Effects of visual motion consistent or inconsistent with gravity on postural sway

Balestrucci, Priscilla; Daprati, Elena; Lacquaniti, Francesco; Maffei, Vincenzo

doi:10.1007/s00221-017-4942-3

Cited by 26 publications

(24 citation statements)

References 71 publications

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“…In humans, brain regions compute the predicted effects of gravity by combining and comparing multiple sensory cues with an IMG (Lacquaniti et al, 2014;Balestrucci et al, 2017). The model explores the idea that locomotor adaptations, as those observed in our study, arise from an error signal generated by information from the visual-vestibular network incongruent with IMG predictions (Balestrucci et al, 2017). This mismatch may trigger the indirect prediction mechanisms, in which visual information predominates for a rapid, initial prediction and adjustment of gait pattern (O'Connor and Donelan, 2012).…”

Section: Neural Mechanismsmentioning

confidence: 86%

“…The predictive system is critically based on an internal model of gravity (IMG) that regulates locomotion in accord with estimates of physical laws of gravity. In humans, brain regions compute the predicted effects of gravity by combining and comparing multiple sensory cues with an IMG (Lacquaniti et al, 2014;Balestrucci et al, 2017). The model explores the idea that locomotor adaptations, as those observed in our study, arise from an error signal generated by information from the visual-vestibular network incongruent with IMG predictions (Balestrucci et al, 2017).…”

Section: Neural Mechanismsmentioning

confidence: 92%

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Seeing Gravity: Gait Adaptations to Visual and Physical Inclines – A Virtual Reality Study

et al. 2020

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Using advanced virtual reality technology, we demonstrate that exposure to virtual inclinations visually simulating inclined walking induces gait modulations in a manner consistent with expected gravitational forces (i.e., acting upon a free body), suggesting vision-based perception of gravity. The force of gravity critically impacts the regulation of our movements. However, how humans perceive and incorporate gravity into locomotion is not well understood. In this study, we introduce a novel paradigm for exposing humans to incongruent sensory information under conditions constrained by distinct gravitational effects, facilitating analysis of the consistency of human locomotion with expected gravitational forces. Young healthy adults walked under conditions of actual physical inclinations as well as virtual inclinations. We identify and describe 'braking' and 'exertion' effects-locomotor adaptations accommodating gravito-inertial forces associated with physical inclines. We show that purely visual cues (from virtual inclinations) induce consistent locomotor adaptations to counter expected gravitybased changes, consistent with indirect prediction mechanisms. Specifically, downhill visual cues activate the braking effect in anticipation of a gravitational boost, whereas uphill visual cues promote an exertion effect in anticipation of gravitational deceleration. Although participants initially rely upon vision to accommodate environmental changes, a sensory reweighting mechanism gradually reprioritizes body-based cues over visual ones. A high-level neural model outlines a putative pathway subserving the observed effects. Our findings may be pivotal in designing virtual reality-based paradigms for understanding perception and action in complex environments with potential translational benefits.

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Section: Neural Mechanismsmentioning

confidence: 86%

Section: Neural Mechanismsmentioning

confidence: 92%

Seeing Gravity: Gait Adaptations to Visual and Physical Inclines – A Virtual Reality Study

et al. 2020

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“…It is suggested that locomotor modulation following perceived gravitational changes while walking is mediated through an 'internal model of gravity' (Merfeld et al, 1999;Campos et al, 2014;Lacquaniti et al, 2014;Balestrucci et al, 2017) that integrates multisensory available cues such as vestibular, proprioceptive (aka body-based cues) and visual cues ( Figure 1). The exact role of vision in this process is yet unclear.…”

Section: Introductionmentioning

confidence: 99%

Vision affects gait speed but not patterns of muscle activation during inclined walking – a virtual reality study

Benady

Zadik

Ben-Gal

et al. 2020

Preprint

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While walking, our locomotion is affected by and adapts to the environment based on vision-based and body-based (vestibular and proprioception) cues, all contributing to an “Internal Model of Gravity”. During surface inclination transitions, we modulate gait to counteract gravitational forces by braking during downhill walking to avoid uncontrolled acceleration or by exerting effort to avoid deceleration while walking uphill. In this study, we investigated the role of vision in gait modulation during surface inclination transitions by using an immersive large-scale Virtual Reality (VR) system equipped with a self-paced treadmill and projected visual scenes that allowed us to modulate physical-visual inclinations congruence parametrically. Gait speed and leg muscle electromyography (EMG) were measured in 12 healthy young adults. In addition, the magnitude of subjective visual misperception of verticality was measured by the rod and frame test. During virtual (non-veridical) inclination transitions, vision modulated gait speed after transitions by (i) slowing down to counteract the excepted gravitational ‘boost’ in virtual downhill inclinations and by (ii) speeding up to counteract the expected gravity resistance in virtual uphill inclinations. These gait speed modulations were reflected in muscle activation intensity changes and associated with subjective visual verticality misperception. However, temporal patterns of muscle activation, which are significantly affected by real gravitational inclination transitions, were not affected by virtual (visual) inclination transitions. Our results delineate the contribution of vision to functional locomotion on uneven surfaces and may lead to enhanced rehabilitation strategies for neurological disorders affecting movement.Significance statementA crucial component of successful locomotion is maintaining balance and speed while walking on uneven surfaces. In order to reach successful locomotion, an individual must utilize multisensory integration of visual, gravitational, and proprioception cues. The contribution of vision to this process is still unclear, thus we used a fully immersive virtual reality treadmill setup allowing us to manipulate visual (virtual) and gravitational (real) surface inclinations independently during locomotion of healthy adults. While vision modulated gait speed for a short period after inclination transitions and this was predictive of individual’s visual dependency, muscle activation patterns were only affected by gravitational surface inclinations, not by vision. Understanding the vision’s contribution to successful locomotion may lead to improved rehabilitation for movement disorders.

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“…Weight-shifting, on the other hand, is a less automatized task that requires higher precision control, particularly when reaching close to the stability limits. The plane of motion could also be an important task constraint determining the impact of dynamic visual feedback cues on dynamic stability [40]. In the gait study, feedback was represented by a horizontal visual motion to inform about the instantaneous position of the pelvis and the trunk in the frontal plane, whereas in our paradigm, CoP feedback, provided by a vertically moving dot, did not seem to affect the stability of sway in the sagittal plane.…”

mentioning

confidence: 99%

Center of Pressure Feedback Modulates the Entrainment of Voluntary Sway to the Motion of a Visual Target

et al. 2019

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Visually guided weight shifting is widely employed in balance rehabilitation, but the underlying visuo-motor integration process leading to balance improvement is still unclear. In this study, we investigated the role of center of pressure (CoP) feedback on the entrainment of active voluntary sway to a moving visual target and on sway’s dynamic stability as a function of target predictability. Fifteen young and healthy adult volunteers (height 175 ± 7 cm, body mass 69 ± 12 kg, age 32 ± 5 years) tracked a vertically moving visual target by shifting their body weight antero-posteriorly under two target motion and feedback conditions, namely, predictable and less predictable target motion, with or without visual CoP feedback. Results revealed lower coherence, less gain, and longer phase lag when tracking the less predictable compared to the predictable target motion. Feedback did not affect CoP-target coherence, but feedback removal resulted in greater target overshooting and a shorter phase lag when tracking the less predictable target. These adaptations did not affect the dynamic stability of voluntary sway. It was concluded that CoP feedback improves spatial perception at the cost of time delays, particularly when tracking a less predictable moving target.

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Effects of visual motion consistent or inconsistent with gravity on postural sway

Cited by 26 publications

References 71 publications

Seeing Gravity: Gait Adaptations to Visual and Physical Inclines – A Virtual Reality Study

Seeing Gravity: Gait Adaptations to Visual and Physical Inclines – A Virtual Reality Study

Vision affects gait speed but not patterns of muscle activation during inclined walking – a virtual reality study

Center of Pressure Feedback Modulates the Entrainment of Voluntary Sway to the Motion of a Visual Target

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