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Abstract of the Week

November Topic:

No 540: November 18, 2020

Integrated linear and nonlinear trunk dynamics identify residual concussion deficits

Bonnette S, Diekfuss JA, Grooms D, Myer GD, Meehan WP 3rd, Howell DR. Integrated linear and nonlinear trunk dynamics identify residual concussion deficits. Neurosci Lett. 2020 Jun 11;729:134975. doi: 10.1016/j.neulet.2020.134975. Epub 2020 Apr 13.
Postural sway is significantly affected by a mild traumatic brain injury, or concussion, and myriad methods have been developed to quantify the severity of concussion symptoms. The current manuscript quantifies postural sway-as measured by an inertial sensor-in youth athletes with concussion (n = 43, age = 14.4 ± 2.3 years, 56% female, tested median 7 days post-concussion) and healthy controls (n = 38, age = 14.9 ± 2.0 years, 55% female) during single-task and dual-task postural sway. A nonlinear analysis (i.e., recurrence quantification analysis [RQA]) and several common linear measures were used to quantify postural sway. Respectively, the two complementary types of analyses describe the structure and magnitude of postural sway. We hypothesized that participants who recently experienced a concussion would display differing postural sway dynamics (i.e., different in structure and magnitude) than control participants who had not experienced a concussion. Additionally, a logistic regression was performed to determine which combination of variables (nonlinear and linear) and task (single and dual) would best differentiate concussion and control participants. Significant differences between concussion and control participants were found in percent determinism, laminarity, and standard deviation of postural sway acceleration in both the single and the dual task. In the single task alone, mean diagonal line length and trapping time were additionally significantly different between groups. Moreover, the logistic regression model revealed that a mixture of linear and nonlinear measures across both single and dual tasks best classified concussed and non-concussed participants. Additionally, history of concussion was found to be a significant covariate in the model. These results extend past observations by demonstrating that a combination of posture sway tasks and measurements best differentiate participants with a concussion. These results highlight the need for future studies to replicate the findings in different populations and further determine which combinations of postural sway tasks and measurements best classify participants with concussions.
PMID: 32298725
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No 540: November 5, 2020
Youth With Concussion Have Less Adaptable Gait Patterns Than Their Uninjured Peers: Implications for Concussion Management
Howell DR, Bonnette S, Diekfuss JA, Grooms DR, Myer GD, Meehan WP 3rd. Youth With Concussion Have Less Adaptable Gait Patterns Than Their Uninjured Peers: Implications for Concussion Management. J Orthop Sports Phys Ther. 2020 Aug;50(8):438-446. doi: 10.2519/jospt.2020.9133. Epub 2020 May 22. 32441192.
Objective: To compare cross-recurrence quantification analysis measurements obtained during gait between adolescents who sustained a diagnosed concussion within 14 days of assessment and healthy adolescents.
Design: Cross-sectional study.
Methods: Youth athletes with concussion (n = 43; mean ± SD age, 14.4 ± 2.3 years; 56% female; tested median, 7 days post concussion) and healthy controls (n = 38; age, 14.9 ± 2.0 years; 55% female) completed a single-task and dual-task gait protocol while wearing a set of inertial sensors. We used cross-recurrence quantification analysis techniques to quantify the similarity between accelerations obtained from the sensor on the dorsum of each foot. Four outcome variables were compared between groups: percent determinism, average diagonal-line length, laminarity, and trapping time.
Results: Athletes with concussion had significantly higher percent determinism, laminarity, and trapping time than the control group in single-task and dual-task conditions (P<.05). Gait patterns, when simultaneously completing a secondary cognitive task (dual task), were no different from gait patterns under a single-task condition.
Conclusion: Higher percent determinism, laminarity, and trapping time among athletes with concussion suggest that concussion may be associated with a more stuck and predictable gait pattern. These altered movement patterns may be one reason for underlying slower gait speeds that have been observed following concussion.
PMID: 32441192
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October Topic: Gait

No 539: October 28, 2020

Development of a Computerized Device for Evaluating Vestibular Function in Locomotion: A New Evaluation Tool of Vestibular Hypofunction

Chen PY, Chou LW, Jheng YC, et al. Development of a Computerized Device for Evaluating Vestibular Function in Locomotion: A New Evaluation Tool of Vestibular Hypofunction. Front Neurol. 2020;11:485. Published 2020 Jun 12. doi:10.3389/fneur.2020.00485
To evaluate vestibular function in the clinic, current assessments are applied under static conditions, such as with the subject in a sitting or supine position. Considering the complexities of daily activities, the combination of dynamic activities, dynamic visual acuity (DVA) and postural control could produce an evaluation that better reflects vestibular function in daily activities.
Objective: To develop a novel sensor-based system to investigate DVA, walking trajectory, head and trunk movements and the chest-pelvis rotation ratio during forward and backward overground walking in both healthy individuals and patients with vestibular hypofunction.
Methods: Fifteen healthy subjects and 7 patients with bilateral vestibular hypofunction (BVH) were recruited for this study. Inertial measurement units were placed on each subject's head and torso. Each subject walked forward and backward for 5 m twice with 2 Hz head yaw. Our experiment comprised 2 stages. In stage 1, we measured forward (FW), backward (BW), and medial-lateral (MLW) walking trajectories; head and trunk movements; and the chest-pelvis rotation ratio. In stage 2, we measured standing and locomotion DVA (loDVA). Using Mann–Whitney U-test, we compared the abovementioned parameters between the 2 groups.
Results: Patients exhibited an in-phase chest/pelvis reciprocal rotation ratio only in FW. The walking trajectory deviation, calculated by normalizing the summation of medial-lateral swaying with 1/2 body height (%), was significantly larger (FW mean ± standard deviation: 20.4 ± 7.1% (median (M)/interquartile range (IQR): 19.3/14.4–25.2)in healthy vs. 43.9 ± 27. 3% (M/IQR: 36.9/21.3–56.9) in patients, p = 0.020)/(BW mean ± standard deviation: 19.2 ± 11.5% (M/IQR: 13.6/10.4–25.3) in healthy vs. 29.3 ± 6.4% (M/IQR: 27.7/26.5–34.4) in patients, p = 0.026), and the walking DVA was also significantly higher (LogMAR score in the patient group [FW LogMAR: rightDVA: mean ± standard deviation:0.127 ± 0.081 (M/IQR: 0.127/0.036–0.159) in healthy vs. 0.243 ± 0.101 (M/IQR: 0.247/0.143–0.337) in patients (p = 0.013) and leftDVA: 0.136 ± 0.096 (M/IQR: 0.127/0.036–0.176) in healthy vs. 0.258 ± 0.092 (M/IQR: 0.247/0.176–0.301) in patients (p = 0.016); BW LogMAR: rightDVA: mean ± standard deviation: 0.162 ± 0.097 (M/IQR: 0.159/0.097–0.273) in healthy vs. 0.281 ± 0.130 (M/IQR: 0.273/0.176–0.418) in patients(p = 0.047) and leftDVA: 0.156 ± 0.101 (M/IQR: 0.159/0.097–0.198) in healthy vs. 0.298 ± 0.153 (M/IQR: 0.2730/0.159–0.484) in patients (p = 0.038)].
Conclusions: Our sensor-based vestibular evaluation system provided a more functionally relevant assessment for the identification of BVH patients.
PMID: 32595589
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No 538: October 21, 2020

Selective suppression of the vestibulo-ocular reflex during human locomotion

Dietrich H, Wuehr M. Selective suppression of the vestibulo-ocular reflex during human locomotion. J Neurol. 2019 Sep;266(Suppl 1):101-107. doi: 10.1007/s00415-019-09352-7. Epub 2019 May 9
Introduction: In lower vertebrates, gaze stabilization during locomotion is at least partially driven by a direct coupling of spinal locomotor commands with extraocular motor signals. To what extent locomotor feed-forward mechanisms contribute to gaze stabilization during human locomotion is yet unknown. In principle, the feasibility of a feed-forward regulation of gaze during locomotion should critically depend on the spatiotemporal coupling between body and head kinematics and hence the internal predictability of head movements (HMP). The present study thus investigated whether changes in eye-head coordination during human locomotion can be explained by concurrent changes in HMP.
Methods: Eye and head movements were recorded at different locomotor speeds in light and darkness to obtain the gain and phase of the horizontal and vertical angular VOR (aVOR). Potential correlations between aVOR performance and HMP were analyzed in dependence of locomotor speed and gait cycle phase.
Results: Horizontal aVOR responses persisted independent of locomotor speed. In contrast, with increasing locomotor speed vertical eye-head coordination switched from a VOR-driven compensatory mode to a synergistic behavior where head and eyes move in phase. Concurrently, vertical HMP increased with faster locomotion. Furthermore, modulations in vertical aVOR gain across the gait cycle corresponded to simultaneous alterations in vertical HMP.
Conclusion: The vertical aVOR appears to be suppressed during faster walking and running, whereas at the same time, the predictability of resultant head movements increases. This suggests that during stereotyped human locomotion, internal feed-forward commands supplement or even suppress sensory feedback to mediate gaze stabilization in the vertical plane.
PMID: 31073715
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No 537: October 14, 2020

Strategies for Gaze Stabilization Critically Depend on Locomotor Speed

Dietrich H, Wuehr M. Strategies for Gaze Stabilization Critically Depend on Locomotor Speed. Neuroscience. 2019 Jun 1;408:418-429. doi: 10.1016/j.neuroscience.2019.01.025. Epub 2019 Jan 29. 
Locomotion involves complex combinations of translational and rotational head movements. For gaze stability, this necessitates the interplay of angular and linear vestibulo-ocular reflexes (VOR) as well as the integration of visual feedback about the desired viewing distance. Furthermore, gaze stabilizing systems must be able to cope with vast differences in head motion brought about by changing locomotor speeds and patterns (walking vs. running). The present study investigated horizontal and vertical angular VOR (aVOR) and linear gaze stabilization (lGS) as well as compensation for linear head movements by angular counter rotation of the head during treadmill walking and running at different velocities (0.4 to 2.4 m/s) while fixating either a close (0.5 m) or distant (2.0 m) target. In the horizontal plane, the aVOR predominated throughout all locomotor speeds, whereas the compensation of linear translations was highly variable and generally insufficient. In contrast, in the vertical plane, eye and angular head motion steadily became more in phase with increasing locomotor speed, which served to optimize linear motion compensation. Furthermore, the timing of the vertical aVOR became more automated and independent of visual feedback during faster locomotion. Thus, horizontal and vertical gaze stabilization strategies appear to be considerably different. Whereas horizontal gaze control is likely governed by passive sensorimotor reflexes throughout all locomotor speeds, vertical gaze stabilization switches to an automated feed-forward control at faster locomotion. This switch is presumably driven by efference copies from spinal locomotor commands that were previously shown to govern gaze stabilization in animal models during stereotypic locomotion.
PMID: 30703510
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