Clayton Winford Swanson

Multiple sclerosis (MS) often leads to mobility impairments, yet the neural mechanisms underlying these deficits remain poorly understood. This study examined whether resting-state functional connectivity (rs-FC) differs between people with MS (PwMS) and healthy controls in relation to spatiotemporal mobility performance. We hypothesized that group differences within the default mode (DMN), frontoparietal (FPN), somatomotor (SN), and visual (VIS) networks would be associated with gait and turning metrics. Twenty-nine PwMS and 28 matched controls completed a two-minute walk test, 180° walking turns, and 360° in-place turns at natural and fast speeds. fMRI data were analyzed using multivariate pattern analysis (MVPA) and post-hoc seed-to-voxel analyses for gait speed, cadence, double support time, stride length, turn duration, peak velocity, and turn angle. PwMS exhibited slower gait speed, shorter stride length, and impaired 360° turning, but no group differences in cadence, double support, or 180° turn metrics. MVPA revealed rs-FC differences across DMN, FPN, SN, and VIS networks. While rs-FC differences were evident for walking metrics, within-group associations were not significant. In contrast, 360° turn angle showed distinct within-group rs-FC associations, particularly involving VAN and DAN networks. These findings highlight turning as a sensitive task for capturing functional neural differences in MS.

Declines in walking function commonly occur in people with multiple sclerosis (MS). Walking is a continuous movement and a complex motor task that requires precise timing and scaling of activation across many muscles. The objectives of this study were to identify kinematic gait characteristics during a 2-minute walk test that are associated with disease duration in individuals with relapsing-remitting MS (n=45). Participants were instrumented with inertial measurement units from APDM (APDM Inc, Portland, OR, USA) and performed the 2-minute walk test twice: once at their self-selected speed and another at their fastest, safe speed. Gait speed was not associated with MS disease duration (Self-selected: p= 0.180; Fast: p=0.167). Canonical correlation analysis showed that disease progression was strongly associated with lateral step width variability and ankle pitch at toe-off, which was also reflected in the multiple linear regression models. Both self-selected and fast-speed kinematics were associated with disease duration (Self-selected: p=0.007; Fast: p=0.004). Thus, we identified a multivariate model that is associated with disease duration in highly ambulatory MS individuals. Our study highlights the importance of considering individual differences in specific gait kinematics (such as lateral step width variability and ankle pitch at toe-off) when assessing disease progression in MS. This approach may provide more personalized insights into the impact of MS on mobility and help tailor interventions to improve gait and overall function in affected individuals. Future research should continue exploring these kinematic parameters to better understand their role in MS progression and develop targeted therapeutic strategies.

Background: Several changes occur in the central nervous system with increasing age that contribute toward declines in mobility. Neurorehabilitation has proven effective in improving motor function though achieving sustained behavioral and neuroplastic adaptations is more challenging. While effective, rehabilitation usually follows adverse health outcomes, such as injurious falls. This reactive intervention approach may be less beneficial than prevention interventions. Therefore, we propose the development of a prehabilitation intervention approach to address mobility problems before they lead to adverse health outcomes. This protocol article describes a pilot study to examine the feasibility and acceptability of a home-based, self-delivered prehabilitation intervention that combines motor imagery (mentally rehearsing motor actions without physical movement) and neuromodulation (transcranial direct current stimulation, tDCS; to the frontal lobes). A secondary objective is to examine preliminary evidence of improved mobility following the intervention. Methods: This pilot study has a double-blind randomized controlled design. Thirty-four participants aged 70–95 who self-report having experienced a fall within the prior 12 months or have a fear of falling will be recruited. Participants will be randomly assigned to either an active or sham tDCS group for the combined tDCS and motor imagery intervention. The intervention will include six 40-min sessions delivered every other day. Participants will simultaneously practice the motor imagery tasks while receiving tDCS. Those individuals assigned to the active group will receive 20 min of 2.0-mA direct current to frontal lobes, while those in the sham group will receive 30 s of stimulation to the frontal lobes. The motor imagery practice includes six instructional videos presenting different mobility tasks related to activities of daily living. Prior to and following the intervention, participants will undergo laboratory-based mobility and cognitive assessments, questionnaires, and free-living activity monitoring. Discussion: Previous studies report that home-based, self-delivered tDCS is safe and feasible for various populations, including neurotypical older adults. Additionally, research indicates that motor imagery practice can augment motor learning and performance. By assessing the feasibility (specifically, screening rate (per month), recruitment rate (per month), randomization (screen eligible who enroll), retention rate, and compliance (percent of completed intervention sessions)) and acceptability of the home-based motor imagery and tDCS intervention, this study aims to provide preliminary data for planning larger studies. Trial registration: This study is registered on ClinicalTrials.gov (NCT05583578). Registered October 13, 2022. https://www.clinicaltrials.gov/study/NCT05583578

Multiple sclerosis is accompanied by decreased mobility and various adaptations affecting neural structure and function. Therefore, the purpose of this project was to understand how motor cortex thickness and corticospinal excitation and inhibition contribute to turning performance in healthy controls and people with multiple sclerosis. In total, 49 participants (23 controls, 26 multiple sclerosis) were included in the final analysis of this study. All participants were instructed to complete a series of turns while wearing wireless inertial sensors. Motor cortex gray matter thickness was measured via magnetic resonance imaging. Corticospinal excitation and inhibition were assessed via transcranial magnetic stimulation and electromyography place on the tibialis anterior muscles bilaterally. People with multiple sclerosis demonstrated reduced turning performance for a variety of turning variables. Further, we observed significant cortical thinning of the motor cortex in the multiple sclerosis group. People with multiple sclerosis demonstrated no significant reductions in excitatory neurotransmission, whereas a reduction in inhibitory activity was observed. Significant correlations were primarily observed in the multiple sclerosis group, demonstrating lateralization to the left hemisphere. The results showed that both cortical thickness and inhibitory activity were associated with turning performance in people with multiple sclerosis and may indicate that people with multiple sclerosis rely on different neural resources to perform dynamic movements typically associated with fall risk.

As the populations of the United States and developed nations age, motor control performance is adversely impacted, resulting in functional impairments that can diminish quality of life. Generally, force control in the lower limb worsens with age, with older adults (OA) displaying more variable and less accurate submaximal forces. Corticospinal inhibitory signaling may influence force control, with those OA who maintain corticospinal inhibitory signaling capacity achieving steadier forces. This study aimed to assess the relationships between lower limb force control and transcranial magnetic stimulation (TMS) measures of corticospinal inhibition (i.e., cortical silent period (cSP) duration and depth). 15 OA and 14 young adults (YA) were recruited for this study. All subjects underwent a TMS protocol to elicit the cSP while maintaining 15% of their maximal force in their knee extensor muscles. OA and YA did not display differences in force control metrics or corticospinal inhibitory measures. However, in OA, maximal cSP depth (%dSP max) was associated with lower force variability. No other significant relationships existed in the YA or OA groups. Future studies will benefit from evaluating a range of target forces and target muscles to assess potential relationships between sensorimotor inhibitory capacity and control of muscle force output.

Age-related mobility research often highlights significant mobility differences comparing neurotypical young and older adults, while neglecting to report mobility outcomes for middle-aged adults. Moreover, these analyses regularly do not determine which measures of mobility can discriminate groups into their age brackets. Thus, the current study aimed to provide a comprehensive analysis for commonly performed aspects of mobility (walking, turning, sit-to-stand, and balance) to determine which variables were significantly different and furthermore, able to discriminate between neurotypical young adults (YAs), middle-aged adults (MAAs), and older adults (OAs). This study recruited 20 YAs, 20 MAAs, and 20 OAs. Participants came into the laboratory and completed mobility testing while wearing wireless inertial sensors. Mobility tests assessed included three distinct two-minute walks, 360° turns, five times sit-to-stands, and a clinical balance test, capturing 99 distinct mobility metrics. Of the various mobility tests assessed, only 360° turning measures demonstrated significance between YAs and MAAs, although the capacity to discriminate between groups was achieved for gait and turning measures. A variety of mobility measures demonstrated significance between MAAs and OAs, and furthermore discrimination was achieved for each mobility test. These results indicate greater mobility differences between MAAs and OAs, although discrimination is achievable for both group comparisons.

Context: In longitudinal studies tracking recovery after concussion, researchers often have not considered the timing of return to play (RTP) as a factor in their designs, which can limit the understanding of how RTP may affect the analysis and resulting conclusions. Objective: To evaluate the recovery of balance and gait in concussed athletes using a novel linear mixed-model design that allows an inflection point to account for changes in trend that may occur after RTP. Design: Cohort study. Setting: University athletics departments, applied field setting. Patients or Other Participants: Twenty-three concussed (5 women, 18 men; age = 20.1 ± 1.3 years) and 25 healthy control (6 women, 19 men; age = 20.9 ± 1.4 years) participants were studied. Participants were referred by their team athletic trainers. Main Outcome Measure(s): Measures consisted of the Balance Error Scoring System (BESS) total score, sway (instrumented root mean square of mediolateral sway), single-task gait speed, gait speed while simultaneously reading a handheld article (dual-task gait speed), dual-task cost of reading on gait speed, and dual-task cost of walking on reading. Results: We observed no significant effects or interactions for the BESS. Instrumented sway was worse in concussed participants, and a change in the recovery trend occurred after RTP. We observed group and time effects and group × time and group × RTP change interactions (P ≤ .046). No initial between-groups differences were found for single-task or dual-task gait. Both groups increased gait speed initially and then leveled off after the average RTP date. We noted time and RTP change effects and positive group × time interactions for both conditions (P ≤ .042) and a group × RTP change interaction for single-task gait speed (P = .005). No significant effects or interactions were present for the dual-task cost of reading on gait speed or the dual-task cost of walking on reading. Conclusions: Changes in the rate of recovery were coincident with the timing of RTP. Although we cannot suggest these changes were a result of the athletes returning to play, these findings demonstrate the need for further research to evaluate the effects of RTP on concussion recovery.