents

Background: Adolescence is a sensitive period in motor development but little is known about how long-term learning dependent processes shape hand function in tasks of different complexity.Procedure: We mapped two fundamental aspects of hand function: simple repetitive and complex sequential finger movements, as a function of the length of musical instrumental training. We controlled maturational factors such as chronological and biological age of adolescent female participants (11 to 15 years of age, n = 114).Results: We demonstrated that experience improves performance as a function of task complexity, the more complex task being more susceptible for experience driven performance changes.Conclusion: Overall, these results suggest that fine motor skills involving cognitive control and relying on long-range functional brain networks are substantially shaped by experience. On the other hand, performance in a simple repetitive task that explains fine motor speed is primarily determined by white matter development driven by maturational factors.

Combining inertial sensors and optical flow to assess finger movements: Pilot study for telehealth applications.

Parkinson's disease is the fastest growing neurological disorder worldwide. Traditionally, diagnosis and monitoring of its motor manifestations depend on examination of the speed, amplitude, and frequency of movement by trained providers. Despite the use of validated scales, clinical examination of movement is semi-quantitative, relatively subjective and it has become a major challenge during the ongoing pandemic. Using digital and technology-based tools during synchronous telehealth can overcome these barriers but it requires access to powerful computers and high-speed internet. In resource-limited settings without consistent access to trained providers, computers and internet, there is a need to develop accessible tools for telehealth application. We simulated a controlled asynchronous telehealth environment to develop and pre-test optical flow and inertial sensors (accelerometer and gyroscope) to assess sequences of 10 repetitive finger-tapping movements performed at a cued frequency of 1 Hz. In 42 sequences obtained from 7 healthy volunteers, we found positive correlations between the frequencies estimated by all modalities (ρ=0.63-0.93, P<0.01). Test-retest experiments showed median coefficients of variation of 7.04% for optical flow, 7.78% for accelerometer and 11.79% for gyroscope measures. This pilot study shows that combining optical flow and inertial sensors is a potential telehealth approach to accurately measure the frequency of repetitive finger movements.Clinical relevance- This pilot study presents a comparative analysis between inertial sensors and optical flow to characterize repetitive finger-tapping movements in healthy volunteers. These methods are feasible for the objective evaluation of bradykinesia as part of telehealth applications.

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.

Bradykinesia in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is primarily characterized by the degeneration of motor neurons, leading to muscle weakness and motor impairment. There are some clinical reports of bradykinesia in this condition, but no studies have objectively assessed voluntary movements in these patients. The relationship between motor neurons involvement and movement abnormalities is also unknown. We here kinematically assessed repetitive finger movements in patients with amyotrophic lateral sclerosis as compared to healthy controls. We investigated possible relationships between altered movement kinematics and neurophysiological measures of motor neurons involvement in patients.

A comparative study using electromyography to assess hand exercises for rehabilitation after ulnar nerve decompression

Ulnar nerve (UN) entrapment is a common peripheral neuropathy and can lead to dysfunction of both sensory and motor function of the hand. Surgical release is the mainstay of treatment, but post-operative rehabilitation of UN innervated intrinsic muscles is lacking evidence. This cohort study utilized surface electromyography (EMG) and assessed the activation of UN innervated intrinsic and extrinsic hand muscles during four exercises in healthy participants. Exercises included rotating baoding balls, squeezing a stress ball or grip device every second, and repetitive finger abduction against a rubber band. Normalized percent activation of each muscle was calculated for each exercise. It was demonstrated that rubber band resistance (RBR) finger abduction showed significantly increased activation in both intrinsic muscles tested, while minimizing activation of the one tested UN innervated extrinsic muscle. Thus, to best target the intrinsic hand muscles without fatiguing extrinsic muscles, the inexpensive and practical RBR exercise is beneficial in post-UN release rehabilitation.

P 40. β-γ phase-amplitude coupling during movements in Parkinson's disease

Question. Enhanced phase amplitude coupling (PAC) between β (13–30 Hz) and broadband γ (50–150 Hz) activities has been found in surface EEG recordings from Parkinson patients at rest [1]. However, the dynamics of PAC during voluntary movement and its relationship with motor impairment of Parkinson“s disease (PD) remain unclear. Methods. Experimental design : We recorded 64-channel EEG signals from 19 PD patients and 20 sex- and age-matched healthy controls at rest, during a repetitive pressing task and during repetitive index finger tapping performed at the patients“ own pace and at their fastest pace. Source analysis : We obtained source signals by projecting EEG sensor signals to the individual cortical surfaces. Independent component analysis (ICA) was applied for separating temporally independent subnetworks of each task in each of the 4 brain regions: premotor cortex, primary motor cortex, primary somatosensory cortex and primary somatosensory complex. PAC analysis: Pairwise transient PAC values were calculated among ICA components of each region by zscore-normalized mean vector length [2] in 300ms windows shifted with 50ms time steps in 3s epochs which included an interval of 1s before, and 2s after the onset of the movement. Statistics : We applied a non-parametric three-way ANOVA [3] to test the effects of the disease state, tasks and different brain regions on PAC. For post-hoc testing, a two tailed Wilcoxon ranksum test was used between groups and Wilcoxon signrank test within groups. Results. As expected, maximum tapping rate was lower, and fastest movements were executed more irregularly in patients compared to controls. ANOVA performed on the β-γ PAC values averaged over the entire 3s-epoch revealed an interaction of disease state and tasks ( p < 0.001). Post-hoc testing showed enhanced PAC in patients compared with controls in the resting state ( p = 0.018), in agreement with previous findings, but not in any of the tapping tasks. However, PAC during the pressing task remained elevated in the patients compared to controls ( p = 0.020). Analysis of the temporal dynamics revealed reduction of PAC after the onset of the movement (0–0.25 s) compared with that of the pre-onset period (−0.5 to −0.25 s). The reduction of PAC relative to pre-onset period correlated with the desynchronization in the β power. However, the PAC reduction relative to the resting state was not correlated with the β power reduction. Discussion. Persistence of PAC differences during the pressing task on one hand, and disappearance of PAC differences during the tapping tasks on the other hand, suggest that exaggerated β-broadband γ PAC, as detected in the resting EEG, is not necessarily directly related to impaired motor behavior in PD patients. As our previous findings [1] have shown that abnormal PAC at rest is unrelated to the β band power, partial renormalization of PAC by movement-related β band desynchronization may suggest that mechanisms modulating β activity during movement may selectively affect β activity involved in abnormal coupling.

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.

Electromyography-controlled gamified exercise system for the distal upper extremity: a usability assessment in subacute post-stroke patients

Purpose Movement repetition is known to play a key role in promoting functional improvements or maintaining functional levels in post-stroke hemiparetic patients. However, repetitive movements tend to be monotonous, making it challenging for patients to continue. Here, we developed a new gamified system to allow patients perform repetitive movements with enjoyment. The present study aimed to examine the usability of the system in subacute stroke patients. Method The exercise system comprised an electromyography-controlled operating system that enabled users to play a virtual game by repetitive finger and wrist movements on the affected side. A total of 13 patients with upper-limb hemiparesis underwent a single bout of exercise using the system and assessed its usability, satisfactoriness, enjoyability, etc. using the System Usability Scale (SUS), Quebec User Evaluation of Satisfaction with assistive Technology (QUEST)-like questionnaire, and numerical rating scale (NRS). Results All the participants, who had a wide range of paretic levels, were able to perform the exercise using the system. Participants scored the system a median of 85.0 for SUS and 4.2 for the QUEST-like questionnaire, with an “excellent” in usability and “satisfied” in user satisfaction with the system. The median NRS scores for enjoyability, potential for continuous use, and effectiveness were 8.0, 9.0, and 9.0, respectively, which were greater than the scores for usual rehabilitation training for the upper extremity. Conclusions The novel electromyography-controlled gamified exercise system may have sufficient usability and enjoyability to motivate patients with a wide range of paretic levels to perform repetitive finger and wrist movements. IMPLICATIONS FOR REHABILITATION The electromyography-controlled gamified exercise system had overall positive perspectives on the usability of the system. This exercise system could help motivate patients with a wide range of paretic levels to perform repetitive finger and wrist movements.

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.

Ultrasound examination predicts 6-month progression in carpal tunnel syndrome patients.

Carpal tunnel syndrome (CTS) is a peripheral neuropathy resulting from chronic median nerve compression. Chronic compression leads to neurological changes that are quantified through nerve conduction studies (NCS). Although NCS represents the gold standard in CTS assessment, they provide limited prognostic value. Several studies have identified ultrasound as a tool in diagnosing and potentially predicting the progression of CTS in patients. The purpose of this study was to evaluate the predictive value of ultrasound examination in CTS patients. Twenty patients recruited at their first visit with the neurologist completed two NCS and ultrasound examinations approximately 6 months apart. Ultrasound examination consisted of B-mode, pulse-wave Doppler and colour Doppler ultrasound videos and images to quantify median nerve cross-sectional area, intraneural blood flow velocity in three wrist postures (15° flexion, neutral, and 30° extension), and displacement of the flexor digitorum superficialis (FDS) tendon and the adjacent subsynovial connective tissue (SSCT) of the middle finger during repetitive finger flexion-extension cycles. A questionnaire was administered to assess the work-relatedness of CTS. Linear regression analyses revealed that intraneural blood flow velocity (R2 = 0.36, p = .03), assessed in wrist flexion, and relative FDS-SSCT displacement (R2 = 0.27, p = .04) and shear strain index (R2 = 0.28, p = .04) were significant predictors of nerve sensory and motor changes at 6 months. Results suggest the possibility of using a battery of ultrasound measures as viable markers to predict median nerve functional changes within 6 months.

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.

ECoG Beta Suppression and Modulation During Finger Extension and Flexion

Neural oscillations originate predominantly from interacting cortical neurons and consequently reflect aspects of cortical information processing. However, their functional role is not yet fully understood and their interpretation is debatable. Amplitude modulations (AMs) in alpha (8–12 Hz), beta (13–30 Hz), and high gamma (70–150 Hz) band in invasive electrocorticogram (ECoG) and non-invasive electroencephalogram (EEG) signals change with behavior. Alpha and beta band AMs are typically suppressed (desynchronized) during motor behavior, while high gamma AMs highly correlate with the behavior. These two phenomena are successfully used for functional brain mapping and brain-computer interface (BCI) applications. Recent research found movement-phase related AMs (MPA) also in high beta/low gamma (24–40 Hz) EEG rhythms. These MPAs were found by separating the suppressed AMs into sustained and dynamic components. Sustained AM components are those with frequencies that are lower than the motor behavior. Dynamic components those with frequencies higher than the behavior. In this paper, we study ECoG beta/low gamma band (12–30 Hz/30–42 Hz) AM during repetitive finger movements addressing the question whether or not MPAs can be found in ECoG beta band. Indeed, MPA in the 12–18 Hz and 18–24 Hz band were found. This additional information may lead to further improvements in ECoG-based prediction and reconstruction of motor behavior by combining high gamma AM and beta band MPA.

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.