Efficacy of a Single-Task ERP Measure to Evaluate Cognitive Workload During a Novel Exergame

This study aimed to validate the efficacy of single-task event-related potential (ERP) measures of cognitive workload to be implemented in exergame-based rehabilitation. Twenty-four healthy participants took part in a novel gamified balance task where task-irrelevant auditory tones were presented in the background to generate ERPs in the participants’ electroencephalogram (EEG) as a measure of cognitive workload. For the balance task, a computer-based tilt-ball game was combined with a balance board. Participants played the game by shifting their weight to tilt the balance board, which moved a virtual ball to score goals. The game was manipulated by adjusting the size of the goalposts to set three predefined levels of game difficulty (easy, medium, and hard). The participant’s experience of game difficulty was evaluated based on the number of goals scored and their subjective reporting of perceived difficulty. Participants experienced a significant difference in the three levels of task difficulty based on the number of goals scored and perceived difficulty (p < 0.001). Post hoc analysis revealed the lowest performance for the hardest level. The mean amplitude of the N1 ERP component was used to measure the cognitive workload associated with the three difficulty levels. The N1 component’s amplitude decreased significantly (p < 0.001), with an increase in the task difficulty. Moreover, the amplitude of the N1 component for the hard level was significantly smaller compared to medium (p = 0.0003) and easy (p < 0.001) levels. These results support the efficacy of the N1 ERP component to measure cognitive workload in dynamic and real-life scenarios such as exergames and other rehabilitation exercises

Strength for Task Training: a novel intervention to improve locomotor ability following stroke

Many people with stroke have ongoing difficulty with locomotor abilities to the extent that it limits their participation in meaningful community life. Deficits in locomotor ability are strongly related to muscle weakness following stroke. Whilst the majority of physical therapy time is spent on the rehabilitation of locomotor abilities, the most effective rehabilitation method has yet to be determined. The need to develop efficacious rehabilitation strategies to address locomotor disability following stroke is paramount. Therefore, the primary aim of this thesis was the development of a novel intervention to improve locomotor ability in people following stroke. Systematic reviews of the evidence base were undertaken, evaluating two rehabilitation interventions; strength training and task-specific training. It was identified that strength training results in considerable increases in muscle strength. Yet despite the strong relationship between strength and locomotor ability, gains in strength following strength training translate poorly into improvements in locomotor ability. In considering task-specific training, the findings indicate that it improves locomotor ability; however gains are modest at best. These reviews suggested that the limited outcomes seen may relate to a failure to train people with stroke at sufficient intensity and dose, and with specificity to locomotor disability. A narrative review of the neuroscience literature in relation to the neural control of walking and neural plasticity elucidated a role for strength training to act as a priming intervention prior to task-specific training in people with stroke. Collectively this information informed the development of a novel intervention to improve locomotor ability following stroke; Strength for Task Training (STT). The key features of STT are that strength training is utilised to systematically prime the central nervous system prior to task-specific training and that strength training and task-specific training are conducted in an evidence based manner to maximise gains in locomotor ability. As part of the development of the STT intervention and preparation for evaluation, the selection of valid and reliable outcome measures was considered. The identification of suitable measures of the neural plasticity underlying recovery proved challenging. Therefore, a feasibility assessment of potential outcome measures was undertaken, identifying two possibilities; Transcranial magnetic stimulation (TMS) derived measures of corticomotor excitability and serum measurement of the neurotrophin, brain derived neurotropic factor (BDNF). In order to establish the test-retest reliability of these measures, two repeated measures studies were undertaken. These studies established the excellent test-retest reliability of TMS-derived measures when taken during treadmill walking. However, BDNF proved a less reliable measure. The final study of this thesis was a mixed methods pilot study which evaluated the feasibility of the research protocol for testing the STT intervention in a randomized controlled trial and the acceptability of the STT intervention to people with stroke and physiotherapists. This pilot study established the feasibility of the sampling and recruitment strategy, the integrity of the trial protocol and the feasibility, acceptability and safety of the STT intervention. The rigorous implementation of this mixed methods pilot study enabled refinement of both the study protocol and intervention, safeguarding the success of future evaluation in a large randomised controlled trial and translation of this novel intervention into clinical practice

Reliability of Tibialis Anterior Muscle Voluntary Activation Using the Interpolated Twitch Technique and the Central Activation Ratio in People with Stroke

Voluntary activation (VA) is measured by applying supramaximal electrical stimulation to a muscle during a maximal voluntary contraction (MVC). The amplitude of the evoked muscle twitch is used to determine any VA deficit, and indicates incomplete central neural drive to the motor units. People with stroke experience VA deficits and greater levels of central fatigue, which is the decrease in VA that occurs following exercise. This study investigated the between-session reliability of VA and central fatigue of the tibialis anterior muscle (TA) in people with chronic stroke (n = 12), using the interpolated twitch technique (ITT), adjusted-ITT, and central activation ratio (CAR) methods. On two separate sessions, supramaximal electrical stimulation was applied to the TA when it was at rest and maximally activated, at the start and end of a 30-s isometric dorsiflexor MVC. The most reliable measures of VA were obtained using the CAR calculation on transformed data, which produced an ICC of 0.92, and a lower bound confidence interval in the good range (95% CI 0.77 to 0.98). Reliability was lower for the CAR calculation on non-transformed data (ICC 0.82, 95% CI 0.63 to 0.91) and the ITT and adjusted-ITT calculations on transformed data (ICCs 0.82, 95% CIs 0.51 to 0.94), which had lower bound confidence intervals in the moderate range. The two ITT calculations on non-transformed data demonstrated the poorest reliability (ICCs 0.62, 95% CI 0.25 to 0.74). Central fatigue measures demonstrated very poor reliability. Thus, the reliability for VA in people with chronic stroke ranged from good to poor, depending on the calculation method and statistical analysis method, whereas the reliability for central fatigue was very poor

Characteristics of the Contingent Negative Variation during Lower Limb Functional Movement with an Audio-Visual Cue

Background: The contingent negative variation (CNV) is a negative shift in electroencephalography (EEG) related to the planning and execution of an externally cued movement task. The CNV has the potential to be applied within stroke rehabilitation; however, there is insufficient knowledge about the CNV characteristics under movement conditions relevant to rehabilitation. This study explores the CNV characteristics during a functional movement task (versus a simple movement task) and when using an audio-visual cue that has been previously evaluated for its usability in stroke rehabilitation (versus a simple visual cue). Methods: Thirty healthy participants performed five randomized movement tasks: simple ankle dorsiflexion with a visual cue (1), audio-visual cue (2), and auditory-only cue (3), and sit-to-stand with a visual (4) and audio-visual cue (5). Fifty repetitions of each movement were performed while continuous EEG was recorded. The band-passed and Laplacian-filtered (Cz) EEG was averaged for each condition and the peak negativity (PN) latency and amplitude were identified. Results: PN latency was significantly later during sit-to-stand with the audio-visual cue versus the visual cue (p = 0.027). PN amplitude was significantly larger during sit-to-stand versus ankle dorsiflexion, with both visual and audio-visual cues (p < 0.0001). Conclusion: The CNV changes under more complex movement conditions. Assumptions about the MRCP from simple laboratory recordings should not be generalized to the rehabilitation setting

Electroencephalographic recording of the movement-related cortical potential in ecologically-valid movements:A scoping review

The movement-related cortical potential (MRCP) is a brain signal that can be recorded using surface electroencephalography (EEG) and represents the cortical processes involved in movement preparation. The MRCP has been widely researched in simple, single-joint movements, however, these movements often lack ecological validity. Ecological validity refers to the generalizability of the findings to real-world situations, such as neurological rehabilitation. This scoping review aimed to synthesize the research evidence investigating the MRCP in ecologically valid movement tasks. A search of six electronic databases identified 102 studies that investigated the MRCP during multi-joint movements; 59 of these studies investigated ecologically valid movement tasks and were included in the review. The included studies investigated 15 different movement tasks that were applicable to everyday situations, but these were largely carried out in healthy populations. The synthesized findings suggest that the recording and analysis of MRCP signals is possible in ecologically valid movements, however the characteristics of the signal appear to vary across different movement tasks (i.e., those with greater complexity, increased cognitive load, or a secondary motor task) and different populations (i.e., expert performers, people with Parkinson’s Disease, and older adults). The scarcity of research in clinical populations highlights the need for further research in people with neurological and age-related conditions to progress our understanding of the MRCPs characteristics and to determine its potential as a measure of neurological recovery and intervention efficacy. MRCP-based neuromodulatory interventions applied during ecologically valid movements were only represented in one study in this review as these have been largely delivered during simple joint movements. No studies were identified that used ecologically valid movements to control BCI-driven external devices; this may reflect the technical challenges associated with accurately classifying functional movements from MRCPs. Future research investigating MRCP-based interventions should use movement tasks that are functionally relevant to everyday situations. This will facilitate the application of this knowledge into the rehabilitation setting

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 at varying intensities during four conditions. Twelve healthy subjects performed 50 dorsiflexions at the ankle during nerve or muscle ES at motor threshold. 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 minutes 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

Associative cued asynchronous BCI induces cortical plasticity in stroke patients

OBJECTIVE: We propose a novel cue‐based asynchronous brain–computer interface(BCI) for neuromodulation via the pairing of endogenous motor cortical activity with the activation of somatosensory pathways. METHODS: The proposed BCI detects the intention to move from single‐trial EEG signals in real time, but, contrary to classic asynchronous‐BCI systems, the detection occurs only during time intervals when the patient is cued to move. This cue‐based asynchronous‐BCI was compared with two traditional BCI modes (asynchronous‐BCI and offline synchronous‐BCI) and a control intervention in chronic stroke patients. The patients performed ankle dorsiflexion movements of the paretic limb in each intervention while their brain signals were recorded. BCI interventions decoded the movement attempt and activated afferent pathways via electrical stimulation. Corticomotor excitability was assessed using motor‐evoked potentials in the tibialis‐anterior muscle induced by transcranial magnetic stimulation before, immediately after, and 30 min after the intervention. RESULTS: The proposed cue‐based asynchronous‐BCI had significantly fewer false positives/min and false positives/true positives (%) as compared to the previously developed asynchronous‐BCI. Linear‐mixed‐models showed that motor‐evoked potential amplitudes increased following all BCI modes immediately after the intervention compared to the control condition (p <0.05). The proposed cue‐based asynchronous‐BCI resulted in the largest relative increase in peak‐to‐peak motor‐evoked potential amplitudes(141% ± 33%) among all interventions and sustained it for 30 min(111% ± 33%). INTERPRETATION: These findings prove the high performance of a newly proposed cue‐based asynchronous‐BCI intervention. In this paradigm, individuals receive precise instructions (cue) to promote engagement, while the timing of brain activity is accurately detected to establish a precise association with the delivery of sensory input for plasticity induction

“Physical well-being is our top priority”: Healthcare professionals' challenges in supporting psychosocial well-being in stroke services

Background Following stroke, a sense of well-being is critical for quality of life. However, people living with stroke, and health professionals, suggest well-being is not sufficiently addressed within stroke services, contributing to persistent unmet needs. Knowing that systems and structures shape clinical practice, this study sought to understand how health professionals address well-being, and to examine how the practice context influences care practice. Methods Underpinned by Interpretive Description methodology, we interviewed 28 health professionals across multiple disciplines working in stroke services (acute and rehabilitation) throughout New Zealand. Data were analysed using Applied Tensions Analysis. Results Health professionals are managing multiple lines of work in stroke care: biomedical work of investigation, intervention and prevention; clinical work of assessment, monitoring and treatment; and moving people through service. While participants reported working to support well-being, this could be deprioritised amidst the time-oriented pressures of the other lines of work that were privileged within services, rendering it unsupported and invisible. Conclusion Stroke care is shaped by biomedical and organisational imperatives which privilege physical recovery and patient throughput. Health professionals are not provided with the knowledge, skills, time or culture of care that enable them to privilege well-being within their work. This has implications for the well-being of people with stroke, and the well-being of health professionals. In making these discourses and culture visible, and tracing how these impact on clinical practice, we hope to provide insight into why well-being work remains other to the ‘core’ work of stroke, and what needs to be considered if stroke services are to better support people’s well-being. Patient or public contributions People with stroke, family members, and people who provide support to people with stroke, and health professionals set priorities for this research. They advised on study conduct and have provided feedback on wider findings from the research