Differential Sensitivity Between a Virtual Reality Balance Module and Clinically Used Concussion Balance Modalities

Balance assessments are part of the recommended clinical concussion evaluation, along with computerized neuropsychological testing and self-reported symptoms checklists. New technology has allowed for the creation of virtual reality (VR) balance assessments to be used in concussion care, but there is little information on the sensitivity and specificity of these evaluations. The purpose of this study is to establish the sensitivity and specificity of a VR balance module for detecting lingering balance deficits clinical concussion care

Brain structure can mediate or moderate the relationship of behavior to brain function and transcriptome. A preliminary study

Abnormalities in motor-control behavior, which have been with concussion and head acceleration events (HAE), can be quantified using virtual reality (VR) technologies. Motor-control behavior has been consistently mapped to the brain's somatomotor network (SM) using both structural (sMRI) and functional MRI (fMRI). However, no studies habe integrated HAE, motor-control behavior, sMRI and fMRI measures. Here, brain networks important for motor-control were hypothesized to show changes in tractography-based diffusion weighted imaging [difference in fractional anisotropy (dFA)] and resting-state fMRI (rs-fMRI) measures in collegiate American football players across the season, and that these measures would relate to VR-based motor-control. We firther tested if nine inflammation-related miRNAs were associated with behavior-structure-function variables. Using permutation-based mediation and moderation methods, we found that across-season dFA from the SM structural connectome (SM-dFA) mediated the relationship between across-season VR-based Sensory-motor Reactivity (dSR) and rs-fMRI SM fingerprint similarity (p = 0.007 and Teff = 47%). The interaction between dSR and SM-dFA also predicted (pF = 0.036, pbeta3 = 0.058) across-season levels of dmiRNA-30d through permutation-based moderation analysis. These results suggest (1) that motor-control is in a feedback relationship with brain structure and function, (2) behavior-structure-function can be connected to HAE, and (3) behavior-structure might predict molecular biology measures.Comment: 62 pages, 4 figures, 2 table

Dynamic strategies of human postural control

The two goals pursued in this study were to identify controllable dynamic characteristics of human posture and to approach the description of these characteristics by means of computer graphics. The notion that virtual time-to-contact, which specifies the spatio-temporal proximity of the pressure center to the stability boundary is one of the controllable parameters for postural dynamics, was examined while subjects performed a variety of upright postural movements where the speed, instructions and the base of support dimensions were experimentally manipulated. The rational for the new concept of virtual time-to-contact as well as a method for its computation and visualization with respect to two-dimensional stability boundary were elaborated.It was shown that the dynamic strategy of postural control defined by the interactive effects of environmental and task constraints channels a search for controllable parameters in relation to the organism-environment interaction. It appeared that range of postural movements, in terms of both whole body linear and angular kinematics and the center of pressure motion, is varied as a function of speed, physical dimension of the base of support and instruction, specifying additional constraints on postural dynamics. It was suggested that changes in task, experimental instruction and physical dimension of the base of support force the subjects to search for appropriate dynamic strategies in order to accommodate these task demands.Virtual time-to-contact values and associated variables were obtained and discussed in this study in terms of the mechanism of postural control including the processes by which performers explore their operational workspace. It was shown that virtual time-to-contact appeared to be specifically sensitive to changes in task, instructional constraints, physical dimension of the base of support, movement type and change in movement direction. Therefore, virtual time-to-contact can be considered as a unique perception-action mechanism which serves as an organizing principle for postural dynamics. It seems reasonable to suggest that additional sources of informational constraints such as vision availability, manipulations of physical base of support and so forth would be the appropriate experimental designs to further explore the dynamical properties of virtual time-to-contact.U of I OnlyETDs are only available to UIUC Users without author permissio

Virtual time-to-contact of postural stability boundaries as a function of support surface compliance

This study investigated the hypothesis that virtual time-to-contact, which specifies the time to reach the functional stability boundary, is a variable controlled in the maintenance of upright posture. Three different levels of support surface compliance were used on a force platform (no foam, 5 cm of foam, and 15 cm of foam). The participant’s task was to stand still under each surface support condition both with and without vision. The stability boundary was determined for each set of conditions where the participant was required to lean as far as possible in all directions of the horizontal plane without losing stability. The results showed that the no vision conditions had a significantly larger center of pressure displacement than the vision conditions. No vision and increasing support surface compliance also increased the velocity of the center of pressure trajectory. The distribution of the radial displacement of the center of pressure showed relatively equal frequency over spatial location with no central tendency. The virtual time-to-contact with the stability boundary decreased as platform surface support became more compliant. Furthermore, the distribution of virtual time over the effective scaling range was a power law with a larger exponent in the more unstable no vision and increasing surface foam conditions. The findings provide additional evidence for the hypothesis that virtual time-to-contact with stability boundaries is a postural control variable that is regulated rather than the preservation of minimal motion around the center of the stability region as proposed in pendulum models of posture

Postural Instability Detection: Aging and the Complexity of Spatial-Temporal Distributional Patterns for Virtually Contacting the Stability Boundary in Human Stance

<div><p>Falls among the older population can severely restrict their functional mobility and even cause death. Therefore, it is crucial to understand the mechanisms and conditions that cause falls, for which it is important to develop a predictive model of falls. One critical quantity for postural instability detection and prediction is the instantaneous stability of quiet upright stance based on motion data. However, well-established measures in the field of motor control that quantify overall postural stability using center-of-pressure (COP) or center-of-mass (COM) fluctuations are inadequate predictors of instantaneous stability. For this reason, 2D COP/COM virtual-time-to-contact (VTC) is investigated to detect the postural stability deficits of healthy older people compared to young adults. VTC predicts the temporal safety margin to the functional stability boundary ( =  limits of the region of feasible COP or COM displacement) and, therefore, provides an index of the risk of losing postural stability. The spatial directions with increased instability were also determined using quantities of VTC that have not previously been considered. Further, Lempel-Ziv-Complexity (LZC), a measure suitable for on-line monitoring of stability/instability, was applied to explore the temporal structure or complexity of VTC and the predictability of future postural instability based on previous behavior. These features were examined as a function of age, vision and different load weighting on the legs. The primary findings showed that for old adults the stability boundary was contracted and VTC reduced. Furthermore, the complexity decreased with aging and the direction with highest postural instability also changed in aging compared to the young adults. The findings reveal the sensitivity of the time dependent properties of 2D VTC to the detection of postural instability in aging, availability of visual information and postural stance and potential applicability as a predictive model of postural instability during upright stance.</p></div

In the upper left panel the 2D COP path of one single representative trial with normal vision, the respective polygon representation of the 2D functional stability boundary and two virtual COP trajectories at arbitrary time instants are illustrated in original aspect ratio, resolved in the force platform coordinate system.

<p>Each boundary segment represented one specific direction in relation to the COP (e.g. front or back segments). Additional representative 2D traces of the COP with the functional stability boundary as a function of age and loading (with normal vision) are also illustrated.</p