Biology subjects

Lamoth, C. J. C.

Publications and source records attributed to Lamoth, C. J. C..

3 recordsLinked to original sources

bioRxiv2025

The Effect of Physical Activity Level on Age-Related Differences in Responses to Optic Flow Perturbation during Human Walking

BackgroundHuman aging increases the reliance on vision for walking balance due to age-related declines in proprioceptive and vestibular function. Regular physical activity (PA) may reduce the reliance on visual input during walking. This study examined whether PA levels modulate age-related responses to perturbations of the optic flow that is crucial in the control of human locomotion. MethodsSixty active and inactive younger (YA and YI: 23.3{+/-}3.91 y) and older adults (OA and OI: 68.3{+/-}3.98 y; n=15 for each group) walked on a treadmill in front of a virtual hallway. The walking protocol consisted of 3-minute walking without, and 8-minute with mediolateral optic flow perturbation. Sacrum and heel marker positions and ground reaction forces were recorded. Power spectral density (PSD) of the mediolateral sacrum position and gait parameters were analyzed. ResultsThe PSD increased more in OA compared to OI adults (p=0.041) while YA and YI adults did not differ. Mean (and variability of) step width and mediolateral margin of stability increased irrespective of age and PA (all p<0.001). During the 8-minute perturbation, OA adults demonstrated greater decreases in PSD than the OI adults (p=0.039). Additionally, the variability in the mediolateral margin of stability reduced more in YA and OA adults compared to YI and OI adults (p=0.048). ConclusionHigher PA levels in OA adults were associated with stronger immediate responses in body sway to optic flow perturbations compared to older inactive and younger adults. This may support the beneficial effects of physical activity on age-related visual dependency during gait.

neuroscience↗

bioRxiv2025

Neurophysiological correlates of passive movements are speed- and type-dependent

IntroductionThe supraspinal involvement in the control of passive movements remains elusive. Mechanoreceptor properties, their change in the context of ageing and the somatotopically organized supraspinal connections between sensory and motor systems provide a neuroanatomical basis for the prediction that cortical structures are involved in the control of passive movements. Previous electromyographic evidence indeed show movement speed and - type-dependent changes in muscle activity. This study aimed to provide electrophysiological evidence for the involvement of frontal cortex inhibition and corticomotor interactions in the control of passive movements. MethodsContinuous and discontinuous passive elbow movements were performed in healthy younger (n = 20, 22.5 {+/-} 2.31 y) and older (n = 20, 72.7 {+/-} 5.73 y) adults at three movement speeds (20, 60, and 100 bpm) while electro-encephalographic (EEG) and electromyographic (EMG) data were acquired. Alpha power and beta corticomuscular connectivity were used as measures of frontal cortex inhibition and brain-muscle connectivity, respectively. ResultsFrontal cortex inhibition decreased (p = 0.036) and brain-muscle connectivity increased (p < 0.001) with increasing movement speeds. In addition, frontal cortex inhibition was 17% higher in the discontinuous condition as compared to the continuous condition (p = 0.005) while corticomuscular coherence was 25.9% higher in the continuous vs. the discontinuous condition (p < 0.001). These effects were independent of age. ConclusionThe present results provide insights into the control of passive movements and show that frontal cortex inhibition and brain-muscle interactions depend on movement speed and movement type.

neuroscience↗

bioRxiv2025

The effects of gait speed on the responses to immediate and prolonged exposure to mediolateral optic flow perturbation in healthy young adults

BackgroundOptic flow is vital for locomotor control and is often perturbed to study the impact of optic flow on balance control. However, it remains unclear whether gait speed influences responses to such perturbations. This study aims to examine the effects of gait speed on gait parameters following immediate and prolonged exposure to mediolateral optic flow perturbations. MethodsTwenty-one young adults (23.43 {+/-} 4.19 years) walked on an instrumented treadmill, including 3 phases: baseline (3 min), perturbation with mediolateral optic flow (8 min), and post-perturbation (3 min). Trials were conducted at 0.6, 1.2, and 1.8 m/s. Ground reaction forces and 3D motion data were collected to calculate mediolateral margin of stability (MoS), mean step length (SL), step width (SW) and their variabilities. Three repeated-measures ANOVAs (Speed by Phase) were used to compare: baseline vs. early perturbation, early vs. late perturbation, and baseline vs. post-perturbation. ResultsThe responses to immediate and prolonged exposure to optic flow perturbation were speed dependent. Walking at slow speeds induced greater immediate responses in mediolateral gait parameters (SW and mediolateral MoS, both p < 0.001) compared to walking at faster speeds. During the perturbation phase, the adaptations were larger at faster vs. slower speeds for gait parameters in the direction of movement (SL, p = 0.007). ConclusionImmediate responses and adaptations to mediolateral optic flow perturbations are speed-dependent and larger at slower gait speeds. The responses to prolonged perturbation are interpreted as step-to-step adaptations that may inform future interventions and studies on gait speed selection.

neuroscience↗