An Engineering Model to Test for Sensory Reweighting: Nonhuman Primates Serve as a Model for Human Postural Control and Vestibular Dysfunction (original) (raw)
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Postural compensation for vestibular loss and implications for rehabilitation
Restorative neurology and neuroscience, 2010
This chapter summarizes the role of the vestibular system in postural control so that specific and effective rehabilitation can be designed that facilitates compensation for loss of vestibular function. Patients with bilateral or unilateral loss of peripheral vestibular function are exposed to surface perturbations to quantify automatic postural responses. Studies also evaluated the effects of audio- and vibrotactile-biofeedback to improve stability in stance and gait. The most important role of vestibular information for postural control is to control orientation of the head and trunk in space with respect to gravitoinertial forces, particularly when balancing on unstable surfaces. Vestibular sensory references are particularly important for postural control at high frequencies and velocities of self-motion, to reduce trunk drift and variability, to provide an external reference frame for the trunk and head in space; and to uncouple coordination of the trunk from the legs and the h...
Postural Compensation for Vestibular Loss
Annals of the New York Academy of Sciences, 2009
To what extent can remaining sensory information and/or sensory biofeedback compensate for loss of vestibular information in controlling postural equilibrium? The primary role of the vestibulospinal system is as a vertical reference for control of the trunk in space, with increasing importance as the surface becomes increasingly unstable. Our studies with patients with bilateral loss of vestibular function show that vision or light touch from a fingertip can substitute as a reference for earth vertical to decrease variability of trunk sway when standing on an unstable surface. However, some patients with bilateral loss compensate better than others and we find that those with more complete loss of bilateral vestibular function compensate better than those with measurable vestibulo-ocular reflexes. In contrast, patients with unilateral vestibular loss who reweight sensory dependence to rely on their remaining unilateral vestibular function show better functional performance than those who do not increase vestibular weighting on an unstable surface. Light touch of <100 grams or auditory biofeedback can be added as a vestibular vertical reference to stabilize trunk sway during stance. Postural ataxia during tandem gait in patients with unilateral vestibular loss is also significantly improved with vibrotactile biofeedback to the trunk, beyond improvements due to practice. Vestibular rehabilitation should focus on decreasing hypermetria, decreasing an over-dependence on surface somatosensory inputs, increasing use of any remaining vestibular function, substituting or adding alternative sensory feedback related to trunk sway, and practicing challenging balance tasks on unstable surfaces.
Experimental Brain Research, 1998
Interactions between proprioceptive and vestibular inputs contributing to the generation of balance corrections may vary across muscles depending on the availability of sensory information at centres initiating and modulating muscle synergies, and the efficacy with which the muscle action can prevent a fall. Information which is not available from one sensory system may be obtained by switching to another. Alternatively, interactions between sensory systems and the muscle to which this interaction is targeted may be fixed during neural development and not switchable. To investigate these different concepts, balance corrections with three different sets of proprioceptive trigger signals were examined under eyesopen and eyes-closed conditions in the muscles of normal subjects and compared with those of subjects with bilateral peripheral vestibular loss. The different sets of early proprioceptive inputs were obtained by employing three combinations of support surface rotation and translation, for which ankle inputs were nulled, normal or enhanced,
Relationship between changes in vestibular sensory reweighting and postural control complexity
Experimental Brain Research, 2016
Complexity measures have become increasingly prominent in the postural control literature. Several studies have found associations between clinical balance improvements and complexity, but the relationship between sensory reweighting and complexity changes has remained unobserved. The purpose of this study was to determine the relationship between sensory reweighting via Wii Fit balance training and complexity. Twenty healthy adults completed 6 weeks of training. Participants completed the sensory organization test (SOT) before and after the sessions. Complexity of postural control was analyzed through sample entropy of the centerof-pressure velocity time series in the resultant, anterior-posterior (AP), and medial-lateral directions, and compared to SOT summary score changes. Significant differences were found between pre-and post-training for the condition five (p < .001, d = .525) and vestibular summary scores (p < .001, d = .611). Similarly, changes in complexity were observed from pre-to posttraining in the resultant (p = .040, d = .427) direction. While the AP velocity was not significant (p = .07, d = .355), its effect size was moderate. A moderate correlation was revealed in the posttest between AP complexity and condition 5 (r = .442, p = .05), as well as between AP complexity and the vestibular summary score (r = .351, p = .13). The results of this study show that a moderate relationship exists between postural control complexity and the vestibular system, suggesting that complexity may reflect the neurosensory organization used to maintain upright stance.
Characterizing sensory re-weighting for human postural control
2006
In order to survive in the wide range of sensory contexts that comprise our physical world, the nervous system employs adaptive mechanisms that optimize functional behaviors within a given sensory environment. Human bipedal stance control requires that the nervous system obtain relevant information about the environment and the body's relationship with it from multiple sensory systems. How does the nervous system accomplish this when the sensory environment compromises the information available from a given sensory system? In previous theoretical and empirical work, we have provided evidence of nonlinearities that are consistent with an hypothesis of sensory re-weighting: The nervous system adapts to changing sensory contexts by decreasing its dependence, or weighting, on the compromised system and increases its weighting of other inputs. This thesis presents empirical findings that further support the sensory re-weighting hypothesis and further efforts towards characterizing sensory re-weighting by providing empirical results that provide important constraints on any proposed sensory re-weighting scheme.
Acta physiologica et pharmacologica Bulgarica, 2001
We investigated which sensor had dominant contribution to vestibulo-ocular reflex (VOR) and postural sway (PS) for the optimal body balance maintenance under conditions of visual or/and somatosensory input reduction. Healthy subjects were examined in upright stance on stable platform and foam rubber, under following conditions: in quiet stance with eyes open (EO) and closed (EC); during voluntary head movements in horizontal plane at frequency 0.2 - 0.3 Hz with EO (HO) and EC (HC). The results showed that PS increased smaller during HC than during HO on both supports stable and unstable, but particularly on the foam rubber. Mean gain of VOR induced by HO was 1.2 and this one evoked by HC was 0.9 on the two supports. Therefore, when in upright stance the vestibular input is stimulated, the reduction of either or both inputs visual and proprioceptive influences postural stability positively while VOR is affected negligibly. Hence, the vestibular contribution to both VOR and PS is domi...
The importance of sensory feedback for postural control in stance is evident from the balance improvements occurring when sensory information from the vestibular, somatosensory, and visual systems is available. However, the extent to which also audiobiofeedback (ABF) information can improve balance has not been determined. It is also unknown why additional artiWcial sensory feedback is more eVective for some subjects than others and in some environmental contexts than others. The aim of this study was to determine the relative eVectiveness of an ABF system to reduce postural sway in stance in healthy control subjects and in subjects with bilateral vestibular loss, under conditions of reduced vestibular, visual, and somatosensory inputs. This ABF system used a threshold region and non-linear scaling parameters customized for each individual, to provide subjects with pitch and volume coding of their body sway. ABF had the largest eVect on reducing the body sway of the subjects with bilateral vestibular loss when the environment provided limited visual and somatosensory information; it had the smallest eVect on reducing the sway of subjects with bilateral vestibular loss, when the environment provided full somatosensory information. The extent that all subjects substituted ABF information for their loss of sensory information was related to the extent that each subject was visually dependent or somatosensory-dependent for their postural control. Comparison of postural sway under a variety of sensory conditions suggests that patients with profound bilateral loss of vestibular function show larger than normal information redundancy among the remaining senses and ABF of trunk sway. The results support the hypothesis that the nervous system uses augmented sensory information diVerently depending both on the environment and on individual proclivities to rely on vestibular, somatosensory or visual information to control sway.
Vestibular training promotes adaptation of multisensory integration in postural control
Gait & Posture, 2019
Background: Postural stability depends on the integration of the multisensory system to produce motor outputs. When visual and somatosensory input is reliable, this reduces reliance on the vestibular system. Despite this, vestibular loss can still cause severe postural dysfunction. Training one or more of the three sensory systems through vestibular habituation and adaptation can alter sensory weighting and change postural behavior. Aim: The purpose of this study was to assess sensory reweighting of postural control processing after combined vestibular activation with voluntary weight shift training in healthy adults. Methods: Thirty-three healthy individuals (18-35 y.o.) were randomly assigned to one of three groups: No training (control), visual feedback weight shift training (WST) coupled with an active horizontal headshake (HS) activity to elicit a vestibular perturbation, or the same WST without HS (NoHS). Training was performed 2x/day, every other day (M, W, F), totaling six sessions. Pre-and post-assessments on the Sensory Organization Test (SOT) were performed. Separate between-and within-repeated measures ANOVAs were used to analyze the six SOT equilibrium scores, composite scores, sensory ratios and center of pressure (COP) variables by comparing baseline to post-training. Alpha level was set at p < .05. Results: There was a significant group x session x condition change (p = .012) in the COP multiscale entropy (MSE) velocity sway in the HS group during SOT conditions 5 and 6. Similarly, COP medio-lateral standard deviation sway (ML Std) showed group x session x visual condition (p = .028), due to HS in condition 6 relative to other two groups. Conclusion: Postural training can alter sensory organization after a visual feedback-vestibular activation training protocol, suggesting a possible sensory reweighting through vestibular adaptation and/or habituation. Significance: Translating these findings into a vestibular-impaired population can stimulate the design of a rehabilitation balance protocol.