Peter C. Fino

Sleep deprivation (SDEP) impairs cognitive control, which may affect movements that rely on these processes, such as walking. To test whether gait changes after one night of SDEP reflect reduced cognitive capacity, we compared its effects with those of dual-task walking (i.e. walking while performing a simultaneous cognitive task). We hypothesize that SDEP will produce gait changes similar to those under dual-task conditions. Eighteen healthy adults (nine female, nine male; age, mean (s.d.): 22.2 (2.3) years) were tested the morning after a SDEP and a control night. Participants completed two 2-minute trials: single-task walking and walking with a concurrent 2-back working memory task (DT, dual-task walking). Using lateral foot and pelvis marker trajectories, we calculated spatio-temporal parameters, foot placement error in anteroposterior (FPEAP) and mediolateral (FPEML) directions, and mediolateral margin of stability (MoSML). SDEP increased average step time (p < 0.001) and step length (p = 0.002), and DT reduced spatio-temporal variability. Both SDEP (p = 0.004) and DT (p < 0.001) reduced FPEAP, but only DT reduced FPEML (p < 0.001). Additionally, mean MoSML decreased only in SDEP (p = 0.025). Overall, these findings suggest that while SDEP and dual-tasking both affect gait, the effects of SDEP on gait cannot be fully explained by reduced cognitive resources.

Humans regularly walk across uneven terrain, which demands reactive control strategies to maintain forward progress and stability. While reactive control during walking has been well described during straight gait, it is unclear how reactive control differs during turning gait. Because turning is asymmetrical, perturbations to the inside and outside limbs may elicit different reactive adjustments. This study investigates how unexpected underfoot perturbations alter stability measures during turning and how individuals alter their foot placement to maintain stability after such perturbations. Seven healthy adults completed walking trials around a circular track while wearing mechanized shoes that pseudo-randomly delivered underfoot perturbations to either the inside or outside limb. We calculated mediolateral margin of stability corrected for centripetal acceleration (ML MoSC), step width and step length from kinematic data. Linear mixed effects models compared the effects of perturbation type (inversion versus eversion) and perturbed limb (inside versus outside) for each outcome measure. ML MoSC was affected by both perturbation type and perturbed limb, with larger changes observed during eversion and outside limb perturbations. Changes to step width and step time during two recovery steps after each perturbation were primarily influenced by the perturbed limb – outside limb perturbations elicited consistent changes during two recovery steps compared with one altered step after inside limb perturbations. Perturbations to the outside limb during turning disrupted gait longer than perturbations to the inside limb. This difference across perturbed limb may indicate that outside steps are more important than inside ones for maintaining and recovering stability during turning.

Traumatic brain injury (TBI) mechanisms are often grouped together in research. Differences in acute and long-term outcomes across mechanisms of injury (MOIs) remain unclear, partly because of confounding by age. Modeling MOI-specific effects can inform clinical triage and prognostication. We examined the relationship between motor vehicle accidents (MVAs) vs falls, the 2 most common MOIs, and acute and 1-year post-injury outcomes, after rigorous control of demographic and preinjury personal factors. Data were analyzed from individuals with moderate-to-severe TBI requiring inpatient rehabilitation from the TBI Model Systems National Database, a multicenter prospective longitudinal cohort study. The analytic sample was restricted to individuals aged 16-79 years with an MOI due to MVA or fall occurring between April 2010 and January 2023. We used inverse probability of treatment weighting, based on propensity scores, to adjust for 14 demographic and preinjury personal characteristics and estimate the causal effect of MOI on acute and 1-year outcomes after TBI. Acute hospital and rehabilitation outcomes included the following: Glasgow Coma Scale (GCS), sedation, intubation, post-traumatic amnesia duration, time to follow commands (TFC), length of hospital stay (LOS), and Functional Independence Measure (FIM) cognitive and motor scores. One-year outcomes included the following: Disability Rating Scale and Participation Assessment with Recombined Tools Objective. Among 5,181 participants (mean age 45.1 ± 19.5, 70% male), 48.4% sustained their injury from MVAs and 51.6% from falls. After weighting and multiple comparisons adjustment, the MVA group had lower GCS total scores by 1.27 points (95% CI -1.92 to -0.61; adjusted p = 0.001), greater odds of receiving sedation (odds ratio 1.43, 95% CI 1.11-1.85; adjusted p = 0.014), longer TFC by 1.64 days (95% CI 0.39-2.89; adjusted p = 0.017), and lower discharge FIM motor scores by 4.28 points (95% CI -7.50 to -1.26; adjusted p = 0.014). At 1 year after injury, disability levels and community participation did not differ. MVA-related TBI was associated with worse acute outcomes. However, by 1 year after injury, disability level and community participation do not differ. This work highlights novel findings in short-term and long-term outcomes after falls and MVAs, the leading TBI causes, which are not explained by confounders such as age. Findings may not generalize beyond patients receiving inpatient rehabilitation for TBI.

Background and purpose: People after mild traumatic brain injury (mTBI) show persistent deficits in reactive balance. Cortical processes engaged during preparation and execution of balance reactions are reflected in distinct cortical activity signatures that can be measured with electroencephalography (EEG). The purpose of this study was to 1) compare preparatory cortical beta activity and evoked cortical N1 responses during balance recovery in people with mTBI and controls, and 2) explore relationships between preparatory and evoked cortical activity. Methods: Participants (age 21-35 years) with symptomatic mTBI (n=5, 27±13 days post-injury) and controls (n=5) completed the instrumented and modified push & release tests of reactive balance. Cortical activity was recorded using encephalography (EEG). Main outcome measures were 1) preparatory sensorimotor cortical beta-bust power and duration prior to balance perturbation onset (-1s – 0s), and 2) cortical N1 response amplitude and latency during the post-perturbation balance recovery (50-250ms). Results: People with mTBI exhibited lower preparatory beta-burst power compared to controls (p=0.044, g=1.18). During balance recovery, cortical N1 responses occurred earlier in people with mTBI compared to controls (p=0.045, g=3.28). Relationships between preparatory and evoked cortical activity were altered after mTBI compared to controls; people after mTBI with greater beta-burst power and longer duration elicited shorter N1 latencies (r’s>−0.77, p’s<0.010). Discussion and conclusion: The results serve as preliminary, hypothesis-generating observations to guide future research directions investigating neural signatures of reactive balance deficits in people after mTBI. The preparatory brain state before reactive balance recovery should be explored as a potential target for post-mTBI balance rehabilitation.

Walking is an attentionally demanding process that draws from a limited pool of attentional resources. Dual-task assessments, where individuals perform a cognitive task while walking, often reveal changes in gait and balance due to competing attentional demands. As cognitive task difficulty increases, the attentional resources necessary to complete the task also increase, leading to greater interference with gait and balance. However, these interactions are typically examined using contrived lab-based tasks, leaving it unclear how the cognitive processes engaged during real-world movement impact walking. In the present study, we investigated whether increasing the attentional demand of spatial navigation, a cognitive process intrinsically linked to movement, interferes with gait and balance. Healthy adults completed an ambulatory virtual reality homing task in which they walked through a virtual environment and navigated to previously visited locations while wearing ankle and lumbar trackers. We increased the attentional demand of navigation by removing sensory cues during this homing phase: full cues, visual cues only, or self-motion cues only. Navigation performance declined as sensory cues were removed, but we observed no corresponding changes in their spatiotemporal gait and balance metrics. These results show that, in healthy adults, increasing the attentional demand of spatial navigation does not interfere with gait and balance during real-world movement. This finding suggests that locomotor control may be robust to navigation-related cognitive demands. Further research is needed to determine why navigation did not interfere with mobility and to clarify the relationship between these two interconnected processes.

Background: Rehabilitation of persistent imbalance in people with mild traumatic brain injury (mTBI) is challenging, and responsiveness to rehabilitation is often suboptimal. One reason for suboptimal outcomes may be patient heterogeneity within rehabilitation referrals. Specifically, people with greater vestibular and/or ocular-motor (V/O) symptoms may respond better to vestibular rehabilitation therapy (VRT) compared to those with greater mood or cognition symptoms. Poor performance of exercises may also explain suboptimal outcomes. This study aims to 1) assess if a wearable sensor-based multidimensional biofeedback system could enhance rehabilitation, 2) examine responsiveness to rehabilitation depending on the severity of V/O deficits, 3) characterize the impact of V/O deficits on gait and turning during seven days of unsupervised daily living and establish normative mobility data from active-duty service members. Methods: This study is a single-blinded randomized controlled trial involving 100 individuals experiencing persistent symptoms from subacute and chronic mTBI. Participants will be randomized into VRT with or without sensor-based biofeedback. Both groups will receive a 6-week VRT. All participants will be tested for balance, gait, turning, and V/O performance before and after VRT. We will compare the efficacy of VRT with or without biofeedback, stratified by the severity of V/O symptoms. Additionally, a subset of 50 participants with mTBI and 40 healthy active-duty service members will wear inertial sensors for seven days to quantify daily mobility. We will use the data to examine if the severity of V/O deficits following mTBI impacts daily mobility and to establish normative data for daily living mobility from military service members. Discussion: This study will be the first clinical trial to investigate whether wearable technology can improve rehabilitation outcomes for those with V/O symptoms by providing real-time biofeedback during rehabilitation. This work will also help to identify individuals with sensorimotor deficits associated with V/O subtypes. These results will enhance the assessment and rehabilitative care following mTBI by integrating objective measures to identify and address V/O subtypes. Furthermore, establishing normative data for daily living mobility from service members will aid in return-to-duty decision making following mTBI. Trial registration: This protocol is registered on ClinicalTrials.gov under the number NCT06381674. Registered on April 04, 2024. Recruited period from June 2024 to September 2028. https://clinicaltrials.gov/study/NCT06381674 . Trial Protocol v1 (Dated November 14, 2023)

Background: Mild traumatic brain injury (mTBI) can lead to persistent balance impairments, affecting daily functioning. While mTBI deficits in static and dynamic balance are well-documented, reactive balance—essential for recovering from perturbations—remains understudied, and the relationship with symptom severity and quality of life remains unclear. Objective: Examine reactive balance across different stages of mTBI recovery and its association with self-reported symptoms and quality of life. Methods: This cross-sectional study included 82 participants: 19 with acute (4-14 days post-injury), 11 with sub-acute (3-12 weeks post-injury), 11 with chronic (>12 weeks post-injury) mTBI, and 41 healthy controls. Reactive balance was assessed using the Instrumented-modified Push and Release under both single and cognitive dual-task conditions, measuring time to stability and step latency. Results: Participants with acute mTBI had longer step latencies ( P = .004 single-task; P = .016 dual-task) but no differences in time to stability compared to controls, while people with chronic mTBI exhibited longer time to stability ( P = .004 single-task; P = .017 dual-task) but no difference in step latencies compared to controls. Dizziness and total symptom severity were moderately associated with single- and dual-task time to stability and dual-task step latency acutely, and with single-task time to stability and dual-task step latency in the sub-acute phase. Conclusions: Reactive balance deficits persist chronically after mTBI and differ between people with acute, sub-acute, and chronic symptoms. These differences suggest people with chronic symptoms may prioritize different aspects of balance control compared to the people in the acute stage of recovery related to functional adaptations to self-reported symptoms.