Assessment of fine motor control in individuals with Parkinson's disease using force tracking with a secondary cognitive task

Inter-Digit Low Level Force Coordination in a Complex Isometric Pinch Tracking Task

This study examined whether target pursuit tracking by a performer-controlled computer cursor around a square diamond-shaped circuit, using isometric pinch grip force production, would show a significant difference in performance metrics dependent on the clockwise sense of the target movement along the trajectory path. The target template incorporated path segments requiring all four possible combinations of directional force modulation patterns (increasing and decreasing isometric pinch forces of the thumb and index finger). Overall, it was found that cursor positional accuracy was greater during counterclockwise pursuit, that steadiness was greater during clockwise pursuit, and that the cursor bearing angle with respect to target movement was biased toward cursor positioning being within the interior of the trajectory circuit regardless of clockwise sense.

Upper limb intention tremor assessment: opportunities and challenges in wearable technology

BACKGROUND

Tremors are involuntary rhythmic movements commonly present in neurological diseases such as Parkinson's disease, essential tremor, and multiple sclerosis. Intention tremor is a subtype associated with lesions in the cerebellum and its connected pathways, and it is a common symptom in diseases associated with cerebellar pathology. While clinicians traditionally use tests to identify tremor type and severity, recent advancements in wearable technology have provided quantifiable ways to measure movement and tremor using motion capture systems, app-based tasks and tools, and physiology-based measurements. However, quantifying intention tremor remains challenging due to its changing nature.

METHODOLOGY & RESULTS

This review examines the current state of upper limb tremor assessment technology and discusses potential directions to further develop new and existing algorithms and sensors to better quantify tremor, specifically intention tremor. A comprehensive search using PubMed and Scopus was performed using keywords related to technologies for tremor assessment. Afterward, screened results were filtered for relevance and eligibility and further classified into technology type. A total of 243 publications were selected for this review and classified according to their type: body function level: movement-based, activity level: task and tool-based, and physiology-based. Furthermore, each publication's methods, purpose, and technology are summarized in the appendix table.

CONCLUSIONS

Our survey suggests a need for more targeted tasks to evaluate intention tremors, including digitized tasks related to intentional movements, neurological and physiological measurements targeting the cerebellum and its pathways, and signal processing techniques that differentiate voluntary from involuntary movement in motion capture systems.

Neuromuscular assessment of force development, postural, and gait performance under cognitive-motor dual-tasking in healthy older adults and people with early Parkinson's disease: Study protocol for a cross-sectional Mobile Brain/Body Imaging (MoBI) study

Background

Neuromuscular dysfunction is common in older adults and more pronounced in neurodegenerative diseases. In Parkinson's disease (PD), a complex set of factors often prevents the effective performance of activities of daily living that require intact and simultaneous performance of the motor and cognitive tasks.

Methods

The cross-sectional study includes a multifactorial mixed-measure design. Between-subject factor grouping the sample will be Parkinson's Disease (early PD vs. healthy). The within-subject factors will be the task complexity (single- vs. dual-task) in each motor activity, i.e., overground walking, semi-tandem stance, and isometric knee extension, and a walking condition (wide vs. narrow lane) will be implemented for the overground walking activity only. To study dual-task (DT) effects, in each motor activity participants will be given a secondary cognitive task, i.e., a visual discrimination task for the overground walking, an attention task for the semi-tandem, and mental arithmetic for the isometric extension. Analyses of DT effects and underlying neuronal correlates will focus on both gait and cognitive performance where applicable. Based on an a priori sample size calculation, a total N = 42 older adults (55-75 years) will be recruited. Disease-specific changes such as laterality in motor unit behavior and cortical control of movement will be studied with high-density surface electromyography and electroencephalography during static and dynamic motor activities, together with whole-body kinematics.

Discussion

This study will be one of the first to holistically address early PD neurophysiological and neuromuscular patterns in an ecologically valid environment under cognitive-motor DT conditions of different complexities. The outcomes of the study aim to identify the biomarker for early PD either at the electrophysiological, muscular or kinematic level or in the communication between these systems.

Clinical Trial Registration

ClinicalTrials.Gov, NCT05477654. This study was approved by the Medical Ethical Committee (106/2021).

Circuits and Biomarkers of the Central Nervous System Relating to Astronaut Performance: Summary Report for a NASA-Sponsored Technical Interchange Meeting

Biomarkers, ranging from molecules to behavior, can be used to identify thresholds beyond which performance of mission tasks may be compromised and could potentially trigger the activation of countermeasures. Identification of homologous brain regions and/or neural circuits related to operational performance may allow for translational studies between species. Three discussion groups were directed to use operationally relevant performance tasks as a driver when identifying biomarkers and brain regions or circuits for selected constructs. Here we summarize small-group discussions in tables of circuits and biomarkers categorized by (a) sensorimotor, (b) behavioral medicine and (c) integrated approaches (e.g., physiological responses). In total, hundreds of biomarkers have been identified and are summarized herein by the respective group leads. We hope the meeting proceedings become a rich resource for NASA's Human Research Program (HRP) and the community of researchers.

Which motor-cognitive abilities underlie the digital Trail-Making Test? Decomposing various test scores to detect cognitive impairment in Parkinson's disease-Pilot study

Since Parkinson's disease (PD) is a heterogeneous disorder with symptoms, such as tremors, gait and speech disturbances, or memory loss, individualized diagnostics are needed to optimize treatment. In their current form, the typical paper-pencil methods traditionally used to track disease progression are too coarse to capture the subtleties of clinical phenomena. For this reason, digital biomarkers that capture, for example, motor function, cognition, and behavior using apps, wearables, and tracking systems are becoming increasingly established. However, given the high prevalence of cognitive impairment in PD, digital cognitive biomarkers to predict mental progression are important in clinical practice. This pilot study aimed to identify those components of our digital version of the TMT (dTMT) that allow discrimination between PD patients with and without cognitive deficits. A total of 30 healthy control (age 66.3 ± 8.61) and 30 participants with PD (age 68.3 ± 9.66) performed the dTMT using a touch-sensitive tablet to capture enhanced performance metrics, such as the speed between and inside circles. The decomposition of cognitive abilities based on integrating additional variables in the dTMT revealed that the Parkinson's disease group was significantly more sensitive to parameters of inhibitory control. In contrast, the mild cognitive impairment group was sensitive to parameters of cognitive flexibility and working memory. The dTMT allows objective, ecologically valid, and long-term cognitive and fine-motor performance tracking, suggesting its potential as a digital biomarker in neurodegenerative disorders.

Decrease in force control among older adults under unpredictable conditions

OBJECTIVES

Falls in older adults generally occur during unpredictable situations. Controlling posture through fine-tuned muscle force before and after falls is necessary to avoid serious injuries. However, details regarding force control among older adults during unpredictable situations are unclear. This study determined the features of force control in a random force-tracking task among older adults.

METHODS

Ten healthy older adults (67-76 years) and eight healthy young adults (20-23 years) participated in three force-tracking tasks with ankle plantar flexion: low-range (LR), high-range (HR), and pseudo-random (PR) force tasks. Force control ability was assessed using the root mean square error (RMSE) between the target and muscle forces produced by the participants. Muscle activities from the lateral head of the gastrocnemius and the tibialis anterior during each task were measured using surface electromyography to calculate the co-contraction index (CCI).

RESULTS

In all tasks, older adults (RMSEs: 1.09-3.70, CCIs: 29.4-56.4) had a significantly greater RMSEs and CCIs than young adults (RMSEs: 0.49-1.83, CCIs: 11.7-20.6; all, p < 0.05). The RMSEs during force generation were significantly greater than those during force release (LR: p < 0.01, HR: p < 0.05), except for the random force-tracking task in older adults. CCIs during the force release phase in both groups (older adults: 27.8-56.4, young adults: 15.0-20.6) were consistently greater than those during force generation (older adults: 24.5-50.4, young adults: 11.7-17.2). CCIs in force-tracing tasks differed in older adults, whereas those in the random force-tracing task increased. RMSEs and CCIs in the random and LR force-tracing tasks were significantly negatively correlated with the functional reach test (all: r > 0.5, p < 0.05).

CONCLUSION

Force control in older adults declines in low-band and random muscle force output. Moreover, increased CCIs in older adults are particularly pronounced during unpredictable situations.

Long-Term Application of Cerebellar Transcranial Direct Current Stimulation Does Not Improve Motor Learning in Parkinson's Disease

Cerebellar transcranial direct current stimulation (c-tDCS) enhances motor skill acquisition and motor learning in young and old adults. Since the cerebellum is involved in the pathophysiology of Parkinson’s disease (PD), c-tDCS may represent an intervention with potential to improve motor learning in PD. The primary purpose was to determine the influence of long-term application of c-tDCS on motor learning in PD. The secondary purpose was to examine the influence of long-term application of c-tDCS on transfer of motor learning in PD. The study was a randomized, double-blind, SHAM-controlled, between-subjects design. Twenty-one participants with PD were allocated to either a tDCS group or a SHAM stimulation group. Participants completed 9 practice sessions over a 2-week period that involved extensive practice of an isometric pinch grip task (PGT) and a rapid arm movement task (AMT). These practice tasks were performed over a 25-min period concurrent with either anodal c-tDCS or SHAM stimulation. A set of transfer tasks that included clinical rating scales, manual dexterity tests, and lower extremity assessments were quantified in Test sessions at Baseline, 1, 14, and 28 days after the end of practice (EOP). There were no significant differences between the c-tDCS and SHAM groups as indicated by performance changes in the practice and transfer tasks from Baseline to the 3 EOP Tests. The findings indicate that long-term application of c-tDCS does not improve motor learning or transfer of motor learning to a greater extent than practice alone in PD.

A new visual feedback-based system for the assessment of pinch force, endurance, accuracy and precision. A test-retest reliability study

Introduction

Given that pinch is a precision grip involved in sustained submaximal activities, a Sustained Contraction (SC) task could be associated to Maximal Voluntary Contraction (MVC). To better evaluate the thumb-index system, the test-retest reliability of pinch MVC and SC, measured by a visual feedback-based pinch gauge was assessed.

Methods

26 healthy participants performed MVC and SC in two separate sessions. SC required to maintain 40%MVC as long as possible and it was evaluated in terms of time, accuracy (Mean Distance between force trace and target force, MD), precision (Coefficient of Variability of force trace, CV). MD and CV analyses were conducted dividing the SC task into three equivalent time stages (beginning, middle, exhaustion). Relative Reliability (RR) was measured by Intraclass Correlation Coefficient, and Absolute Reliability (AR) was measured by Standard Error of Measurement and by Bland-Altman plot.

Results

MVC and Time showed high RR and AR in both hands. RR of MD and CV in right hand was excellent in the beginning and middle stages, and fair in the exhaustion one, showing decreasing reliability as fatigue increases. In the left hand RR of MD and CV was generally lower. MD showed excellent reliability in the beginning stage and good reliability in the other stages. CV showed fair relative reliability at both beginning and middle stages, excellent in the last one. Conversely, it was observed high AR of MD and CV in all stages in both hands.

Conclusions

All indices are reliable to assess motor control of thumb-index pinch in both hands.

Impaired Hand Dexterity Function in a Non-human Primate Model with Chronic Parkinson's Disease

Symptoms of Parkinson’s disease (PD) caused by loss of dopaminergic neurons are accompanied by movement disorders, including tremors, rigidity, bradykinesia, and akinesia. Non-human primate (NHP) models with PD play an essential role in the analysis of PD pathophysiology and behavior symptoms. As impairments of hand dexterity function can affect activities of daily living in patients with PD, research on hand dexterity function in NHP models with chronic PD is essential. Traditional rating scales previously used in the evaluation of animal spontaneous behavior were insufficient due to factors related to subjectivity and passivity. Thus, experimentally designed applications for an appropriate apparatus are necessary. In this study, we aimed to longitudinally assess hand dexterity function using hand dexterity task (HDT) in NHP-PD models. To validate this assessment, we analyzed the alteration in Parkinsonian tremor signs and the functionality of presynaptic dopaminergic neuron using positron emission tomography imaging of dopamine transporters in these models. In addition, a significant inverse correlation between HDT and DAT level was identified, but no local bias was found. The correlation with intention tremor signs was lower than the resting tremor. In conclusion, the evaluation of HDT may reflect behavioral symptoms of NHP-PD models. Furthermore, HDT was effectively used to experimentally distinguish intention tremors from other tremors.

Effects of Transcranial Direct Current Stimulation Over the Dorsolateral Prefrontal Cortex (PFC) on Cognitive-Motor Dual Control Skills

This randomized crossover study investigated whether anodal transcranial direct current stimulation (tDCS) over the dorsolateral prefontal cortex (dlPFC) modulates memory-guided finger isometric maintenance during single motor and dual cognitive-motor tasks, based on electroencephalogram (EEG) signals. Twenty-three healthy participants (14 female; M age = 29.130 years, SD = 10.918) underwent both sham and 2-mA stimulation sessions over the dlPFC for 20 minutes, with a minimum washout period of seven days. We analyzed finger-force isometric maintenance and event-related spectral perturbation (ERSP) of the EEG during early and later phases of both tasks. We observed a significant motor accuracy improvement (p = .014) and significant variation of force output (p = .027) with significant decrease in ERSP on the dorsomedial prefrontal cortex (dmPFC) (early phase, p = .027; later phase, p = .023) only after 2 mA stimulation. Thus, anodal tDCS over the dlPFC may improve memory-guided force control during cognitive-motor dual tasks.

Effects of the Surface Texture and Weight of a Pinch Apparatus on the Reliability and Validity of a Hand Sensorimotor Control Assessment

OBJECTIVES

To investigate the reliability and validity of a modified pinch apparatus devised with 3 surface textures and 2 different weights for clinical application.

DESIGN

Case-controlled study.

SETTING

A university hospital.

PARTICIPANTS

The participants (N=32) included carpal tunnel syndrome (CTS) patients (n=16) with 20 sensory neuropathy hands, and an equal number of age-sex matched volunteers without CTS, as well as young volunteers without CTS (n=16 with 20 hands) used to analyze both the testing validity and reliability of the modified device.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The Semmes-Weinstein monofilament (SWM) and two-point discrimination (2PD) tests were conducted, and the force ratio between the FP_peak (peak pinch force during lifting phase) and FL_max (maximum load force at maximum upward acceleration onset) detected from a pinch-holding-up activity (PHUA) under various testing conditions was obtained.

RESULTS

The range of the intraclass correlation coefficient of this pinch device was 0.369-0.952. The CTS patients exhibited poorer force modulation ability according to the inertial change in a dynamic lifting task when compared to the controls under all testing conditions (P<.001). The area under the receiver operating characteristic force ratio curve was 0.841, revealing high accuracy of the test for diagnosing CTS neuropathic hands under the testing condition in which the 125-g coarse texture device was used. In addition, the weight factor was shown to have significant effects on the sensitivity and accuracy of the PHUA assessment.

CONCLUSIONS

This study showed that the PHUA test via the modified pinch apparatus is a sensitive tool that can be used in clinical practice for detecting neuropathic CTS hands. In addition, changing the weight of the pinch device has a significant effect on the sensitivity and accuracy of the PHUA assessment.

Effects of Transcranial Direct Current Stimulation (tDCS) Over the Frontal Polar Area on Motor and Executive Functions in Parkinson's Disease; A Pilot Study

Parkinson's disease (PD) is a neurodegenerative disorder with motor and non-motor symptoms due to degeneration of dopaminergic neurons. The current pharmacological treatments induce complications associated with long-term use. However, current stimulation techniques for PD treatment, such as deep brain stimulation (DBS), are too invasive. In this context, non-invasive brain stimulation including transcranial direct current stimulation (tDCS) may be a safe and effective alternative treatment for PD. We previously reported that anodal tDCS over the frontal polar area (FPA) improved motor functions in heathy subjects. Therefore, in the present study, effects of tDCS over the FPA on motor and cognitive functions of PD patients were analyzed. Nine PD patients (3 men and 6 women) participated in this cross over study with three tDCS protocols; anodal, cathodal or sham tDCS over the FPA. Each tDCS protocol was applied for 1 week (5 times/week). Before and after each protocol, motor and cognitive functions of the patients were assessed using Unified PD Rating Scale [UPDRS (part III: motor examination)], Fugl Meyer Assessment set (FMA), Simple Test for Evaluating hand Function (STEF) and Trail Making Test A (TMT-A). The results indicated that anodal stimulation significantly decreased scores of motor disability in UPDRS-III compared with sham and cathodal stimulation, and significantly increased scores of motor functions in FMA compared with sham stimulation. Furthermore, anodal stimulation significantly decreased time to complete a motor task requiring high dexterity in STEF compared with those requiring low and medium levels of dexterity. In addition, anodal stimulation significantly decreased time to complete the TMT-A task, which requires executive functions, compared with sham stimulation. To the best of our knowledge, this is the first clinical research reporting that tDCS over the FPA successfully improved the motor and non-motor functions in PD patients. These findings suggest that tDCS over the FPA might be a useful alternative for the treatment of PD patients.

Quantitative assessment of hand motor function in cervical spinal disorder patients using target tracking tests

Cervical spondylotic myelopathy (CSM) is a chronic spinal disorder in the neck region. Its prevalence is growing rapidly in developed nations, creating a need for an objective assessment tool. This article introduces a system for quantifying hand motor function using a handgrip device and target tracking test. In those with CSM, hand motor impairment often interferes with essential daily activities. The analytic method applied machine learning techniques to investigate the efficacy of the system in (1) detecting the presence of impairments in hand motor function, (2) estimating the perceived motor deficits of CSM patients using the Oswestry Disability Index (ODI), and (3) detecting changes in physical condition after surgery, all of which were performed while ensuring test-retest reliability. The results based on a pilot data set collected from 30 patients with CSM and 30 nondisabled control subjects produced a c-statistic of 0.89 for the detection of impairments, Pearson r of 0.76 with p < 0.001 for the estimation of ODI, and a c-statistic of 0.82 for responsiveness. These results validate the use of the presented system as a means to provide objective and accurate assessment of the level of impairment and surgical outcomes.

Quantitative Assessment of Hand Dysfunction in Patients with Early Parkinson's Disease and Focal Hand Dystonia

Objective

Motor impairments related to hand function are common symptoms in patients with movement disorders, such as Parkinson’s disease (PD) and focal hand dystonia (FHD). However, hand dysfunction has not been quantitatively assessed as a clinical tool for screening patient groups from healthy controls (HCs). The aim of our study was 1) to quantitatively assess hand dysfunction in patients with PD and FHD and its usefulness as a screening tool 2) to grade disease severity in PD and FHD based on hand dysfunction.

Methods

The current case-control study included HCs (n = 50) and patients with known history of PD (n = 25) or FHD (n = 16). Hand function was assessed by a precision grip task while participants lifted objects of 1.3 N and 1.7 N under dry skin conditions, followed by very wet skin conditions (VWSCs). Receiver operating characteristic and summative scoring analyses were performed.

Results

In PD, the combination of loading phase duration and lifting phase duration at quantitative cutoffs of 0.36 and 0.74 seconds identified 21/25 patients as diseased and 49/50 subjects as HCs with 1.7 N under VWSCs. In PD, 5/21 was graded as “mild” and 16/21 as “moderate cases.” In FHD, slip force at a cutoff of 1.2 N identified 13/16 patients as diseased and 41/50 subjects as HC with 1.7 N under VWSCs, but disease severity could not be graded.

Conclusion

Our results demonstrate the use of precision grip task as an important clinical tool in assessment of hand dysfunction in movement disorder patients. Use of quantitative cutoffs may improve diagnostic accuracy and serve as a valuable adjunct to existing clinical assessment methods.

Rehabilitation of hand function after spinal cord injury using a novel handgrip device: a pilot study

Background

Activity-based therapy (ABT) for patients with spinal cord injury (SCI), which consists of repetitive use of muscles above and below the spinal lesion, improves locomotion and arm strength. Less data has been published regarding its effects on hand function. We sought to evaluate the effects of a weekly hand-focused therapy program using a novel handgrip device on grip strength and hand function in a SCI cohort.

Methods

Patients with SCI were enrolled in a weekly program that involved activities with the MediSens (Los Angeles, CA) handgrip. These included maximum voluntary contraction (MVC) and a tracking task that required each subject to adjust his/her grip strength according to a pattern displayed on a computer screen. For the latter, performance was measured as mean absolute accuracy (MAA). The Spinal Cord Independence Measure (SCIM) was used to measure each subject’s independence prior to and after therapy.

Results

Seventeen patients completed the program with average participation duration of 21.3 weeks. The cohort included patients with American Spinal Injury Association (ASIA) Impairment Scale (AIS) A (n = 12), AIS B (n = 1), AIS C (n = 2), and AIS D (n = 2) injuries. The average MVC for the cohort increased from 4.1 N to 21.2 N over 20 weeks, but did not reach statistical significance. The average MAA for the cohort increased from 9.01 to 21.7% at the end of the study (p = .02). The cohort’s average SCIM at the end of the study was unchanged compared to baseline.

Conclusions

A weekly handgrip-based ABT program is feasible and efficacious at increasing hand task performance in subjects with SCI.

Bilateral adaptive deep brain stimulation is effective in Parkinson's disease

INTRODUCTION & OBJECTIVES

Adaptive deep brain stimulation (aDBS) uses feedback from brain signals to guide stimulation. A recent acute trial of unilateral aDBS showed that aDBS can lead to substantial improvements in contralateral hemibody Unified Parkinson's Disease Rating Scale (UPDRS) motor scores and may be superior to conventional continuous DBS in Parkinson's disease (PD). We test whether potential benefits are retained with bilateral aDBS and in the face of concurrent medication.

METHODS

We applied bilateral aDBS in 4 patients with PD undergoing DBS of the subthalamic nucleus. aDBS was delivered bilaterally with independent triggering of stimulation according to the amplitude of β activity at the corresponding electrode. Mean stimulation voltage was 3.0±0.1 volts. Motor assessments consisted of double-blinded video-taped motor UPDRS scores that included both limb and axial features.

RESULTS

UPDRS scores were 43% (p=0.04; Cohen's d=1.62) better with aDBS than without stimulation. Motor improvement with aDBS occurred despite an average time on stimulation (ToS) of only 45%. Levodopa was well tolerated during aDBS and led to further reductions in ToS.

CONCLUSION

Bilateral aDBS can improve both axial and limb symptoms and can track the need for stimulation across drug states.

DJ-1 protects against undernutrition-induced atrophy through inhibition of the MAPK-ubiquitin ligase pathway in myoblasts

AIMS

The purpose of this study is to explore whether antioxidant DJ-1 protein affects the atrophy of skeletal muscle cell induced by undernutrition.

MAIN METHODS

To determine cell atrophic responses, L6 cell line and skeletal primary cells from mouse hind limbs were cultivated under condition of FBS-free and low glucose. Changes of protein expression were analyzed using Western blot. Overexpression and knockdown of DJ-1 was performed in cells to assess its influence on cell atrophic responses.

KEY FINDINGS

Undernutrition decreased cell size and increased the abundance of oxidized form and total form of DJ-1 protein in L6 myoblasts. The undernourished cells revealed an elevation in the expression of muscle-specific RING finger-1 (MuRF-1) and atrogin-1, and in the phosphorylations of p38 mitogen-activated protein kinase (MAPK) and stress-activated protein kinase/c-Jun N-terminal kinase compared with control groups. Moreover, DJ-1-knockout mice showed a decrease in cell size and an enhancement in the expression of MuRF-1 and atrogin-1, as well as in the phosphorylation of MAPKs in gastrocnemius muscles; these changes were also observed in L6 cells transfected with siRNA of DJ-1. On the other hand, L6 cells overexpressing full-length DJ-1 did not exhibit the alterations in cell size and ubiquitin ligases seen after undernourished states of control cells. Myotubes differentiated from L6 cells also showed elevated expression of MuRF-1 and atrogin-1 in response to undernutrition.

SIGNIFICANCE

These results suggest that DJ-1 protein may contribute to undernutrition-induced atrophy via MAPKs/ubiquitin ligase pathway in skeletal muscle cells.

A Prediction Model for Functional Outcomes in Spinal Cord Disorder Patients Using Gaussian Process Regression

Predicting the functional outcomes of spinal cord disorder patients after medical treatments, such as a surgical operation, has always been of great interest. Accurate posttreatment prediction is especially beneficial for clinicians, patients, care givers, and therapists. This paper introduces a prediction method for postoperative functional outcomes by a novel use of Gaussian process regression. The proposed method specifically considers the restricted value range of the target variables by modeling the Gaussian process based on a truncated Normal distribution, which significantly improves the prediction results. The prediction has been made in assistance with target tracking examinations using a highly portable and inexpensive handgrip device, which greatly contributes to the prediction performance. The proposed method has been validated through a dataset collected from a clinical cohort pilot involving 15 patients with cervical spinal cord disorder. The results show that the proposed method can accurately predict postoperative functional outcomes, Oswestry disability index and target tracking scores, based on the patient's preoperative information with a mean absolute error of 0.079 and 0.014 (out of 1.0), respectively.

Utilization of a novel digital measurement tool for quantitative assessment of upper extremity motor dexterity: a controlled pilot study

Background

The current methods of assessing motor function rely primarily on the clinician’s judgment of the patient’s physical examination and the patient’s self-administered surveys. Recently, computerized handgrip tools have been designed as an objective method to quantify upper-extremity motor function. This pilot study explores the use of the MediSens handgrip as a potential clinical tool for objectively assessing the motor function of the hand.

Methods

Eleven patients with cervical spondylotic myelopathy (CSM) were followed for three months. Eighteen age-matched healthy participants were followed for two months. The neuromotor function and the patient-perceived motor function of these patients were assessed with the MediSens device and the Oswestry Disability Index respectively. The MediSens device utilized a target tracking test to investigate the neuromotor capacity of the participants. The mean absolute error (MAE) between the target curve and the curve tracing achieved by the participants was used as the assessment metric. The patients’ adjusted MediSens MAE scores were then compared to the controls. The CSM patients were further classified as either “functional” or “nonfunctional” in order to validate the system’s responsiveness. Finally, the correlation between the MediSens MAE score and the ODI score was investigated.

Results

The control participants had lower MediSens MAE scores of 8.09%±1.60%, while the cervical spinal disorder patients had greater MediSens MAE scores of 11.24%±6.29%. Following surgery, the functional CSM patients had an average MediSens MAE score of 7.13%±1.60%, while the nonfunctional CSM patients had an average score of 12.41%±6.32%. The MediSens MAE and the ODI scores showed a statistically significant correlation (r=-0.341, p<1.14×10^-5). A Bland-Altman plot was then used to validate the agreement between the two scores. Furthermore, the percentage improvement of the the two scores after receiving the surgical intervention showed a significant correlation (r=-0.723, p<0.04).

Conclusions

The MediSens handgrip device is capable of identifying patients with impaired motor function of the hand. The MediSens handgrip scores correlate with the ODI scores and may serve as an objective alternative for assessing motor function of the hand.

Electronic supplementary material

The online version of this article (doi:10.1186/1743-0003-11-121) contains supplementary material, which is available to authorized users.

Effect of dual-task interference on the hand flexibility of patients with Parkinson's disease carrying the leucine-rich repeat kinase 2 gene mutation

The aim of the present study was to observe the changes in hand flexibility of patients with Parkinson's disease (PD) and the effect of dual-task interference. Patients with PD were distributed into two subgroups: the leucine-rich repeat kinase 2 (LRRK2) mutation PD (LRRK2⁺) and the LRRK2 mutation-free (LRRK2^-) PD groups. The healthy controls were distributed into two subgroups: the LRRK2⁺ control and the LRRK2^- control groups. The first task was the Purdue pegboard test. The second task was to perform serial seven subtractions. Single-task and dual-task tests were performed, respectively. The numbers of pegs inserted with the dominant hand, non-dominant hand and both hands in the pegboard test and the number of correct responses in the serial seven subtractions test within 30 sec were recorded. The United Parkinson's Disease Rating Scale (UPDRS) III score of examinees in the LRRK2⁺ PD group was significantly higher than that of examinees in the LRRK2^- PD group (P<0.05). The number of pegs inserted within 30 sec by patients with PD was significantly lower than that by the controls (P<0.05). The indicators of patients with PD, including number of variation in the subtraction test score when the dominant-hand was used in the pegboard test (NVD), number of variation in the subtraction test score when the non-dominant hand was used in the pegboard test (NVND) and number of variation in the subtraction test score when the both-hand was used in the pegboard test (NVB), were significantly different compared with those of the control group (P<0.05). The difference in the number of correct responses within 30 sec of patients with PD was significantly correlated with the UPDRSIII score (P<0.05). In conclusion, the hand flexibility of patients with PD was markedly lower than that of the controls. When both tasks were performed, the ability markedly decreased in the second cognitive task, particularly in the LRRK2⁺ PD group.

Management of upper extremity dysfunction in people with Parkinson disease and Huntington disease: facilitating outcomes across the disease lifespan

Parkinson Disease (PD) and Huntington Disease (HD) are degenerative neurological diseases, which can result in impairments and activity limitations affecting the upper extremities from early in the disease process. The progressive nature of these diseases poses unique challenges for therapists aiming to effectively maximize physical functioning and minimize participation restrictions in these patient groups. Research is underway in both diseases to develop effective disease-modifying agents and pharmacological interventions, as well as mobility-focused rehabilitation protocols. Rehabilitation, and in particular task-specific interventions, has the potential to influence the upper extremity functional abilities of patients with these degenerative conditions. However to date, investigations of interventions specifically addressing upper extremity function have been limited in both PD, and in particular HD. In this paper, we provide an update of the known pathological features of PD and HD as they relate to upper extremity function. We further review the available literature on the use of outcome measures, and the clinical management of upper extremity function in both conditions. Due to the currently limited evidence base in both diseases, we recommend utilization of a clinical management framework specific for degenerative conditions that can serve as a guideline for disease management.

Bimanual force coordination in Parkinson's disease patients with bilateral subthalamic deep brain stimulation

OBJECTIVE

Studies of bimanual actions similar to activities of daily living (ADLs) are currently lacking in evaluating fine motor control in Parkinson's disease patients implanted with bilateral subthalamic deep brain stimulators. We investigated basic time and force characteristics of a bimanual task that resembles performance of ADLs in a group of bilateral subthalamic deep brain stimulation (DBS) patients.

METHODS

Patients were evaluated in three different DBS parameter conditions off stimulation, on clinically derived stimulation parameters, and on settings derived from a patient-specific computational model. Model-based parameters were computed as a means to minimize spread of current to non-motor regions of the subthalamic nucleus via Cicerone Deep Brain Stimulation software. Patients were evaluated off parkinsonian medications in each stimulation condition.

RESULTS

The data indicate that DBS parameter state does not affect most aspects of fine motor control in ADL-like tasks; however, features such as increased grip force and grip symmetry varied with the stimulation state. In the absence of DBS parameters, patients exhibited significant grip force asymmetry. Overall UPDRS-III and UPDRS-III scores associated with hand function were lower while patients were experiencing clinically-derived or model-based parameters, as compared to the off-stimulation condition.

CONCLUSION

While bilateral subthalamic DBS has been shown to alleviate gross motor dysfunction, our results indicate that DBS may not provide the same magnitude of benefit to fine motor coordination.

Cognitive deficits in a mouse model of pre-manifest Parkinson's disease

Early cognitive deficits are increasingly recognized in patients with Parkinson's disease (PD), and represent an unmet need for the treatment of PD. These early deficits have been difficult to model in mice, and their mechanisms are poorly understood. α-Synuclein is linked to both familial and sporadic forms of PD, and is believed to accumulate in brains of patients with PD before cell loss. Mice expressing human wild-type α-synuclein under the Thy1 promoter (Thy1-aSyn mice) exhibit broad overexpression of α-synuclein throughout the brain and dynamic alterations in dopamine release several months before striatal dopamine loss. We now show that these mice exhibit deficits in cholinergic systems involved in cognition, and cognitive deficits in domains affected in early PD. Together with an increase in extracellular dopamine and a decrease in cortical acetylcholine at 4-6 months of age, Thy1-aSyn mice made fewer spontaneous alternations in the Y-maze and showed deficits in tests of novel object recognition (NOR), object-place recognition, and operant reversal learning, as compared with age-matched wild-type littermates. These data indicate that cognitive impairments that resemble early PD manifestations are reproduced by α-synuclein overexpression in a murine genetic model of PD. With high power to detect drug effects, these anomalies provide a novel platform for testing improved treatments for these pervasive cognitive deficits.

Children with heavy prenatal alcohol exposure exhibit deficits when regulating isometric force

BACKGROUND

Production of isometric (i.e., constant) force is an essential component of performing everyday functional tasks, yet no studies have investigated how this type of force is regulated in children with confirmed histories of heavy prenatal alcohol exposure.

METHODS

Children 7 to 17 years old with heavy prenatal alcohol exposure (n = 25) and without exposure (n = 18) applied force to a load cell to generate an isometric force that matched a criterion target force displayed on a computer monitor. Two levels of target force were investigated in combination with 3 levels of visual feedback frequency that appeared on the computer monitor as a series of yellow dots. Force was maintained for 20 seconds and participants completed 6 trials per test condition.

RESULTS

Root-mean-square error, signal-to-noise ratio, and sample entropy indexed response accuracy, response variability, and signal complexity, respectively. The analyses revealed that in comparison with controls, children with gestational ethanol exposure were significantly less accurate and more variable in regulating their force output and generated a response signal with greater regularity and less complexity in the time domain.

CONCLUSIONS

Children with prenatal alcohol exposure experience significant deficits in isometric force production that may impede their ability to perform basic motor skills and activities in everyday tasks.

A review of dual-task walking deficits in people with Parkinson's disease: motor and cognitive contributions, mechanisms, and clinical implications

Gait impairments in Parkinson's disease (PD) are exacerbated under dual-task conditions requiring the simultaneous performance of cognitive or motor tasks. Dual-task walking deficits impact functional mobility, which often requires walking while performing concurrent tasks such as talking or carrying an object. The consequences of gait impairments in PD are significant and include increased disability, increased fall risk, and reduced quality of life. However, effective therapeutic interventions for dual-task walking deficits are limited. The goals of this narrative review are to describe dual-task walking deficits in people with PD, to discuss motor and cognitive factors that may contribute to these deficits, to review potential mechanisms underlying dual-task deficits, and to discuss the effect of therapeutic interventions on dual-task walking deficits in persons with PD.

Young and middle-aged rats exhibit isometric forelimb force control deficits in a model of early-stage Parkinson's disease

Deficits in manual motor control often accompany the early stages of Parkinson's disease (PD), and are often revealed through isometric force tasks. In order to determine whether similar deficits occur in a rat model of early-stage PD, young (8 months) and middle-aged (18 months) rats were trained to produce sustained press-hold-release isometric forelimb responses that allowed for analyses of force output and spectral analysis of forelimb stability and tremor. Rats then received a 6-hydroxydopamine (6-OHDA) infusion into the striatum contralateral to the trained forelimb and were tested for 4 weeks post-lesion. The resulting partial striatal dopamine depletions (which at 41±12% and 43±6% in young and middle-aged rats, respectively, did not differ between the two groups) resulted in isometric forelimb deficits. Specifically, rats exhibited significantly diminished force stability and increased high frequency (10-25Hz) tremor, indicating potential postural disturbances and increased postural tremor, respectively. Durations of press-hold-release bouts were also increased post-lesion, suggesting difficulty in task disengagement. Despite pre-lesion differences in some of the force measures, the effects of partial nigrostriatal DA depletion did not differ between the two age groups. These results support the use of the press-while-licking task in preclinical studies modeling isometric force control deficits in PD.

Preliminary investigation of test-retest reliability of a robotic assessment for Parkinson's disease

Several systems have been proposed to objectively quantify the motor signs of Parkinson's disease. While validity has been investigated for a subset of these systems, test-retest reliability of automated assessments has been more neglected. We have created a protocol that uses a robotic system to measure force and position as the user performs tracking tasks with and without a simultaneous cognitive or motor task. We present preliminary results for test-retest reliability with eight individuals with early to moderate PD. Based on this data, we identified variables with large, significant correlations between the test and retest data. A total of 21 reliable variables were identified with all portions of the assessment protocol producing reliable variables.

Application of modified regression techniques to a quantitative assessment for the motor signs of Parkinson's disease

Effective clinical trials for neuroprotective interventions for Parkinson's disease (PD) require a way to quantify an individual's motor symptoms and analyze the change in these symptoms over time. Clinical scales provide a global picture of function but cannot precisely measure specific aspects of motor control. We have used commercially available sensors to create a protocol called Advanced Sensing for Assessment of Parkinson's disease (ASAP) to obtain a quantitative and reliable measure of motor impairment in early to moderate PD. The ASAP protocol measures grip force as an individual tracks a sinusoidal or pseudorandom target force under three conditions of increasing cognitive load. Thirty individuals with PD have completed the ASAP protocol. The ASAP data for 26 of these individuals were summarized in terms of 36 variables, and modified regression techniques were used to predict an individual's score on the Unified Parkinson Disease Rating Scale based on ASAP data. We observed a mean prediction error of approximately 3.5 UPDRS points, and the predicted score accounted for approximately 76% of the variability of the UPDRS. These results demonstrate that the ASAP protocol can measure differences for individuals who are clinically different. This indicates that the ASAP protocol may be able to measure changes with time in the motor signs of an individual with PD.