Changes in corticospinal drive to spinal motoneurones following tablet-based practice of manual dexterity

The application of heating film to hands reduces the decline in manual dexterity performance associated with cold exposure

PURPOSE

Exposure to cold temperatures decreases finger temperature (Tfing) and dexterity. Decreased manual function and dexterity can be serious safety risks, especially in tasks that require fine motor movements that must be performed outdoors. The aim of this study was to determine whether hand heating with a minimal power requirement (14.8 W) results in a smaller reduction in Tfing and manual dexterity performance during mild cold exposure compared to a non-heated control condition.

METHODS

In a randomized crossover design, twenty-two healthy participants were exposed to a moderately cold environment (5  ºC) for 90 min. One condition had no intervention (CON), while the other had the palmar and dorsal hands heated (HEAT) by using electric heating films. Tfing and cutaneous vascular conductance (CVC) were continuously monitored using laser Doppler flowmetry. Manual dexterity performance and cognitive function were assessed by the Grooved Pegboard Test (GPT) and Stroop Color-Word (SCW) test, respectively, during the baseline period and every 30 min during the cold exposure.

RESULTS

After the cold exposure, Tfing was higher in HEAT relative to CON (CON 9.8 vs. HEAT 13.7 ºC, p < 0.0001). GPT placing time, as an index of dexterity performance, was also shorter in HEAT by 14.5% (CON 69.10 ± 13.08 vs. HEAT 59.06 ± 7.99 s, p < 0.0001). There was no difference in CVC between the two conditions during the cold exposure (p > 0.05 for all). Cognitive function was similar between two conditions (p > 0.05 for all).

CONCLUSION

The proposed hand heating method offers a practical means of heating fingers to maintain dexterity throughout prolonged cold exposure.

Influencing factors of corticomuscular coherence in stroke patients

Stroke, also known as cerebrovascular accident, is an acute cerebrovascular disease with a high incidence, disability rate, and mortality. It can disrupt the interaction between the cerebral cortex and external muscles. Corticomuscular coherence (CMC) is a common and useful method for studying how the cerebral cortex controls muscle activity. CMC can expose functional connections between the cortex and muscle, reflecting the information flow in the motor system. Afferent feedback related to CMC can reveal these functional connections. This paper aims to investigate the factors influencing CMC in stroke patients and provide a comprehensive summary and analysis of the current research in this area. This paper begins by discussing the impact of stroke and the significance of CMC in stroke patients. It then proceeds to elaborate on the mechanism of CMC and its defining formula. Next, the impacts of various factors on CMC in stroke patients were discussed individually. Lastly, this paper addresses current challenges and future prospects for CMC.

Effects of noninvasive neuromodulation targeting the spinal cord on early learning of force control by the digits

AIMS

Control of finger forces underlies our capacity for skilled hand movements acquired during development and reacquired after neurological injury. Learning force control by the digits, therefore, predicates our functional independence. Noninvasive neuromodulation targeting synapses that link corticospinal neurons onto the final common pathway via spike-timing-dependent mechanisms can alter distal limb motor output on a transient basis, yet these effects appear subject to individual differences. Here, we investigated how this form of noninvasive neuromodulation interacts with task repetition to influence early learning of force control during precision grip.

METHODS

The unique effects of neuromodulation, task repetition, and neuromodulation coinciding with task repetition were tested in three separate conditions using a within-subject, cross-over design (n = 23).

RESULTS

We found that synchronizing depolarization events within milliseconds of stabilizing precision grip accelerated learning but only after accounting for individual differences through inclusion of subjects who showed upregulated corticospinal excitability at 2 of 3 time points following conditioning stimulation (n = 19).

CONCLUSIONS

Our findings provide insights into how the state of the corticospinal system can be leveraged to drive early motor skill learning, further emphasizing individual differences in the response to noninvasive neuromodulation. We interpret these findings in the context of biological mechanisms underlying the observed effects and implications for emerging therapeutic applications.

[Effectiveness of a tablet telerehabilitation application in patients with distal radius fracture]

INTRODUCTION

To assess whether, in patients with distal radius fracture feedback-guided exercises performed on a tablet touchscreen reduce healthcare usage and improve clinical recovery, more than the conventional home exercise program prescribed on paper.

MATERIAL AND METHODS

A multicentre, parallel, two-group, pragmatic, controlled trial with assessor blinding and intention-to-treat analysis. Forty-six patients with distal radius fracture were recruited in Andalusian Public Health System. Participants in the experimental and control groups received the same in-patient physiotherapy sessions. Experimental group received a home exercise program using the ReHand tablet application and control group received an evidence-based home exercise program on paper. The primary outcome was the number of physiotherapy sessions tallied from hospitals data management system. Secondary outcomes included: the face-to-face rehabilitation consultations with a physiatrist, and clinical outcomes such as functional ability, grip strength, dexterity, pain intensity and range of motion.

RESULTS

The experimental group required fewer physiotherapy sessions (MD: -16.94; 95%CI: -32.5 to -1.38) and rehabilitation consultations (MD: -1.7; 95%CI: -3.39 to -0.02) compared to the control group.

CONCLUSIONS

In patients with distal radius fracture, prescribing feedback-guided exercises performed on a tablet touchscreen provided by ReHand reduced number of physiotherapy sessions and rehabilitation consultations.

Effects of dynamic and isometric motor practice on position control, force control and corticomuscular coherence in preadolescent children

In this study, we investigated the effects of motor practice with an emphasis on either position or force control on motor performance, motor accuracy and variability in preadolescent children. Furthermore, we investigated corticomuscular coherence and potential changes following motor practice. We designed a setup allowing discrete wrist flexions of the non-dominant hand and tested motor accuracy and variability when the task was to generate specific movement endpoints (15-75 deg) or force levels (5-25% MVC). All participants were tested in both tasks at baseline and post motor practice without augmented feedback on performance. Following baseline assessment, participants (44 children aged 9-11 years) were randomly assigned to either position (PC) or force control (FC) motor practice or a resting control group (CON). The PC and FC groups performed four blocks of 40 trials motor practice with augmented feedback on performance. Following practice, improvements in movement accuracy were significantly greater in the PC group compared to the FC and CON groups (p < 0.001). None of the groups displayed changes in force task performance indicating no benefits of force control motor practice and low transfer between tasks (p-values:0.08-0.45). Corticomuscular coherence (C4-FCR) was demonstrated during the hold phase in both tasks with no difference between tasks. Corticomuscular coherence did not change from baseline to post practice in any group. Our findings demonstrate that preadolescent children improve position control following dynamic accuracy motor practice. Contrary to previous findings in adults, preadolescent children displayed smaller or no improvements in force control following isometric motor practice, low transfer between tasks and no changes in corticomuscular coherence.

Effectiveness of a Telerehabilitation Evidence-Based Tablet App for Rehabilitation in Traumatic Bone and Soft Tissue Injuries of the Hand, Wrist, and Fingers

OBJECTIVE

To assess whether feedback-guided exercises performed on a tablet touchscreen improve clinical recovery and reduce health care usage more than the conventional home exercise program prescribed on paper in patients with bone and soft tissue injuries of the wrist, hand, and/or fingers treated by public health services.

DESIGN

A multicenter assessor-blinded, parallel, 2-group controlled trial.

SETTING

Trauma and rehabilitation services of 4 hospitals.

PARTICIPANTS

Six hundred sixty-three patients with limited functional ability due to bone and soft tissue injuries of the wrist, hand, and/or fingers (N=663).

INTERVENTIONS

The experimental group received a home exercise program using a tablet-based application with feedback, monitoring, and progression; the control group received an evidence-based home exercise program on paper.

MAIN OUTCOME MEASURES

The primary outcome was functional ability through Patient Rated Wrist Evaluation for wrist conditions and the short version of Disabilities of the Arm, Shoulder and Hand for all other hand pathologies. Secondary outcomes included dexterity, pain intensity, grip strength, and health care usage (number of patients referred to rehabilitation service and number of clinical appointments).

RESULTS

The experimental group showed a significant improvement on the Patient Rated Wrist Evaluation (P=.001) and the short version of Disabilities of the Arm, Shoulder and Hand (P=.001) with medium effect sizes (η²=0.066-0.067) when compared with the control group. Regarding health care usage, the experimental group presented a reduction of 41% in the rate of referrals to face-to-face rehabilitation service consultations, a reduction of rehabilitation consultations (mean difference=-1.64; 95% confidence interval, -2.64 to -0.65) and physiotherapy sessions (mean difference=-8.52, 95% confidence interval, -16.92 to -0.65) compared to the control group.

CONCLUSIONS

In patients with bone and soft tissue injuries of the wrist, hand, and/or fingers, prescribing feedback-guided exercises performed on a tablet touchscreen was more effective for improving patients' functional ability and reduced the number of patients referred to rehabilitation consultation and number of clinical appointments.

Dynamic motor practice improves movement accuracy, force control and leads to increased corticospinal excitability compared to isometric motor practice

The central nervous system has a remarkable ability to plan motor actions, to predict and monitor the sensory consequences during and following motor actions and integrate these into future actions. Numerous studies investigating human motor learning have employed tasks involving either force control during isometric contractions or position control during dynamic tasks. To our knowledge, it remains to be elucidated how motor practice with an emphasis on position control influences force control and vice versa. Furthermore, it remains unexplored whether these distinct types of motor practice are accompanied by differential effects on corticospinal excitability. In this study, we tested motor accuracy and effects of motor practice in a force or position control task allowing wrist flexions of the non-dominant hand in the absence of online visual feedback. For each trial, motor performance was quantified as errors (pixels) between the displayed target and the movement endpoint. In the main experiment, 46 young adults were randomized into three groups: position control motor practice (PC), force control motor practice (FC), and a resting control group (CON). Following assessment of baseline motor performance in the position and force control tasks, intervention groups performed motor practice with, augmented visual feedback on performance. Motor performance in both tasks was assessed following motor practice. In a supplementary experiment, measures of corticospinal excitability were obtained in twenty additional participants by application of transcranial magnetic stimulation to the primary motor cortex hot spot of the flexor carpi radialis muscle before and following either position or force control motor practice. Following motor practice, accuracy in the position task improved significantly more for PC compared to FC and CON. For the force control task, both the PC and FC group improved more compared to CON. The two types of motor practice thus led to distinct effects including positive between-task transfer accompanying dynamic motor practice The results of the supplementary study demonstrated an increase in corticospinal excitability following dynamic motor practice compared to isometric motor practice. In conclusion, dynamic motor practice improves movement accuracy, and force control and leads to increased corticospinal excitability compared to isometric motor practice.

Reorganization of functional and directed corticomuscular connectivity during precision grip from childhood to adulthood

How does the neural control of fine movements develop from childhood to adulthood? Here, we investigated developmental differences in functional corticomuscular connectivity using coherence analyses in 111 individuals from four different age groups covering the age range 8–30 y. EEG and EMG were recorded while participants performed a uni-manual force-tracing task requiring fine control of force in a precision grip with both the dominant and non-dominant hand. Using beamforming methods, we located and reconstructed source activity from EEG data displaying peak coherence with the EMG activity of an intrinsic hand muscle during the task. Coherent cortical sources were found anterior and posterior to the central sulcus in the contralateral hemisphere. Undirected and directed corticomuscular coherence was quantified and compared between age groups. Our results revealed that coherence was greater in adults (20–30 yo) than in children (8–10 yo) and that this difference was driven by greater magnitudes of descending (cortex-to-muscle), rather than ascending (muscle-to-cortex), coherence. We speculate that the age-related differences reflect maturation of corticomuscular networks leading to increased functional connectivity with age. We interpret the greater magnitude of descending oscillatory coupling as reflecting a greater degree of feedforward control in adults compared to children. The findings provide a detailed characterization of differences in functional sensorimotor connectivity for individuals at different stages of typical ontogenetic development that may be related to the maturational refinement of dexterous motor control.

Intramuscular Coherence of the Lower Flexor Muscles during Robotic Ankle-Assisted Gait

A close-fitting assisted walking device (RE-Gait) designed to assist ankle movements might be a novel approach for acquiring the forefoot rocker function in the gait cycle. The purpose of the present study was to investigate the effects of using RE-Gait by evaluating the intramuscular coherence (IMC) of the two parts of the tibialis anterior muscles (TA), which could indicate whether a common synaptic drive is present. Seventeen healthy volunteers walked on a treadmill at a comfortable speed before, during, and immediately after 15-minute RE-Gait intervention. After RE-Gait intervention, IMC of the two parts of the TA muscles in the beta frequency band in the initial swing phase was significantly enhanced during RE-Gait intervention. In addition, IMCs in the beta and low-gamma frequency bands were significantly correlated with the enhancement ratio of the step length. These results suggest that robotic ankle plantar flexion and dorsiflexion assistance in the initial swing phase may be effective for improving gait function with enhancement of the functioning of the sensorimotor loop.

Dexteria app. therapy versus conventional hand therapy in stroke

Purpose

Hand impairment post-stroke is a very common and important rehabilitation goal for functional independence. Advanced therapy options such as an app. therapy provides repetitive training, which may be beneficial for improving fine motor function. This study aims to evaluate the effect of app-based therapy compared to conventional hand therapy in improving dexterity in individuals with stroke.

Methodology

In total, 39 individuals within the first year of stroke with Brunnstrom stage of hand recovery IV to VI were randomly divided into three groups. All three groups received 60 min of therapy for 21 sessions over a period of 30 days. Group A received conventional hand therapy; Group B received app. therapy, while Group C received conventional therapy along with the app. therapy. All participants were assessed on the Nine-Hole Peg Test and Jebsen–Taylor Hand Function Test at the beginning and after completion of 21 sessions of intervention. Kruskal–Wallis (H) test and Wilcoxon test were used for statistical analysis.

Results

All three groups improved on hand function post-treatment. However, Group C demonstrated significant improvement with 16%–58% increase in hand function performance on outcome measures (p < 0.05).

Findings

Findings of the present study demonstrate improvement in dexterity with the app. therapy and combination therapy, in comparison to conventional therapy alone in individuals with stroke.

Originality

This experimental study focuses the first time on a structured protocol using an enabling technology adjunct to conventional physical therapy to improve hand function in individuals with stroke, which opens up the further scope in Neurorehabilitation.

Peer review

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2020-0144/

Feedback-guided exercises performed on a tablet touchscreen improve return to work, function, strength and healthcare usage more than an exercise program prescribed on paper for people with wrist, hand or finger injuries: a randomised trial

QUESTION

In people with bone and soft tissue injuries of the wrist, hand and/or fingers, do feedback-guided exercises performed on a tablet touchscreen hasten return to work, reduce healthcare usage and improve clinical recovery more than a home exercise program prescribed on paper?

DESIGN

Randomised, parallel-group trial with concealed allocation, assessor blinding and intention-to-treat analysis.

PARTICIPANTS

Seventy-four workers with limited functional ability due to bone and soft tissue injuries of the wrist, hand and/or fingers.

INTERVENTION

Participants in the experimental and control groups received the same in-patient physiotherapy and occupational therapy. Participants in the experimental group received a home exercise program using the ReHand tablet application, which guides exercises performed on a tablet touchscreen with feedback, monitoring and progression. Participants in the control group were prescribed an evidence-based home exercise program on paper.

OUTCOME MEASURES

The primary outcome was the time taken to return to work. Secondary outcomes included: healthcare usage (number of clinical appointments); and functional ability, pain intensity, and grip and pinch strength 2 and 4 weeks after randomisation.

RESULTS

Compared with the control group, the experimental group: returned to work sooner (MD -18 days, 95% CI -33 to -3); required fewer physiotherapy sessions (MD -7.4, 95% CI -13.1 to -1.6), rehabilitation consultations (MD -1.9, 95% CI -3.6 to 0.3) and plastic surgery consultations (MD -3.6, 95% CI -6.3 to -0.9); and had better short-term recovery of functional ability and pinch strength.

CONCLUSION

In people with bone and soft-tissue injuries of the wrist, hand and/or fingers, prescribing a feedback-guided home exercise program using a tablet-based application instead of a conventional program on paper hastened return to work and improved the short-term recovery of functional ability and pinch strength, while reducing the number of required healthcare appointments.

TRIAL REGISTRATION

ACTRN12619000344190.

Transcranial Alternating Current Stimulation of the Primary Motor Cortex after Skill Acquisition Improves Motor Memory Retention in Humans: A Double-Blinded Sham-Controlled Study

Consolidation leading to retention of motor memory following motor practice involves activity-dependent plastic processes in the corticospinal system. To investigate whether beta-band transcranial alternating current stimulation (tACS) applied immediately following skill acquisition can enhance ongoing consolidation processes and thereby motor skill retention 20 adults participated in a randomized, double-blinded, sham-controlled study. Participants received tACS at peak beta-band corticomuscular coherence (CMC) frequency or sham tACS for 10 min following practice of a visuomotor ankle dorsiflexion task. Performance was measured as the average percentage time on target. Electroencephalograhy (EMG) was measured at Cz and EMG from the right tibialis anterior muscle. CMC and intramuscular coherence (IMC) were estimated during 2-min tonic dorsiflexion. Motor skill retention was tested 1 and 7 days after motor practice. From the end of motor practice to the retention tests, motor performance improved more in the tACS group compared with the sham tACS group after 1 (P = 0.05) and 7 days (P < 0.001). At both retention tests, beta-band IMC increased in the tACS group compared with post-tACS. Beta-band CMC increased in the tACS group at retention day 1 compared with post-tACS. Changes in CMC but not IMC were correlated with performance 1 and 7 days following practice. This study shows that tACS applied at beta-band CMC frequency improves consolidation following visuomotor practice and increases beta-band CMC and IMC. We propose that oscillatory beta activity in the corticospinal system may facilitate consolidation of the motor skill.

Successful performance of basic gestures in tablet technology in post stroke patients: A feasibility study

BACKGROUND

Tablet technology is a promising tool for assisting therapeutic strategies in stroke rehabilitation. However, it is not clear whether the basic gestures (e.g. click, double-click) are feasible.

OBJECTIVE

This study aimed to assess the successful performance of gestures and associated factors.

METHODS

This cross-sectional study was conducted at a rehabilitation center in Austria. The successful tablet use was checked on a Samsung Galaxy Tab 4 (10.1 Wi-Fi 25.6 cm; 10.1 Zoll) with a specifically developed app. To identify factors associated with successful use, impairments in activities of daily living (Barthel index), cognitive functions (Montreal Cognitive Assessment, MoCA), motor functions (Nine-Hole Peg Test), and grip strength (handgrip dynamometer) were assessed.

RESULTS

One hundred and twenty-nine participants were analyzed, whereof 53.5% had a paretic upper limp and 69.2% were able to perform all gestures with at least one hand. Factors associated with successful use were higher Barthel index (OR: 1.06; 95% CI = 1.01-1.11) and MoCA (OR: 1.21; 95% CI = 1.01-1.44), whereas lower age (OR: 0.91; 95% CI = 0.83-0.99) and a paretic hand (OR: 0.12; 95% CI = 0.01-0.99) were associated with a lesser likelihood. Additionally, 18.6% successfully performed all gestures with the paretic hand, whereof 74% could not perform the double-click and 77.0% were not able to zoom.

CONCLUSIONS

The majority of stroke patients are able to perform the basic gestures on a tablet with at least one hand, but only few patients with paresis could do them. Gestures like double-clicking and zooming should be avoided when designing apps for rehabilitation, as especially these were found difficult.

The human sensorimotor cortex fosters muscle synergies through cortico-synergy coherence

In neuromotor control, the dimensionality of complex muscular activation patterns is effectively reduced through the emergence of muscle synergies. Muscle synergies are tailored to task-specific biomechanical needs. Traditionally, they are considered as low-dimensional neural output of the spinal cord and as such their coherent cortico-muscular pathways have remained underexplored in humans. We investigated whether muscle synergies have a higher-order origin, especially, whether they are manifest in the cortical motor network. We focused on cortical muscle synergy representations involved in balance control and examined changes in cortico-synergy coherence accompanying short-term balance training. We acquired electromyography and electro-encephalography and reconstructed cortical source activity using adaptive spatial filters. The latter were based on three muscle synergies decomposed from the activity of nine unilateral leg muscles using non-negative matrix factorization. The corresponding cortico-synergy coherence displayed phase-locked activity at the Piper rhythm, i.e., cortico-spinal synchronization around 40 Hz. Our study revealed the presence of muscle synergies in the motor cortex, in particular, in the paracentral lobule, known for the representation of lower extremities. We conclude that neural oscillations synchronize between the motor cortex and spinal motor neuron pools signifying muscle synergies. The corresponding cortico-synergy coherence around the Piper rhythm decreases with training-induced balance improvement.

Exercises using a touchscreen tablet application improved functional ability more than an exercise program prescribed on paper in people after surgical carpal tunnel release: a randomised trial

QUESTION

In people who have undergone surgical carpal tunnel release, do sensorimotor-based exercises performed on the touchscreen of a tablet device improve outcomes more than a conventional home exercise program prescribed on paper?

DESIGN

Randomised, parallel-group trial with concealed allocation, assessor blinding, and intention-to-treat analysis.

PARTICIPANTS

Fifty participants within 10 days of surgical carpal tunnel release.

INTERVENTION

Each participant was prescribed a 4-week home exercise program. Participants in the experimental group received the ReHand tablet application, which administered and monitored exercises via the touchscreen. The control group was prescribed a home exercise program on paper, as is usual practice in the public hospital system.

OUTCOME MEASURES

The primary outcome was functional ability of the hand, reported using the shortened form of the Disabilities of the Arm, Shoulder and Hand (QuickDASH) questionnaire. Secondary outcomes were grip strength, pain intensity measured on a 10-cm visual analogue scale, and dexterity measured with the Nine-Hole Peg Test. Outcomes were measured by a blinded assessor at baseline and at the end of the 4-week intervention period.

RESULTS

At Week 4, functional ability improved significantly more in the experimental group than the control group (MD -21, 95% CI -33 to -9) on the QuickDASH score (0 to 100). Although the mean estimates of effect on the secondary outcome also all favoured the experimental group, none reached statistical significance: grip strength (MD 5.6 kg, 95% CI -0.5 to 11.7), pain (MD -1.4 cm, 95% CI -2.9 to 0.1), and dexterity (MD -1.3 seconds, 95% CI -3.7 to 1.1).

CONCLUSION

Use of the ReHand tablet application for early rehabilitation after carpal tunnel release is more effective in the recovery of functional ability than a conventional home exercise program. It remains unclear whether there are any benefits in grip strength, pain or dexterity.

TRIAL REGISTRATION

ACTRN12618001887268.

Improving Precision Force Control With Low-Frequency Error Amplification Feedback: Behavioral and Neurophysiological Mechanisms

Although error amplification (EA) feedback has been shown to improve performance on visuomotor tasks, the challenge of EA is that it concurrently magnifies task-irrelevant information that may impair visuomotor control. The purpose of this study was to improve the force control in a static task by preclusion of high-oscillatory components in EA feedback that cannot be timely used for error correction by the visuomotor system. Along with motor unit behaviors and corticomuscular coherence, force fluctuations (Fc) were modeled with non-linear SDA to contrast the reliance of the feedback process and underlying neurophysiological mechanisms by using real feedback, EA, and low-frequency error amplification (LF-EA). During the static force task in the experiment, the EA feedback virtually potentiated the size of visual error, whereas the LF-EA did not channel high-frequency errors above 0.8 Hz into the amplification process. The results showed that task accuracy was greater with the LF-EA than with the real and EA feedback modes, and that LF-EA led to smaller and more complex Fc. LF-EA generally led to smaller SDA variables of Fc (critical time points, critical point of Fc, the short-term effective diffusion coefficient, and short-term exponent scaling) than did real feedback and EA. The use of LF-EA feedback increased the irregularity of the ISIs of MUs but decreased the RMS of the mean discharge rate, estimated with pooled MU spike trains. Beta-range EEG–EMG coherence spectra (13–35 Hz) in the LF-EA condition were the greatest among the three feedback conditions. In summary, amplification of low-frequency errors improves force control by shifting the relative significances of the feedforward and feedback processes. The functional benefit arises from the increase in the common descending drive to promote a stable state of MU discharges.

Dynamical Coordination of Hand Intrinsic Muscles for Precision Grip in Diabetes Mellitus

This study investigated the effects of diabetes mellitus (DM) on dynamical coordination of hand intrinsic muscles during precision grip. Precision grip was tested using a custom designed apparatus with stable and unstable loads, during which the surface electromyographic (sEMG) signals of the abductor pollicis brevis (APB) and first dorsal interosseous (FDI) were recorded simultaneously. Recurrence quantification analysis (RQA) was applied to quantify the dynamical structure of sEMG signals of the APB and FDI; and cross recurrence quantification analysis (CRQA) was used to assess the intermuscular coupling between the two intrinsic muscles. This study revealed that the DM altered the dynamical structure of muscle activation for the FDI and the dynamical intermuscular coordination between the APB and FDI during precision grip. A reinforced feedforward mechanism that compensates the loss of sensory feedbacks in DM may be responsible for the stronger intermuscular coupling between the APB and FDI muscles. Sensory deficits in DM remarkably decreased the capacity of online motor adjustment based on sensory feedback, rendering a lower adaptability to the uncertainty of environment. This study shed light on inherent dynamical properties underlying the intrinsic muscle activation and intermuscular coordination for precision grip and the effects of DM on hand sensorimotor function.

Progressive practice promotes motor learning and repeated transient increases in corticospinal excitability across multiple days

BACKGROUND

A session of motor skill learning is accompanied by transient increases in corticospinal excitability(CSE), which are thought to reflect acute changes in neuronal connectivity associated with improvements in sensorimotor performance. Factors influencing changes in excitability and motor skill with continued practice remain however to be elucidated.

OBJECTIVE/HYPOTHESIS

Here we investigate the hypothesis that progressive motor practice during consecutive days can induce repeated transient increases in corticospinal excitability and promote motor skill learning.

METHODS

Changes in motor performance and CSE were assessed during 4 consecutive days of skill learning and 8 days after the last practice session. CSE was assessed as area under recruitment curves(RC) using transcranial magnetic stimulation(TMS). Two groups of participants(n = 12) practiced a visuomotor tracking-task with task difficulty progressively increased with individual proficiency(PPG) or with the same task level throughout all 4 days(NPPG).

RESULTS

Progressive practice resulted in superior motor learning compared to NPPG(p < 0.001). Whereas NPPG displayed increased CSE following only the first day of practice(p < 0.001), progressive motor practice was accompanied by increases in CSE on both the first and the final session of motor practice(p = 0.006). Eight days after ended practice, the groups showed similar CSE, but PPG maintained superior performance at a skilled task level and transfer task performance(p < 0.005,p = 0.029).

CONCLUSION

The results demonstrate that progressive practice promotes both motor learning and repeated increases in CSE across multiple days. While changes in CSE did not relate to learning our results suggest that they signify successful training. Progressive practice is thus important for optimizing neurorehabilitation and motor practice protocols in general.

Corticomuscular coherence in the acute and subacute phase after stroke

OBJECTIVE

Stroke is one of the leading causes of physical disability due to damage of the motor cortex or the corticospinal tract. In the present study we set out to investigate the role of adaptations in the corticospinal pathway for motor recovery during the subacute phase after stroke.

METHODS

We examined 19 patients with clinically diagnosed stroke and 18 controls. The patients had unilateral mild to moderate weakness of the hand. Each patient attended two sessions at approximately 3days (acute) and 38days post stroke (subacute). Task-related changes in the communication between motor cortex and muscles were evaluated from coupling in the frequency domain between EEG and EMG during movement of the paretic hand.

RESULTS

Corticomuscular coherence (CMC) and intermuscular coherence (IMC) were reduced in patients as compared to controls. Paretic hand motor performance improved within 4-6weeks after stroke, but no change was observed in CMC or IMC.

CONCLUSIONS

CMC and IMC were reduced in patients in the early phase after stroke. However, changes in coherence do not appear to be an efficient marker for early recovery of hand function following stroke.

SIGNIFICANCE

This is the first study to demonstrate sustained reduced coherence in acute and subacute stroke.

How plastic are human spinal cord motor circuitries?

Human and animal studies have documented that neural circuitries in the spinal cord show adaptive changes caused by altered supraspinal and/or afferent input to the spinal circuitry in relation to learning, immobilization, injury and neurorehabilitation. Reversible adaptations following, e.g. the acquisition or refinement of a motor skill rely heavily on the functional integration between supraspinal and sensory inputs to the spinal cord networks. Accordingly, what is frequently conceived as a change in the spinal circuitry may be a change in either descending or afferent input or in the relative integration of these, i.e. a change in the neuronal weighting. This is evident from findings documenting only task-specific functional changes after periods of altered inputs whereas resting responses remain unaffected. In fact, the proximity of the spinal circuitry to the outer world may demand a more rigid organization compared to the highly flexible cortical circuits. The understanding of all of this is important for the planning and execution of neurorehabilitation.

To be active through indoor-climbing: an exploratory feasibility study in a group of children with cerebral palsy and typically developing children

BACKGROUND

Cerebral Palsy (CP) is the most common cause of motor disabilities in children and young adults and it is also often associated with cognitive and physiological challenges. Climbing requires a multifaceted repertoire of movements, participants at all levels of expertise may be challenged functionally and cognitively, making climbing of great potential interest in (re)habilitation settings. However, until now only few research projects have investigated the feasibility of climbing as a potential activity for heightening physical activity in children with CP and the possible beneficial effects of climbing activities in populations with functional and/or cognitive challenges. The aim of this study was therefore to test the feasibility of an intensive 3 weeks indoor-climbing training program in children with CP and typically developing (TD) peers. In addition we evaluated possible functional and cognitive benefits of 3 weeks of intensive climbing training in 11 children with cerebral palsy (CP) aged 11-13 years and six of their TD peers.

METHOD

The study was designed as a feasibility and interventional study. We evaluated the amount of time spent being physically active during the 9 indoor-climbing training sessions, and climbing abilities were measured. The participants were tested in a series of physiological, psychological and cognitive tests: two times prior to and one time following the training in order to explore possible effects of the intervention.

RESULTS

The children accomplished the training goal of a total of nine sessions within the 3-week training period. The time of physical activity during a 2:30 h climbing session, was comparably high in the group of children with CP and the TD children. The children with CP were physically active on average for almost 16 h in total during the 3 weeks. Both groups of participants improved their climbing abilities, the children with CP managed to climb a larger proportion of the tested climbing route at the end of training and the TD group climbed faster. For the children with CP this was accompanied by significant improvements in the Sit-to-stand test (p < 0.01), increased rate of force development in the least affected hand during an explosive pinch test and increased muscular-muscular coherence during a pinch precision test (p < 0.05). We found no improvements in maximal hand or finger strength and no changes in cognitive abilities or psychological well-being in any of the groups.

CONCLUSIONS

These findings show that it is possible to use climbing as means to make children with CP physically active. The improved motor abilities obtained through the training is likely reflected by increased synchronization between cortex and muscles, which results in a more efficient motor unit recruitment that may be transferred to daily functional abilities.

TRIAL REGISTRATION

ISRCTN18006574; day of registration: 09/05/2017; the trial is registered retrospectively.

A Pilot Study on the Effects of Transcranial Direct Current Stimulation on Brain Rhythms and Entropy during Self-Paced Finger Movement using the Epoc Helmet

Transcranial direct current stimulation (tDCS) of the cerebellum is emerging as a novel non-invasive tool to modulate the activity of the cerebellar circuitry. In a single blinded study, we applied anodal tDCS (atDCS) of the cerebellum to assess its effects on brain entropy and brain rhythms during self-paced sequential finger movements in a group of healthy volunteers. Although wearable electroencephalogram (EEG) systems cannot compete with traditional clinical/laboratory set-ups in terms of accuracy and channel density, they have now reached a sufficient maturity to envision daily life applications. Therefore, the EEG was recorded with a comfortable and easy to wear 14 channels wireless helmet (Epoc headset; electrode location was based on the 10-20 system). Cerebellar neurostimulation modified brain rhythmicity with a decrease in the delta band (electrode F3 and T8, p < 0.05). By contrast, our study did not show any significant change in entropy ratios and laterality coefficients (LC) after atDCS of the cerebellum in the 14 channels. The cerebellum is heavily connected with the cerebral cortex including the frontal lobes and parietal lobes via the cerebello-thalamo-cortical pathway. We propose that the effects of anodal stimulation of the cerebellar cortex upon cerebral cortical rhythms are mediated by this key-pathway. Additional studies using high-density EEG recordings and behavioral correlates are now required to confirm our findings, especially given the limited coverage of Epoc headset.

Changes in corticospinal drive to spinal motoneurones following tablet-based practice of manual dexterity

The use of touch screens, which require a high level of manual dexterity, has exploded since the development of smartphone and tablet technology. Manual dexterity relies on effective corticospinal control of finger muscles, and we therefore hypothesized that corticospinal drive to finger muscles can be optimized by tablet‐based motor practice. To investigate this, sixteen able‐bodied females practiced a tablet‐based game (3 × 10 min) with their nondominant hand requiring incrementally fast and precise pinching movements involving the thumb and index fingers. The study was designed as a semirandomized crossover study where the participants attended one practice‐ and one control session. Before and after each session electrophysiological recordings were obtained during three blocks of 50 precision pinch movements in a standardized setup resembling the practiced task. Data recorded during movements included electroencephalographic (EEG) activity from primary motor cortex and electromyographic (EMG) activity from first dorsal interosseous (FDI) and abductor pollicis brevis (APB) muscles. Changes in the corticospinal drive were evaluated from coupling in the frequency domain (coherence) between EEG–EMG and EMG–EMG activity. Following motor practice performance improved significantly and a significant increase in EEG‐EMG_APB and EMG_APB‐EMG_FDI coherence in the beta band (15–30 Hz) was observed. No changes were observed after the control session. Our results show that tablet‐based motor practice is associated with changes in the common corticospinal drive to spinal motoneurons involved in manual dexterity. Tablet‐based motor practice may be a motivating training tool for stroke patients who struggle with loss of dexterity.

Influence of dual-task on postexercise facilitation: a transcranial magnetic stimulation study

In this study we investigated the effect of a dual task (DT) comprised of a nonfatiguing leg and foot extension coupled with a calculation task on postexercise facilitation (PEF) of motor evoked potentials (MEPs) tested by using transcranial magnetic stimulation (TMS). Twelve right-handed healthy subjects participated in the study. They were required to perform a motor task, a cognitive task and a DT. The motor task consisted of extending the right leg and foot for 30 sec at 20% of the maximal voluntary contraction. The cognitive task consisted of a 30-sec backward calculation. In the DT condition, motor and cognitive tasks were performed concurrently. Resting motor threshold and 10 MEPs were collected before and immediately after each task. TMS was delivered to the motor hot spot of the right vastus lateralis and tibialis anterior (TA) muscles. Results showed that exercise induced a significant PEF in both VL and TA muscles while calculation was not associated with significant PEF. Furthermore, DT was associated with lack of significant PEF in both muscles (VL, 116.1%±9.6%; TA, 115.7%±9%). Our data indicates DT interference on corticospinal excitability after a nonfatiguing exercise. Our experimental paradigm may be used to address postexercise motor cortex plastic adaptations induced by motor and cognitive tasks of different complexity in sport, aging and neuropsychiatric diseases.