Nada Signal

Reliability of lower limb motor evoked potentials in stroke and healthy populations: How many responses are needed?

OBJECTIVE To determine the intra- and inter-session reliability of motor evoked potential (MEP) size parameters in the lower limb of patients with stroke, focussing on the number of MEPs collected and the method of measuring MEP size. METHODS Transcranial magnetic stimulation was used to elicit MEPs in the soleus muscle of patients with stroke (n=13) and age-matched healthy participants (n=13) during low level muscle activation. Two sets of 10 responses were collected in the first session and a further 10 responses collected in a second session held 7 days later. Four MEP size measurements were made using 4, 6, 8, or all 10 of the MEPs collected. Intra- and inter-session reliability was examined using intraclass correlation coefficients (ICC) and typical percentage error. RESULTS Intrasession ICC statistics using 6 or more MEPs were >0.85 in the stroke group but intersession values were all <0.5. Reliability was best when measuring parameters from individual MEPs rather than averaged responses. CONCLUSIONS Reliability of intrasession MEP size is excellent in the lower limb of patients with stroke using as few as 6 MEPs but intersession reliability is poor. SIGNIFICANCE Comparing MEP size measures across two or more sessions is questionable in the lower limb of patients with stroke.

Induction of Long-term Depression-like Plasticity by Pairings of Motor Imagination and Peripheral Electrical Stimulation

Long-term depression (LTD) and long-term potentiation (LTP)-like plasticity are models of synaptic plasticity which have been associated with memory and learning. The induction of LTD and LTP-like plasticity, using different stimulation protocols, has been proposed as a means of addressing abnormalities in cortical excitability associated with conditions such as focal hand dystonia and stroke. The aim of this study was to investigate whether the excitability of the cortical projections to the tibialis anterior (TA) muscle could be decreased when dorsiflexion of the ankle joint was imagined and paired with peripheral electrical stimulation (ES) of the nerve supplying the antagonist soleus muscle. The effect of stimulus timing was evaluated by comparing paired stimulation timed to reach the cortex before, at and after the onset of imagined movement. Fourteen healthy subjects participated in six experimental sessions held on non-consecutive days. The timing of stimulation delivery was determined offline based on the contingent negative variation (CNV) of electroencephalography brain data obtained during imagined dorsiflexion. Afferent stimulation was provided via a single pulse ES to the peripheral nerve paired, based on the CNV, with motor imagination of ankle dorsiflexion. A significant decrease (P = 0.001) in the excitability of the cortical projection of TA was observed when the afferent volley from the ES of the tibial nerve (TN) reached the cortex at the onset of motor imagination based on the CNV. When TN stimulation was delivered before (P = 0.62), or after (P = 0.23) imagined movement onset there was no significant effect. Nor was a significant effect found when ES of the TN was applied independent of imagined movement (P = 0.45). Therefore, the excitability of the cortical projection to a muscle can be inhibited when ES of the nerve supplying the antagonist muscle is precisely paired with the onset of imagined movement.

Pairing Voluntary Movement and Muscle-Located Electrical Stimulation Increases Cortical Excitability

Learning new motor skills has been correlated with increased cortical excitability. In this study, different location of electrical stimulation (ES), nerve, or muscle, was paired with voluntary movement to investigate if ES paired with voluntary movement (a) would increase the excitability of cortical projections to tibialis anterior and (b) if stimulation location mattered. Cortical excitability changes were quantified using motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) at varying intensities during four conditions. Twelve healthy subjects performed 50 dorsiflexions at the ankle during nerve or muscle ES at motor threshold (MTh). ES alone was delivered 50 times and the movement was performed 50 times. A significant increase in the excitability from pre- to post-intervention (P = 0.0061) and pre- to 30 min post-intervention (P = 0.017) measurements was observed when voluntary movement was paired with muscle ES located at tibialis anterior. An increase of 50 ± 57 and 28 ± 54% in the maximum MEPs was obtained for voluntary movement paired with muscle-located and nerve-located ES, respectively. The maximum MEPs for voluntary movement alone and muscle-located ES alone were −5 ± 28 and 2 ± 42%, respectively. Pairing voluntary movement with muscle-located ES increases excitability of corticospinal projections of tibialis anterior in healthy participants. This finding suggests that active participation during muscle-located ES protocols increases cortical excitability to a greater extent than stimulation alone. The next stage of this research is to investigate the effect in people with stroke. The results may have implications for motor recovery in patients with motor impairments following neurological injury.

Central and peripheral contributions to neuromuscular fatigue in people with stroke

Abstract Objective: To evaluate the evidence for neuromuscular fatigue following stroke and to consider the implications of the findings for clinical practice and future research. Methods: A search of Ebsco Health and Ovid electronic search engines was undertaken using key search terms. In addition, the reference lists of pertinent articles were screened for other relevant articles. Results: A total of five relevant research papers were identified for review. Discussion: There is physiological evidence to suggest that changes in the development of neuromuscular fatigue are likely to occur in both the nervous system (central neuromuscular fatigue) and muscle (peripheral neuromuscular fatigue) following stroke. Based on the experimental research available it may be asserted that people with stroke fatigue differently from control participants, however, the source of these differences remains unclear. There are indications of a relative reduction in the amount of peripheral neuromuscular fatigue, and an increase in the amount of central neuromuscular fatigue, experienced by people following stroke. However, the validity of protocols for measuring fatigue in pathological populations can be questioned. Further elucidation of the presence, extent and cause of neuromuscular fatigue through experimental research, and consideration of neuromuscular fatigue during the rehabilitation process, is warranted.

Paired associative stimulation delivered by pairing movement-related cortical potentials with peripheral electrical stimulation: An investigation of the duration of neuromodulatory effects

Novel paired associative stimulation (novel‐PAS), delivered by pairing movement‐related cortical potentials (MRCPs) with electrical stimulation of somatosensory afferents, is an innovative neuromodulatory intervention. Novel‐PAS results in increased corticomotor excitability and has potential as a rehabilitative adjunct to improve outcomes following stroke. The duration of its excitatory effect has important implications for how this novel PAS intervention might be applied within a traditional therapy session, but previous research has not explored its effects beyond 30 min post‐intervention.

Quantification of Movement-Related EEG Correlates Associated with Motor Training: A Study on Movement-Related Cortical Potentials and Sensorimotor Rhythms

The ability to learn motor tasks is important in both healthy and pathological conditions. Measurement tools commonly used to quantify the neurophysiological changes associated with motor training such as transcranial magnetic stimulation and functional magnetic resonance imaging pose some challenges, including safety concerns, utility, and cost. EEG offers an attractive alternative as a quantification tool. Different EEG phenomena, movement-related cortical potentials (MRCPs) and sensorimotor rhythms (event-related desynchronization—ERD, and event-related synchronization—ERS), have been shown to change with motor training, but conflicting results have been reported. The aim of this study was to investigate how the EEG correlates (MRCP and ERD/ERS) from the motor cortex are modulated by short (single session in 14 subjects) and long (six sessions in 18 subjects) motor training. Ninety palmar grasps were performed before and after 1 × 45 (or 6 × 45) min of motor training with the non-dominant hand (laparoscopic surgery simulation). Four channels of EEG were recorded continuously during the experiments. The MRCP and ERD/ERS from the alpha/mu and beta bands were calculated and compared before and after the training. An increase in the MRCP amplitude was observed after a single session of training, and a decrease was observed after six sessions. For the ERD/ERS analysis, a significant change was observed only after the single training session in the beta ERD. In conclusion, the MRCP and ERD change as a result of motor training, but they are subject to a marked intra- and inter-subject variability.

footPress: An Open-Source MATLAB Toolbox for Analysis of Pedobarography Data

Pedobarographic data is valuable in understanding locomotor function in both research and clinical settings. However, commercially available software do not enable easy customisation of data processing and presentation. We have developed a toolbox for processing plantar pressure data using the cross-platform MATLAB programming language. The main features of the toolbox include data visualisation, sensor masking, time series, center of pressure and multi-segment analysis along with report generation. The toolbox can be used with an intuitive graphical user interface (GUI) without working with the underlying code. However, a functional approach to code implementation ensures that the toolbox can be used as a set of independent functions and new functions can easily be added. The code of the toolbox is open-source under the MIT License and available online at https://github.com/GallVp/footPress.

A tangible interface and augmented reality game for facilitating sit-to-stand exercises for stroke rehabilitation

This paper reports on how the design of an augmented reality (AR) exergame can facilitate engagement in independent stroke rehabilitation. Our system converted prescribed exercises (sit-to-stand) into engaging active gameplay using AR mobile technology and a proprietary designed tangible interface. Neurophysiotherapists and stroke patients tested the games usability and the engagement strategies. We suggest that exergames facilitated by the Internet of Things (IoT) can help facilitate engagement in stroke rehabilitation therapies by incorporating meaningful play, progression and be designed under a stroke-patient friendly approach. In particular, AR can increase meaningful play by incorporating the patients home environment, health benefit beliefs and personal preferences into the virtual gameplay. AR can facilitate and track progression as the patient recovers and improves in the game. Designing for stroke-patient friendly systems needs to consider the individual patients physical and cognitive impairments and produce an individualised experience.

What Helps or Hinders the Uptake of New Technologies into Rehabilitation Practice

Despite a proliferation of new rehabilitation technologies and a developing body of clinical evidence supporting their efficacy over the past 15 years, the uptake of rehabilitation technologies into clinical practice has been poor. In this qualitative study, we interviewed twenty seven rehabilitation clinicians to explore what helps and hinders the uptake of rehabilitation technologies into clinical practice. The findings illustrate that three inter-related factors are at play; the extent to which the technology addresses a clinical need, its clinical effectiveness and its usability. However, the interaction and weighting of these factors is influenced by the clinicians’ beliefs about the purpose of rehabilitation and what constitutes ‘valid’ rehabilitation practice, perceived professional roles, and whose perspective is given priority when evaluating technology. Understanding the context, process and values which drive decision-making may support the development of technologies which more readily translate into rehabilitation practice.

Upping the ante: working harder to address physical inactivity in older adults

Purpose of review Physical inactivity in older adults is associated with declining functional capacity, sarcopenia, metabolic changes, and cognitive changes. Current Physical Activity Guidelines recommend 150 min of moderate-intensity exercise along with strengthening and balance exercises. Despite the guidelines there is little evidence of a population-based change in physical activity. Recent findings There is a growing body of research investigating the use of high-intensity interval training in older adult to improve health-related outcomes. Research indicates that high-intensity interval training confers greater benefit than moderate-intensity exercise and is acceptable and safe for older adults and those with various noncommunicable diseases. Summary A major challenge to health systems is the growing number of people surviving into older age, many of whom have more than one noncommunicable disease. Physical inactivity is a modifiable risk factor for the development of noncommunicable diseases. Increasing participation in physical activity interventions, particularly those at a high intensity, appears to be a safe and feasible approach to reducing the demand on healthcare systems into the future.