Influence of virtual height exposure on postural reactions to support surface translations

Cleworth, Taylor W.; Chua, Romeo; Inglis, James; Carpenter, Mark G.

doi:10.1016/j.gaitpost.2016.04.006

Cited by 44 publications

(45 citation statements)

References 29 publications

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“…Increases in muscle spindle sensitivity (as suggested in the present study), in conjunction with increased vestibular gain (Horslen et al ., ; Naranjo et al ., , ; Lim et al ., ) and altered Ib reflexes (Horslen et al ., ), might contribute to larger balance‐correcting responses to postural perturbations, as typically observed with increased postural threat (Brown and Frank, ; Carpenter et al ., ; Cleworth et al . ), which are considered to involve supraspinal pathways (Horak and Macpherson, ). Similarly, increased muscle spindle sensitivity would enable people to maintain, or increase, the volume of muscle spindle afferent feedback despite reducing actual sway with threat.…”

Section: Discussionmentioning

confidence: 99%

Increased human stretch reflex dynamic sensitivity with height‐induced postural threat

Horslen

Zaback

Inglis

et al. 2018

The Journal of Physiology

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Postural threat increases soleus tendon-tap (t-) reflexes. However, it is not known whether t-reflex changes are a result of central modulation, altered muscle spindle dynamic sensitivity or combined spindle static and dynamic sensitization. Ramp-and-hold dorsiflexion stretches of varying velocities and amplitudes were used to examine velocity- and amplitude-dependent scaling of short- (SLR) and medium-latency (MLR) stretch reflexes as an indirect indicator of spindle sensitivity. t-reflexes were also performed to replicate previous work. In the present study, we examined the effects of postural threat on SLR, MLR and t-reflex amplitude, as well as SLR-stretch velocity scaling. Forty young-healthy adults stood with one foot on a servo-controlled tilting platform and the other on a stable surface. The platform was positioned on a hydraulic lift. Threat was manipulated by having participants stand in low (height 1.1 m; away from edge) then high (height 3.5 m; at the edge) threat conditions. Soleus stretch reflexes were recorded with surface electromyography and SLRs and MLRs were probed with fixed-amplitude variable-velocity stretches. t-reflexes were evoked with Achilles tendon taps using a linear motor. SLR, MLR and t-reflexes were 11%, 9.5% and 16.9% larger, respectively, in the high compared to low threat condition. In 22 out of 40 participants, SLR amplitude was correlated to stretch velocity at both threat levels. In these participants, the gain of the SLR-velocity relationship was increased by 36.1% with high postural threat. These findings provide new supportive evidence for increased muscle spindle dynamic sensitivity with postural threat and provide further support for the context-dependent modulation of human somatosensory pathways.

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Section: Discussionmentioning

confidence: 99%

Increased human stretch reflex dynamic sensitivity with height‐induced postural threat

Horslen

Zaback

Inglis

et al. 2018

The Journal of Physiology

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“…Since these initial studies, physically raising the height of the support surface on which individuals stand has been used extensively to: (1) confirm the effects on standing balance control in young and older healthy adults ( 22 – 36 ), and patient populations such as individuals with unilateral vestibular loss ( 37 ) and Parkinson's disease ( 38 , 39 ); (2) extend the effects of threat on different types of postural tasks including anticipatory postural control ( 34 , 40 – 42 ), reactive postural control ( 43 , 44 ), functional balance tasks [e.g., one leg stance; ( 28 )], and normal and adaptive gait ( 45 – 53 ); and (3) explore the neural mechanisms underlying these threat effects ( 44 , 54 – 67 ). Studies have also provided converging evidence to confirm that the threat of standing on elevated surfaces (i.e., real or virtual) can evoke psychological (e.g., self-reported increases in perceived anxiety and fear) and physiological responses (e.g., increases in electrodermal activity, blood pressure) typically observed in fearful or anxious conditions [e.g., ( 25 , 28 – 30 , 32 , 34 , 35 , 40 )].…”

Section: Introductionmentioning

confidence: 99%

New Insights on Emotional Contributions to Human Postural Control

Adkin

Carpenter

2018

Front. Neurol.

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It has been just over 20 years since the effects of height-induced threat on human postural control were first investigated. Raising the height of the support surface on which individuals stood increased the perceived consequences of instability and generated postural control changes. Since this initial work, converging evidence has accumulated supporting the efficacy of using height-induced threat to study the effects of emotions on postural control and confirming a direct influence of threat-related changes in arousal, anxiety, and fear of falling on all aspects of postural control, including standing, anticipatory, and reactive balance. In general, threat-related postural changes promote a greater physical safety margin while maintaining upright stance. We use the static balance literature to critically examine the current state of knowledge regarding: (1) the extent to which threat-related changes in postural control are sensitive to threat-related changes in emotions; (2) the underlying neurophysiological and cognitive mechanisms that may contribute to explaining the relationship between emotions and postural control; and (3) the generalizability of threat-related changes across different populations and types of threat. These findings have important implications for understanding the neuromechanisms that control healthy balance, and highlight the need to recognize the potential contributions of psychological and physiological factors to balance deficits associated with age or pathology. We conclude with a discussion of the practical significance of this research, its impact on improving diagnosis and treatment of postural control deficits, and potential directions for future research.

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“…Another point of view is that the delayed reaction of our AD patients when facing the visual-vestibulosomatosensory conflict posed by the VR paradigm could also be due to impairments of visual motion, shape [ 53 ], and depth perception [ 54 ] reported in AD. Furthermore, threat-related factors influence the neuromechanical postural responses to an unpredictable perturbation, and these responses may be facilitated in younger healthy adults [ 55 ]. Thus, the emotional state, such fear of and anxiety about falling, may explain different CPA responses among AD patients, in particular in AD fallers.…”

Section: Discussionmentioning

confidence: 99%

Compensatory Postural Adjustments in an Oculus Virtual Reality Environment and the Risk of Falling in Alzheimer's Disease

Gago

Yelshyna²,

Bicho³

et al. 2016

Dement Geriatr Cogn Disord Extra

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Background/Aims: Alzheimer's disease (AD) patients have an impaired ability to quickly reweight central sensory dependence in response to unexpected body perturbations. Herein, we aim to study provoked compensatory postural adjustments (CPAs) in a conflicting sensory paradigm with unpredictable visual displacements using virtual reality goggles. Methods: We used kinematic time-frequency analyses of two frequency bands: a low-frequency band (LB; 0.3-1.5 Hz; mechanical strategy) and a high-frequency band (HB; 1.5-3.5 Hz; cognitive strategy). We enrolled 19 healthy subjects (controls) and 21 AD patients, divided according to their previous history of falls. Results: The AD faller group presented higher-power LB CPAs, reflecting their worse inherent postural stability. The AD patients had a time lag in their HB CPA reaction. Conclusion: The slower reaction by CPA in AD may be a reflection of different cognitive resources including body schema self-perception, visual motion, depth perception, or a different state of fear and/or anxiety.

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Influence of virtual height exposure on postural reactions to support surface translations

Cited by 44 publications

References 29 publications

Increased human stretch reflex dynamic sensitivity with height‐induced postural threat

Increased human stretch reflex dynamic sensitivity with height‐induced postural threat

New Insights on Emotional Contributions to Human Postural Control

Compensatory Postural Adjustments in an Oculus Virtual Reality Environment and the Risk of Falling in Alzheimer's Disease

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