Anteroposterior and mediolateral postural adaptations during single and duals tasks in healthy young adults

Dual tasks are fundamental and standard for daily walking and balance movements. However, further research is required to determine the comprehensive postural profile during challenging dual cognitive tasks. To distinguish the influence of dual cognitive tasks on anterior-posterior (AP) and mediolateral (ML) jerk (direction of sway), velocity, and distance in young adults with normal balance systems. Nineteen subjects took part in this inquiry (2 males and 17 females), with a mean age of 23.9+\- 2.3 years. The participants were instrumented using a lumbar accelerometer and a dynamometer designed to capture sway. All subjects completed eight balance tests comprising four single and four dual-cognitive tasks involving counting backward by three, starting at the number 100 (dual-task). Postural modifications were prominent in the AP direction, with a faster jerk, velocity, and considerable distance than in the ML direction. The introduction to challenging balance situations, including dual tasks, provoke AP direction adaptations to preserve balance through variations in AP parameters, indicating the engagement of the sensory reweighting system.

The Effects of Exergaming on Sensory Reweighting and Mediolateral Stability of Women Aged Over 60: Usability Study (Preprint)

BACKGROUND Older adults tend to experience difficulties in switching quickly between various reliable sensory inputs, which ultimately may contribute to an increased risk of falls and injuries. Sideward falls are the most frequent cause of hip fractures among older adults. Recently, exergame programs have been confirmed as beneficial tools for enhancing postural control, which can reduce the risk of falls. However, studies to explore more precisely which mechanism of exergaming directly influences older women’s ability to balance are still needed. OBJECTIVE Our aim was to evaluate, in a single-group pretest/posttest/follow-up usability study, whether Kinect exergame balance training might have a beneficial impact on the sensory reweighting in women aged over 60. METHODS A total of 14 healthy women (mean age 69.57 [SD 4.66] years, mean body mass index 26.21 [SD 2.6] kg/m²) participated in the study. The volunteers trained with the commercially available games of Kinect for Xbox 360 console 3 times (30 minutes/session) a week over a 6-week period (total of 18 visits). Participants’ postural sway in both the anteroposterior (AP) and mediolateral (ML) directions was recorded with NeuroCom Balance Master 6.0. To assess and measure postural sensory reweighting, the Modified Clinical Test of Sensory Interaction in Balance was used, where volunteers were exposed to various changes in visual (eyes open or eyes closed) and surface conditions (firm or foam surface). RESULTS In the ML direction, the Kinect exergame training caused a significant decrease in the sway path on the firm surface with the eyes open (<i>P</i>&lt;.001) and eyes closed (<i>P</i>=.001), and on the foam surface with the eyes open (<i>P</i>=.001) and eyes closed (<i>P</i>&lt;.001) conditions compared with baseline data. The follow-up measurements when compared with the baseline data showed a significant change in the sway path on the firm surface with the eyes open (<i>P</i>&lt;.001) and eyes closed (<i>P</i>&lt;.001) conditions, as well as on the foam surface with the eyes open (<i>P</i>=.003) and eyes closed (<i>P</i>&lt;.001) conditions. Besides, on the firm surface, there were no significant differences in sway path values in the AP direction between the baseline and the posttraining measurements (eyes open: <i>P</i>=.49; eyes closed: <i>P</i>=.18). Likewise, on the foam surface, there were no significant differences in sway path values in the AP direction under both eyes open (<i>P</i>=.24) and eyes closed (<i>P</i>=.84) conditions. CONCLUSIONS The improved posturography measurements of the sway path in the ML direction might suggest that the Kinect exergame balance training may have effects on sensory reweighting, and thus on the balance of women aged over 60. Based on these results, Kinect exergaming may provide a safe and potentially useful tool for improving postural stability in the crucial ML direction, and thus it may help reduce the risk of falling.

Visual-vestibular mismatch correlates with headache

BACKGROUND: Dizziness affects 20–30%of the general population. A subgroup of dizzy patients with chronic migraine suffers vertigo implying that the migraine has a vestibular component. Vestibular migraine remains a diagnosis of exclusion based on history. OBJECTIVE: A link between headaches and dizziness suggests that these individuals would demonstrate dizziness and instability in complex, dynamic visual environments as a result of an inability to correctly process conflicting visual and vestibular signals. METHODS: A convenience sample of 74 patients (22 men and 52 women; average age 56.2 years) who presented with complaints of dizziness participated. Effects of Visual-Vestibular Mismatch (VVM) were measured using a modified VVM questionnaire. Visual dependence was measured as the error to subjective visual vertical using a computerized Rod and Frame test. RESULTS: Forty-two participants (56.8%) tested positive for VVM. Of these, 68.9%were patients with concomitant complaints of headaches. Visual dependence was present in 41.5%of all patients but showed no significant correlation with headache. 22.2%of patients had visual dependence and complained of headaches. CONCLUSIONS: These results demonstrate that sensory reweighting occurs in patients experiencing dizziness and headache, supports the role of vestibular involvement in this disorder, and provides future direction for novel interventions.

Persistent visual and vestibular impairments for Postural control following concussion

ObjectiveThe purpose of this study was to examine sensory reweighting for upright stance in three groups (i.e., sub-acute concussion, concussion history, control).BackgroundBalance impairments are common following concussion; however, the physiologic mechanisms underlying these impairments are not well understood.Design/methodsThere were 13 participants (8 women, 21 ± 3 years) between 2 weeks and 6 months post-injury who reported being asymptomatic at the time of testing (i.e., sub-acute concussion group), 13 participants (8 women, 21 ± 1 year) with a history of concussion (i.e., concussion history group, >1 year following concussion), and 26 participants (8 women, 22 ± 3 years) with no concussion history (i.e., control group). We assessed sensory reweighting by simultaneously perturbing participants' visual, vestibular, and proprioceptive systems. The visual stimulus was a sinusoidal translation of the visual scene at 0.2Hz, the vestibular stimulus was ±1 mA binaural monopolar galvanic vestibular stimulation (GVS) at 0.36Hz, and the proprioceptive stimulus was Achilles' tendon vibration at 0.28Hz. The visual stimulus was presented at two different amplitudes (low vision = 0.2m, high vision = 0.8m). We computed center of mass gain to each modality.ResultsThe sub-acute concussion group (95% confidence interval = 0.078-0.115, p = 0.001) and the concussion history group (95% confidence interval = 0.056-0.094, p = 0.038) had higher gains to the visual stimulus than the control group (95% confidence interval = 0.040-0.066). The sub-acute concussion group (95% confidence interval = 0.795–1.159, p = 0.002) and the concussion history group (95% confidence interval = 0.633–1.012, p = 0.018) had higher gains to the vestibular stimulus than the control group (95% confidence interval = 0.494-0.752). There were no group differences in gains to the proprioceptive stimulus and there were no group differences in sensory reweighting.ConclusionsFollowing concussion, participants responded more strongly to visual and vestibular stimuli during upright stance, suggesting they may have abnormal dependence on visual and vestibular feedback. These findings may indicate an area for targeted rehabilitation interventions.

Microgravity Effects on the Human Brain and Behavior: Dysfunction and Adaptive Plasticity

Emerging plans for travel to Mars and other deep space destinations make it critical for us to understand how spaceflight affects the human brain and behavior. Research over the past decade has demonstrated two co-occurring patterns of spaceflight effects on the brain and behavior: dysfunction and adaptive plasticity. Evidence indicates the spaceflight environment induces adverse effects on the brain, including upward fluid shifts, gray matter changes, and white matter declines. Past work also suggests that the spaceflight environment induces adaptive neural effects such as sensory reweighting and neural compensation. Here, we introduce a new conceptual framework to synthesize spaceflight effects on the brain, Spaceflight Perturbation Adaptation Coupled with Dysfunction (SPACeD). We review the literature implicating neurobehavioral dysfunction and adaptation in response to spaceflight and microgravity analogues, and we consider pre-, during-, and post-flight factors that may interact with these processes. We draw several instructive parallels with the aging literature which also suggests co-occurring neurobehavioral dysfunction and adaptive processes. We close with recommendations for future spaceflight research, including: 1) increased efforts to distinguish between dysfunctional versus adaptive effects by testing brain--behavioral correlations, and 2) greater focus on tracking recovery time courses.