Biology subjects

Boonstra, T. W.

Publications and source records attributed to Boonstra, T. W..

14 recordsLinked to original sources

bioRxiv2026

The Limited Range of Motion of the Knee Does Not Fully Explain the Altered Neural Control of Plantar Flexors During Gait in Non-Neurological Knee Flexion Contracture

Knee flexion contracture (KFC) may occur in the late stages of arthropathies, including osteoarthritis and haemophilic arthropathy. The impact of KFC on neuromuscular control remains unclear, particularly for the affected ankle plantar flexors. Surface electromyography (EMG) is widely used to assess muscle activation patterns, whereas intermuscular (EMG-EMG) coherence provides insight into common neural input. In this study we compared the neural control of ankle plantar flexors during gait between individuals with haemophilia and KFC (chronic; n = 8), and healthy individuals without (control; n = 15) and with an artificial constraint (artificial; n = 15). Bipolar EMG from plantar flexors was recorded during 30-m overground walking (1 m/s). Intermuscular coherence was estimated at 8-60 Hz during the stance phase and significance was determined using a permutation method. The chronic group showed greater knee flexion than controls (24-29 deg vs 2-20 deg), higher EMG amplitude at foot contact, and increased intermuscular coherence in the alpha (8-12 Hz) and beta (12-30 Hz) bands at mid-stance. Despite comparable sagittal knee kinematics between constrained conditions (chronic: 24-29 deg; artificial: 20-32 deg), early-stance EMG amplitude and mid-stance beta-band intermuscular coherence were higher in the chronic group across plantar-flexor pairs. Increased plantar-flexor activation in the chronic group suggests higher neural drive, while higher intermuscular coherence reflects greater common input to the plantar flexors. These findings indicate that limited ROM alone does not explain the altered neural control of plantar flexors, suggesting neural adaptations associated with non-neurological chronic KFC.

neuroscience↗

bioRxiv2025

Reduced belief updating impairs adaptive step initiation in older adults

Ageing is associated with declines in mobility and balance that threaten independence and increase fall risk. Although these changes are often attributed to deterioration of muscular and sensory systems, growing evidence suggests that age-related alterations in cognitive control also contribute to postural instability and gait impairments. Here, we examined whether shifts in cognitive control strategy underlie impaired gait initiation in older adults by modelling how individuals update beliefs about upcoming actions. Older and younger adults performed a choice-stepping go/no-go task in which step likelihood was manipulated across trials. We measured anticipatory postural adjustments (APAs), the preparatory weight shifts preceding stepping and modelled age-related differences in APA onset using a hierarchical Bayesian framework. Older adults initiated slower APAs, particularly after repeated go trials. Computational modelling revealed reduced learning rates and heightened sensitivity to uncertainty in older adults, identifying altered belief updating as a cognitive mechanism shaping age-related changes in adaptive stepping.

neuroscience↗

bioRxiv2023

Low-dimensional dynamics of brain-muscle networks during gait

Walking is a complex motor activity that requires coordinated interactions between sensory and motor systems. We used mobile EEG and EMG to investigate the brain-muscle networks involved in gait control during overground walking in young, older and individuals with Parkinsons Disease. Dynamic interactions between the sensorimotor cortices and eight leg muscles within a gait cycle were assessed using multivariate analysis. We identified three distinct brain-muscle networks during a gait cycle. These networks include a bilateral network, a left-lateralised network activated during the left swing phase, and a right-lateralised network active during right swing. The trajectories of these networks are contracted in older adults, indicating a reduction in neuromuscular connectivity with age. Individuals with impaired tactile sensitivity of the foot showed a selective enhancement of the bilateral network, possibly reflecting a compensation strategy to maintain gait stability. These findings provide a parsimonious description of interindividual differences in neuromuscular connectivity during gait. TeaserDynamic network analysis shows how brain-muscle connectivity during gait varies with age and somatosensory function.

neuroscience↗

bioRxiv2022

TDCS modulates working memory maintenance processes in healthy individuals

BackgroundThe effects of tDCS at the prefrontal cortex are often investigated using cognitive paradigms, particularly working memory tasks. However, the neural basis for the neuromodulatory cognitive effects of tDCS, including which subprocesses are affected by stimulation, is not completely understood. AimsWe investigated the effects of tDCS on working memory task-related spectral activity during and after tDCS to gain better insights into the neurophysiological changes associated with stimulation. MethodsWe reanalysed data from 100 healthy participants grouped by allocation to receive either Sham (0 mA, 0.016 mA, and 0.034 mA) or Active (1 mA or 2 mA) stimulation during a 3-back task. Electroencephalography (EEG) data was used to analyse event-related spectral power in frequency bands associated with working memory performance. ResultsFrontal theta event-related synchronisation (ERS) was significantly reduced post-tDCS in the active group. Participants receiving active tDCS had slower response times following tDCS compared to Sham, suggesting interference with practice effects associated with task repetition. Theta ERS was not significantly correlated with response times or accuracy. ConclusionstDCS reduced frontal theta ERS post-stimulation, suggesting a selective disruption to working memory cognitive control and maintenance processes. These findings suggest that tDCS selectively affects specific subprocesses during working memory, which may explain heterogenous behavioural effects.

neuroscience↗

bioRxiv2022

The effects of conscious movement processing on the neuromuscular control of posture

Maintaining balance is thought to primarily occur sub-consciously. Occasionally, however, individuals will direct conscious attention towards balance, e.g., in response to a threat to balance. Such conscious movement processing (CMP) increases the reliance on attentional resources and may disrupt balance performance. However, the underlying changes in neuromuscular control remain poorly understood. We investigated the effects of CMP (manipulated using verbal instructions) on neural control of posture in twenty-five adults (11 females, mean age = 23.9, range = 18-33). Participants performed 90-second, bipedal stance balance trials in high- and low-CMP conditions, during both stable (solid surface) and unstable (foam) task conditions. Postural sway amplitude, frequency and complexity were used to assess postural control. Surface EMG was recorded bilaterally from lower leg muscles (Soleus, Tibialis Anterior, Gastrocnemius Medialis, Peroneus Longus) and intermuscular coherence (IMC) was assessed for 12 muscle pairs across four frequency bands. We observed significantly increased sway amplitude, and decreased sway frequency and complexity in the high- compared to the low-CMP conditions. All sway variables increased in the unstable compared to the stable conditions. We observed reduced beta band IMC between several muscle pairs during high- compared to low-CMP, but these findings did not remain significant after controlling for multiple comparisons. Finally, IMC significantly increased in the unstable conditions for most muscle combinations and frequency bands. In all, results tentatively suggest that CMP-induced changes in sway outcomes may be facilitated by reduced beta-band IMC, but these findings need to be replicated before they can be interpreted more conclusively.

neuroscience↗

bioRxiv2021

Reliability of transcranial magnetic stimulation evoked potentials to detect the effects of theta-burst stimulation of the prefrontal cortex

BackgroundTranscranial magnetic stimulation (TMS) with simultaneous electroencephalography (EEG) is a novel method for assessing cortical properties outside the motor region. Theta burst stimulation (TBS), a form of repetitive TMS, can non-invasively modulate cortical excitability and has been increasingly used to treat psychiatric disorders by targetting the dorsolateral prefrontal cortex (DLPFC). The TMS-evoked potentials (TEPs) analysis has been used to evaluate cortical excitability changes after TBS. However, it remains unclear whether TEPs can detect the neuromodulatory effects of TBS. ObjectivesTo confirm the reliability of TEP components within and between sessions and to measure changes in neural excitability induced by intermittent (iTBS) and continuous TBS (cTBS) applied to the left DLPFC. MethodsTest-retest reliability of TEPs and TBS-induced changes in cortical excitability were assessed in twenty-four healthy participants by stimulating the DLPFC in five separate sessions, once with sham and twice with iTBS and cTBS. EEG responses were recorded of 100 single TMS pulses before and after TBS, and the reproducibility measures were quantified with the concordance correlation coefficient (CCC). ResultsThe N100 and P200 components presented substantial reliability within the baseline block (CCCs>0.8) and moderate concordance between sessions (CCCmax{approx}0.7). Both N40 and P60 TEP amplitudes showed little concordance between sessions. Changes in TEP amplitudes after iTBS were marginally reliable for N100 (CCCmax=0.52), P200 (CCCmax=0.47) and P60 (CCCmax=0.40), presenting only fair levels of concordance at specific time points. ConclusionsThe present findings show that only the N100 and P200 components had good concordance between sessions. The reliability of earlier components may have been affected by TMS-evoked artefacts. The poor reliability to detect changes in neural excitability induced by TBS indicates that TEPs do not provide a precise estimate of the changes in excitability in the DLPFC or, alternatively, that TBS did not induce consistent changes in neural excitability.

neuroscience↗

bioRxiv2021

The coordination of hip, knee and ankle joint angles during gait in soccer players and controls

BackgroundClinical researchers are trying to unravel the impact of different training interventions on the kinematics of human gait. However, the effects of long-term training experience on the kinematics of a healthy gait pattern remains unclear. Here we assess the effect of long-term training experience on joint angle variability during walking. MethodsHip, knee, and ankle joint angles from fourteen soccer players and sixteen controls were acquired during treadmill and overground walking. Hip-knee coupling, knee-ankle coupling and coupling angle variability (CAV) of the right leg in the sagittal plane were assessed using a vector coding technique. ResultsSoccer players showed reduced hip-knee CAV during the mid-stance and terminal-stance phases and reduced knee-ankle CAV during the pre-swing phase of gait compared to the control group. In addition, soccer players less often used an ankle coordination pattern, in which only the ankle joint but not the knee joint rotates. InterpretationThese findings show that soccer players had more stability in the ankle joint during the stance phase of the gait compared to the control group. Future studies can test whether these differences in the coordination of the ankle joint reflect the effects of long-term training on normal gait by comparing knee-ankle coupling and variability before and after exercise training interventions.

bioengineering↗

bioRxiv2021

Assessing neuromodulation effects of theta burst stimulation to the prefrontal cortex using TMS-evoked potentials

Theta burst stimulation (TBS), a form of repetitive transcranial magnetic stimulation (TMS), is capable of non-invasively modulating cortical excitability. TBS is gaining popularity as a therapeutic tool for psychiatric disorders such as depression, in which the dorsolateral prefrontal cortex (DLPFC) is the main therapeutic target. However, the neuromodulatory effects of TBS on prefrontal regions remain unclear. An emerging tool to assess neuromodulation in non-motor regions is concurrent transcranial magnetic stimulation and electroencephalography (TMS-EEG) to measure TMS-evoked potentials (TEPs). We assessed twenty-four healthy participants (13 males, mean age 25.2{+/-}9.9 years) following intermittent TBS, continuous TBS, and sham applied to the left DLPFC using a double-blinded crossover design. TEPs were obtained at baseline and 2-, 15-, and 30-min post-stimulation. Four TEP components (N40, P60, N100 and P200) were analysed using mixed effects repeated measures models (MRMM). Results indicate no significant effects for any assessed components (all p>.05). The largest effect size (Cohens d = -0.5) comparing iTBS and sham was obtained for the N100 component at 15 minutes post-stimulation. This result was in the same direction but smaller than found in previous studies, suggesting that the true effect size may be lower than previously reported. Accurate estimates of the effects sizes and inter-individual heterogeneity will critically inform clinical applications using TEPs to assess the neuromodulatory effects of TBS.

physiology↗

bioRxiv2021

The effects of long-term exercise training on the neural control of walking

How does long-term training modify the neural control of walking? Here we investigate changes in kinematics and muscle synergies of the lower extremities in 10 soccer players and 10 non-athletes while they walked with eyes open or closed either overground or on a treadmill. Electromyography (EMG) was acquired from eight muscles of the right leg and foot switch data were recorded to extract temporal gait parameters. Muscle synergies were extracted using non-negative matrix factorisation for each participant and condition separately and were then grouped using k-means clustering. We found that both the cycle and stance duration were longer during treadmill walking compared to overground walking, whereas the swing phase was longer during the eyes-open compare to the eyes-closed condition. On average, more synergies were expressed in the athlete compared to the non-athlete group and during treadmill compared to overground walking. We found that synergy 2 involved in ankle plantarflexion was more often activated in athletes than in non-athletes. We did not find statistical group differences for the synergy metrics but several differences were observed between conditions: peak activation of synergy 5 (VM and VL muscles) increased during overground walking compared to treadmill walking. In addition, reduced activation of synergy 3 (TA muscle) and synergy 4 was observed during eyes-closed compared to eyes-open walking. These findings suggest that during walking long-term training results in greater flexibility of muscle coordination by recruiting additional synergies, but we found no evidence that long-term training affects the activation patterns of these synergies.

neuroscience↗

bioRxiv2019

Corticomuscular control of walking in older people and people with Parkinson’s disease

Changes in human gait that result from ageing or neurodegenerative diseases are multifactorial. Here we assess the effects of age and Parkinsons disease (PD) on corticospinal control in electrophysiological activity recorded during treadmill and overground walking. Electroencephalography (EEG) from 10 electrodes and electromyography (EMG) from two leg muscles were acquired from 22 healthy young, 24 healthy older and 20 adults with PD. Event-related power, corticomuscular coherence (CMC) and inter-trial coherence were assessed for EEG from bilateral sensorimotor cortices and EMG from tibialis anterior muscles during the double support phase of the gait cycle. CMC and EMG power in the low beta band (13-21 Hz) was significantly decreased in older and PD participants compared to young people, but there was no difference between older and PD groups. Older and PD participants spent shorter time in the swing phase than young individuals. These findings indicate age-related changes in the temporal coordination of gait. The decrease in beta CMC suggests reduced cortical input to spinal motor neurons in older people during the double support phase. We also observed multiple changes in electrophysiological measures at high beta and low gamma frequencies during treadmill compared to overground walking, indicating task-dependent differences in corticospinal locomotor control.

neuroscience↗

bioRxiv2019

Information decomposition of multichannel EMG to map functional interactions in the distributed motor system

The central nervous system needs to coordinate multiple muscles during postural control. Functional coordination is established through the neural circuitry that interconnects different muscles. Here we used multivariate information decomposition of multichannel EMG acquired from 14 healthy participants during postural tasks to investigate the neural interactions between muscles. A set of information measures were estimated from an instantaneous linear regression model and a time-lagged VAR model fitted to the EMG envelopes of 36 muscles. We used network analysis to quantify the structure of functional interactions between muscles and compared them across experimental conditions. Conditional mutual information and transfer entropy revealed sparse networks dominated by local connections between muscles. We observed significant changes in muscle networks across postural tasks localized to the muscles involved in performing those tasks. Information decomposition revealed distinct patterns in task-related changes: unimanual and bimanual pointing were associated with reduced transfer to the pectoralis major muscles, but an increase in total information compared to no pointing, while postural instability resulted in increased information, information transfer and information storage in the abductor longus muscles compared to normal stability. These findings show robust patterns of directed interactions between muscles that are task-dependent and can be assessed from surface EMG recorded during static postural tasks. We discuss directed muscle networks in terms of the neural circuitry involved in generating muscle activity and suggest that task-related effects may reflect gain modulations of spinal reflex pathways.

neuroscience↗

bioRxiv2017

Effects of tDCS Dosage on Working Memory in Healthy Participants

BackgroundTranscranial direct current stimulation (tDCS) has been found to improve working memory (WM) performance in healthy participants following a single session. However, results are mixed and the overall effect size is small. Interpretation of these results is confounded by heterogeneous study designs, including differences in tDCS dose (current intensity) and sham conditions used.\n\nAimsWe systematically investigated the effect of tDCS dose on working memory using behavioural and neurophysiological outcomes.\n\nMethodsIn a single-blind parallel group design, 100 participants were randomised across five groups to receive 15 minutes of bifrontal tDCS at different current intensities (2mA, 1mA, and three sham tDCS conditions at 0.034mA, 0.016mA, or 0mA). EEG activity was acquired while participants performed a WM task prior to, during, and following tDCS. Response time, accuracy and an event-related EEG component (P3) were evaluated.\n\nResultsWe found no significant differences in response time or performance accuracy between current intensities. The P3 amplitude was significantly lower in the 0mA condition compared to the 0.034mA, 1mA and 2mA tDCS conditions. Changes in WM accuracy were moderately correlated with changes in the P3 amplitude following tDCS compared to baseline levels (r = 0.34).\n\nConclusionsWorking memory was not significantly altered by tDCS, regardless of dose. The P3 amplitude showed that stimulation at 1mA, 2mA and a sham condition (0.034mA) had biological effects, with the largest effect size for 1mA stimulation. These findings indicate higher sensitivity of neurophysiological outcomes to tDCS and suggests that sham stimulation previously considered inactive may alter neuronal function.

neuroscience↗

bioRxiv2017

Network structure of the human musculoskeletal system shapes neural interactions on multiple timescales

Human motor control requires the coordination of muscle activity under the anatomical constraints imposed by the musculoskeletal system. Interactions within the central nervous system are fundamental to motor coordination, but the principles governing functional integration remain poorly understood. We used network analysis to investigate the relationship between anatomical and functional connectivity amongst 36 muscles. Anatomical networks were defined by the physical connections between muscles and functional networks were based on intermuscular coherence assessed during postural tasks. We found a modular structure of functional networks that was strongly shaped by the anatomical constraints of the musculoskeletal system. Changes in postural tasks were associated with a frequency-dependent reconfiguration of the coupling between functional modules. These findings reveal distinct patterns of functional interactions between muscles involved in flexibly organising muscle activity during postural control. Our network approach to the motor system offers a unique window into the neural circuitry driving the musculoskeletal system.

neuroscience↗

bioRxiv2017

Dynamics of corticospinal motor control during overground and treadmill walking in humans

Increasing evidence suggests cortical involvement in the control of human gait. However, the nature of corticospinal interactions remains poorly understood. We performed time-frequency analysis of electrophysiological activity acquired during treadmill and overground walking in 22 healthy, young adults. Participants walked at their preferred speed (4.2, SD 0.4 km h-1), which was matched across both gait conditions. Event-related power, corticomuscular coherence (CMC) and inter-trial coherence (ITC) were assessed for EEG from bilateral sensorimotor cortices and EMG from the bilateral tibialis anterior (TA) muscles. Cortical power, CMC and ITC at theta, alpha, beta and gamma frequencies (4-45 Hz) increased during the double support phase of the gait cycle for both overground and treadmill walking. High beta (21-30 Hz) CMC and ITC of EMG was significantly increased during overground compared to treadmill walking, as well as EEG power in theta band (4-7 Hz). The phase spectra revealed positive time lags at alpha, beta and gamma frequencies, indicating that the EEG response preceded the EMG response. The parallel increases in power, CMC and ITC during double support suggest evoked responses at spinal and cortical populations rather than a modulation of ongoing corticospinal oscillatory interactions. The evoked responses are not consistent with the idea of synchronization of ongoing corticospinal oscillations, but instead suggest coordinated cortical and spinal inputs during the double support phase. Frequency-band dependent differences in power, CMC and ITC between overground and treadmill walking suggest differing neural control for the two gait modalities, emphasizing the task-dependent nature of neural processes during human walking.\n\nNew & NoteworthyWe investigated cortical and spinal activity during overground and treadmill walking in healthy adults. Parallel increases in power, CMC and ITC during double support suggest evoked responses at spinal and cortical populations rather than a modulation of ongoing corticospinal oscillatory interactions. These findings identify neurophysiological mechanisms that are important for understanding cortical control of human gait in health and disease.

physiology↗