A hybrid brain-muscle-machine interface for stroke rehabilitation: Usability and functionality validation in a 2-week intensive intervention.

Introduction: The primary constraint of non-invasive brain-machine interfaces (BMIs) in stroke rehabilitation lies in the poor spatial resolution of motor intention related neural activity capture. To address this limitation, hybrid brain-muscle-machine interfaces (hBMIs) have been suggested as superior alternatives. These hybrid interfaces incorporate supplementary input data from muscle signals to enhance the accuracy, smoothness and dexterity of rehabilitation device control. Nevertheless, determining the distribution of control between the brain and muscles is a complex task, particularly when applied to exoskeletons with multiple degrees of freedom (DoFs). Here we present a feasibility, usability and functionality study of a bio-inspired hybrid brain-muscle machine interface to continuously control an upper limb exoskeleton with 7 DoFs. Methods: The system implements a hierarchical control strategy that follows the biologically natural motor command pathway from the brain to the muscles. Additionally, it employs an innovative mirror myoelectric decoder, offering patients a reference model to assist them in relearning healthy muscle activation patterns during training. Furthermore, the multi-DoF exoskeleton enables the practice of coordinated arm and hand movements, which may facilitate the early use of the affected arm in daily life activities. In this pilot trial six chronic and severely paralyzed patients controlled the multi-DoF exoskeleton using their brain and muscle activity. The intervention consisted of 2 weeks of hBMI training of functional tasks with the system followed by physiotherapy. Patients' feedback was collected during and after the trial by means of several feedback questionnaires. Assessment sessions comprised clinical scales and neurophysiological measurements, conducted prior to, immediately following the intervention, and at a 2-week follow-up. Results: Patients' feedback indicates a great adoption of the technology and their confidence in its rehabilitation potential. Half of the patients showed improvements in their arm function and 83% improved their hand function. Furthermore, we found improved patterns of muscle activation as well as increased motor evoked potentials after the intervention. Discussion: This underscores the significant potential of bio-inspired interfaces that engage the entire nervous system, spanning from the brain to the muscles, for the rehabilitation of stroke patients, even those who are severely paralyzed and in the chronic phase.

Testing spasticity mechanisms in chronic stroke before and after intervention with contralesional motor cortex 1 Hz rTMS and physiotherapy.

BACKGROUND: Previous studies showed that repetitive transcranial magnetic stimulation (rTMS) reduces spasticity after stroke. However, clinical assessments like the modified Ashworth scale, cannot discriminate stretch reflex-mediated stiffness (spasticity) from passive stiffness components of resistance to muscle stretch. The mechanisms through which rTMS might influence spasticity are also not understood. METHODS: We measured the effects of contralesional motor cortex 1 Hz rTMS (1200 pulses + 50 min physiotherapy: 3×/week, for 4-6 weeks) on spasticity of the wrist flexor muscles in 54 chronic stroke patients using a hand-held dynamometer for objective quantification of the stretch reflex response. In addition, we measured the excitability of three spinal mechanisms thought to be related to post-stroke spasticity: post-activation depression, presynaptic inhibition and reciprocal inhibition before and after the intervention. Effects on motor impairment and function were also assessed using standardized stroke-specific clinical scales. RESULTS: The stretch reflex-mediated torque in the wrist flexors was significantly reduced after the intervention, while no change was detected in the passive stiffness. Additionally, there was a significant improvement in the clinical tests of motor impairment and function. There were no significant changes in the excitability of any of the measured spinal mechanisms. CONCLUSIONS: We demonstrated that contralesional motor cortex 1 Hz rTMS and physiotherapy can reduce the stretch reflex-mediated component of resistance to muscle stretch without affecting passive stiffness in chronic stroke. The specific physiological mechanisms driving this spasticity reduction remain unresolved, as no changes were observed in the excitability of the investigated spinal mechanisms.

Challenges of neural interfaces for stroke motor rehabilitation.

More than 85% of stroke survivors suffer from different degrees of disability for the rest of their lives. They will require support that can vary from occasional to full time assistance. These conditions are also associated to an enormous economic impact for their families and health care systems. Current rehabilitation treatments have limited efficacy and their long-term effect is controversial. Here we review different challenges related to the design and development of neural interfaces for rehabilitative purposes. We analyze current bibliographic evidence of the effect of neuro-feedback in functional motor rehabilitation of stroke patients. We highlight the potential of these systems to reconnect brain and muscles. We also describe all aspects that should be taken into account to restore motor control. Our aim with this work is to help researchers designing interfaces that demonstrate and validate neuromodulation strategies to enforce a contingent and functional neural linkage between the central and the peripheral nervous system. We thus give clues to design systems that can improve or/and re-activate neuroplastic mechanisms and open a new recovery window for stroke patients.

Measuring resistance to externally induced movement of the wrist joint in chronic stroke patients using an objective hand-held dynamometer.

Objective: We evaluated the resistance to externally induced wrist extension in chronic stroke patients. We aimed to objectively measure and distinguish passive (muscle and soft tissue stiffness) and active (spasticity and spastic dystonia) components of the resistance. Methods: We used a hand-held dynamometer, which measures torque, joint movement and electromyography (EMG) simultaneously, to assess the resistance to externally induced wrist extension. Slow and fast stretches were applied to the affected and unaffected wrists in 57 chronic stroke patients (57 ±â€¯11 years). We extracted from the data parameters that represent passive and muscle activity components and assessed the validity, test-retest reliability and the clinical utility of the measurement. Results: The analysis showed (1) a significant difference in the passive and muscle activity components between the affected and unaffected sides; (2) a significant correlation between passive and muscle activity components and the modified Ashworth scale (MAS); (3) a significant difference between the subgroups of patients stratified by the MAS; (4) an excellent intra-rater reliability on each of the passive and muscle activity components with intra-class coefficients between 0.92 and 0.99; (5) and small measurement error. Conclusions: Using a hand-held dynamometer, we were able to objectively measure the resistance to muscle stretch in the wrist joint in chronic stroke patients and discriminate muscle overactivity components from muscle and soft tissue stiffness. We demonstrated validity, test-retest reliability and the clinical utility of the measurement. Significance: Quantification of the different components of resistance to externally induced movement enables the objective evaluation of neurorehabilitation effects in chronic stroke patients.

Declining fitness and physical education lessons in UK adolescents.

OBJECTIVES: The objective was to determine recent cross-sectional trends in health-related fitness (HRF) in secondary school students by studying the 13-14 years old age group repeatedly over 6 years, considering parallel national trends in physical education (PE). METHODS: Height, weight, broad jump, grip strength, 20 m shuttle run and throwing and catching skills were measured by the same research team using standardised techniques from 2014 to 2019. Trends in these HRF measures were assessed by linear regression, adjusting for school, sex and height. Interactions with fitness and body mass index (BMI) were tested. The number of PE lessons reported in the UK Annual School Workforce Census between 2010 and 2019 for all state-funded secondary schools was analysed. RESULTS: Grip strength (B=-0.60, 95% CI -0.78 to -0.41), broad jump (B=-1.16, 95% CI -1.99 to -0.34), 20 m shuttle run (B=-1.85, 95% CI -2.58 to -1.12) and throwing and catching skills (B=-0.12, 95% CI -0.15 to -0.08) declined significantly over the study period. There was a greater reduction in broad jump and grip strength in adolescents with low fitness and a greater reduction in fitness and motor competence in adolescents with normal BMI. These declines coincided with a 16% reduction nationally in secondary school PE between 2010 (333 800 hours) and 2019 (280 725 hours). CONCLUSION: Adolescent HRF has declined in recent years, in parallel with PE lessons. Declines were observed across all young people and particularly those of low fitness and normal BMI. To reach the majority of young people, policy makers could increase PE in schools to increase activity and prevent worsening fitness and health in future generations.

Psychophysiological treatment of chronic tinnitus: A review.

Subjective chronic tinnitus consists of a more or less continuous perception of sound in the absence of a corresponding acoustic source, which can lead to various psychological problems like depression, anxiety, attentional deficits and sleep disturbances. The prevalence is 10%-15% of the general population. Various therapy and management options have been proposed, but outcomes vary, and no generally accepted cure exists. In this review, the coherence of the most frequently used aetiological models shall be evaluated, and the efficacy of several treatment options will be discussed. With respect to tinnitus treatments, we focus on controlled studies and meta-analyses. Although there are some therapies that outweigh placebo effects such as cognitive behavioural therapy, neurofeedback or neuromodulation techniques, they mainly target secondary symptoms and not the tinnitus tone itself. Furthermore, positive treatment effects only seem to last for a limited period of time. We conclude that long-lasting combination therapies such as neurofeedback of auditory cortex inhibitory EEG signatures, cognitive therapy and sound-tactile stimulation may provide more efficient outcomes if they target the intensity of the tinnitus tone itself and not only secondary psychological symptoms.

A School-Based Screening Tool for Adolescents With Low Motor Coordination Abilities.

This study sought to select the most relevant test items from the Bruininks-Oseretsky Test of Motor Proficiency, Second Edition (BOTMP-2) and from a selection of health-related fitness tests for identifying school teenagers with poor motor coordination. The 241 participants in this study (144 boys, 97 girls aged 13-14 years old) were tested on the short form of the BOTMP-2 and on the following additional fitness tests: (a) seated medicine ball test, (b) broad jump, (c) handgrip strength, (d) alternate hand ball wall toss, (e) 10 × 5-meter agility shuttle run, and (f) Chester step test. We performed a factor analysis of participant scores on these various tasks and BOTMP-2 test items to reduce them to the least number of meaningful and useful items. Four factors explained 45% of the data variance: gross motor skills and power (including broad jump, hand ball toss, shuttle run, and sit-ups tests); fine motor skills (including copying star, following the maze and paper folding); core strength and balance (including push-ups, hopping, and balance beam); and general body strength (including medicine ball throw and handgrip). We conclude that an efficient school-based battery of test items to screen 13-14 year old adolescents for fitness and coordination should assess these four factors and might especially rely upon the broad jump, copying a star shape, hopping handgrip strength, aerobic fitness, and wall ball toss.

The relationship of gross upper and lower limb motor competence to measures of health and fitness in adolescents aged 13-14 years.

INTRODUCTION: Motor competence (MC) is an important factor in the development of health and fitness in adolescence. AIMS: This cross-sectional study aims to explore the distribution of MC across school students aged 13-14 years old and the extent of the relationship of MC to measures of health and fitness across genders. METHODS: A total of 718 participants were tested from three different schools in the UK, 311 girls and 407 boys (aged 13-14 years), pairwise deletion for correlation variables reduced this to 555 (245 girls, 310 boys). Assessments consisted of body mass index, aerobic capacity, anaerobic power, and upper limb and lower limb MC. The distribution of MC and the strength of the relationships between MC and health/fitness measures were explored. RESULTS: Girls performed lower for MC and health/fitness measures compared with boys. Both measures of MC showed a normal distribution and a significant linear relationship of MC to all health and fitness measures for boys, girls and combined genders. A stronger relationship was reported for upper limb MC and aerobic capacity when compared with lower limb MC and aerobic capacity in boys (t=-2.21, degrees of freedom=307, P=0.03, 95% CI -0.253 to -0.011). CONCLUSION: Normally distributed measures of upper and lower limb MC are linearly related to health and fitness measures in adolescents in a UK sample. TRIAL REGISTRATION NUMBER: NCT02517333.

Neural Substrates of Cognitive Motor Interference During Walking; Peripheral and Central Mechanisms.

Current gait control models suggest that independent locomotion depends on central and peripheral mechanisms. However, less information is available on the integration of these mechanisms for adaptive walking. In this cross-sectional study, we investigated gait control mechanisms in people with Parkinson's disease (PD) and healthy older (HO) adults: at self-selected walking speed (SSWS) and at fast walking speed (FWS). We measured effect of additional cognitive task (DT) and increased speed on prefrontal (PFC) and motor cortex (M1) activation, and Soleus H-reflex gain. Under DT-conditions we observed increased activation in PFC and M1. Whilst H-reflex gain decreased with additional cognitive load for both groups and speeds, H-reflex gain was lower in PD compared to HO while walking under ST condition at SSWS. Attentional load in PFC excites M1, which in turn increases inhibition on H-reflex activity during walking and reduces activity and sensitivity of peripheral reflex during the stance phase of gait. Importantly this effect on sensitivity was greater in HO. We have previously observed that the PFC copes with increased attentional load in young adults with no impact on peripheral reflexes and we suggest that gait instability in PD may in part be due to altered sensorimotor functioning reducing the sensitivity of peripheral reflexes.

A long-term self-managed handwriting intervention for people with Parkinson's disease: results from the control group of a phase II randomized controlled trial.

OBJECTIVE: To report on the control group of a trial primarily designed to investigate exercise for improving mobility in people with Parkinson's disease (pwP). The control group undertook a handwriting intervention to control for attention and time spent practising a specific activity. DESIGN: Secondary analysis of a two-arm parallel phase II randomized controlled trial with blind assessment. SETTING: Community. PARTICIPANTS: PwP able to walk ⩾100 m and with no contraindication to exercise were recruited from the Thames Valley, UK, and randomized (1:1) to exercise or handwriting, via a concealed computer-generated list. INTERVENTION: Handwriting was undertaken at home and exercise in community facilities; both were delivered through workbooks with monthly support visits and involved practice for 1 hour, twice weekly, over a period of six months. MAIN MEASURES: Handwriting was assessed, at baseline, 3, 6 and 12 months, using a pangram giving writing speed, amplitude (area) and progressive reduction in amplitude (ratio). The Movement Disorder Society (MDS)-Unified Parkinson's Disease Rating Scale (UPDRS) item 2.7 measured self-reported handwriting deficits. RESULTS: In all, 105 pwP were recruited (analysed: n = 51 handwriting, n = 54 exercise). A total of 40 pwP adhered to the handwriting programme, most completing ⩾1 session/week. Moderate effects were found for amplitude (total area: d = 0.32; 95% confidence interval (CI): -0.11 to 0.7; P = 0.13) in favour of handwriting over a period of12 months; effects for writing speed and ratio parameters were small ≤0.11. Self-reported handwriting difficulties also favoured handwriting (UPDRS 2.7: odds ratio (OR) = 0.55; 95% CI: 0.34 to 0.91; P = 0.02). No adverse effects were reported. CONCLUSION: PwP generally adhere to self-directed home handwriting which may provide benefit with minimal risk. Encouraging effects were found in writing amplitude and, moreover, perceived ability.