The altered vestibular-evoked myogenic and whole-body postural responses in old men during standing

Dalton, Brian H.; Blouin, Jean‐Sébastien; Allen, Matti D.; Rice, Charles L.; Inglis, James

doi:10.1016/j.exger.2014.09.020

Cited by 37 publications

(22 citation statements)

References 64 publications

(121 reference statements)

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“…When a person is asked to target a force level or to follow a simple muscle activation pattern, it has been proposed that an increased force variability (loss of steadiness) is related to MU remodelling in that smooth graded control is affected negatively by having fewer larger units, a greater concentration of one type of unit, and increased MU train variability in firing rates (Christou, 2011). These same features may then translate into problems with balance, consistent with evidence that postural sway is greater in older adults and that their recovery from postural perturbations is blunted (Enoka et al 2003;Dalton et al 2014;Kanekar & Aruin, 2014). An impaired ability to rapidly initiate and generate muscle force, whether isometrically or dynamically, will result in a neuromuscular response that is insufficient to withstand a perturbation or to adequately compensate before task failure.…”

Section: Functional Consequences Of Age-related Motor Unit Remodellingmentioning

confidence: 76%

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Innervation and neuromuscular control in ageing skeletal muscle

Hepple

Rice

2015

The Journal of Physiology

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296

280

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Changes in the neuromuscular system affecting the ageing motor unit manifest structurally as a reduction in motor unit number secondary to motor neuron loss; fibre type grouping due to repeating cycles of denervation-reinnervation; and instability of the neuromuscular junction that may be due to either or both of a gradual perturbation in postsynaptic signalling mechanisms necessary for maintenance of the endplate acetylcholine receptor clusters or a sudden process involving motor neuron death or traumatic injury to the muscle fibre. Functionally, these changes manifest as a reduction in strength and coordination that precedes a loss in muscle mass and contributes to impairments in fatigue. Regular muscle activation in postural muscles or through habitual physical activity can attenuate some of these structural and functional changes up to a point along the ageing continuum. On the other hand, regular muscle activation in advanced age (>75 years) loses its efficacy, and at least in rodents may exacerbate age-related motor neuron death. Transgenic mouse studies aimed at identifying potential mechanisms of motor unit disruptions in ageing muscle are not conclusive due to many different mechanisms converging on similar motor unit alterations, many of which phenocopy ageing muscle. Longitudinal studies of ageing models and humans will help clarify the cause and effect relationships and thus, identify relevant therapeutic targets to better preserve muscle function across the lifespan. Abbreviations AChR, acetylcholine receptor; MHC, myosin heavy chain; MU, motor unit.

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Section: Functional Consequences Of Age-related Motor Unit Remodellingmentioning

confidence: 76%

“…; Dalton et al . ; Kanekar & Aruin, ). An impaired ability to rapidly initiate and generate muscle force, whether isometrically or dynamically, will result in a neuromuscular response that is insufficient to withstand a perturbation or to adequately compensate before task failure.…”

Section: Introductionmentioning

confidence: 99%

Innervation and neuromuscular control in ageing skeletal muscle

Hepple

Rice

2015

The Journal of Physiology

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296

280

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“…; Reynolds, ; Dalton et al . ). For the purposes of this study, we are interested in the medium latency response as it represents a whole‐body postural reaction to a vestibular error signal (Mian & Day, , ; Mian et al .…”

Section: Methodsmentioning

confidence: 97%

The internal representation of head orientation differs for conscious perception and balance control

Dalton

Rasman

Inglis

et al. 2017

The Journal of Physiology

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Vestibular signals used for balance control must be integrated with other sensorimotor cues to allow transformation of descending signals according to an internal representation of body configuration. We explored two alternative models of sensorimotor integration that propose (1) a single internal representation of head-on-feet orientation is responsible for perceived postural orientation and standing balance or (2) conscious perception and balance control are driven by separate internal representations. During three experiments, participants stood quietly while passively or actively maintaining a prolonged head-turned posture (>10 min). Throughout the trials, participants intermittently reported their perceived head angular position, and subsequently electrical vestibular stimuli were delivered to elicit whole-body balance responses. Visual recalibration of head-on-feet posture was used to determine whether static visual cues are used to update the internal representation of body configuration for perceived orientation and standing balance. All three experiments involved situations in which the vestibular-evoked balance response was not orthogonal to perceived head-on-feet orientation, regardless of the visual information provided. For prolonged head-turned postures, balance responses consistent with actual head-on-feet posture occurred only during the active condition. Our results indicate that conscious perception of head-on-feet posture and vestibular control of balance do not rely on the same internal representation, but instead treat sensorimotor cues in parallel and may arrive at different conclusions regarding head-on-feet posture. The balance system appears to bypass static visual cues of postural orientation and mainly use other sensorimotor signals of head-on-feet position to transform vestibular signals of head motion, a mechanism appropriate for most daily activities.

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“…This may be compensated for by upweighting of the other sensory information, resulting in a higher visual and/or proprioceptive weight. However, others have argued that vestibular information plays an important role during standing balance by showing a larger vestibular-evoked balance response in healthy elderly men compared with healthy young men (Dalton et al 2014). However, to investigate whether both vestibular and proprioceptive information are used relatively more by healthy elderly compared with healthy young, experiments with multiple simultaneous sensory disturbances must be performed.…”

Section: More Use Of Proprioceptive Information With Agementioning

confidence: 99%

Changes in sensory reweighting of proprioceptive information during standing balance with age and disease

Pasma

Engelhart

Maier

et al. 2015

Journal of Neurophysiology

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With sensory reweighting, reliable sensory information is selected over unreliable information during balance by dynamically combining this information. We used system identification techniques to show the weight and the adaptive process of weight change of proprioceptive information during standing balance with age and specific diseases. Ten healthy young subjects (aged between 20 and 30 yr) and 44 elderly subjects (aged above 65 yr) encompassing 10 healthy elderly, 10 with cataract, 10 with polyneuropathy, and 14 with impaired balance, participated in the study. During stance, proprioceptive information of the ankles was disturbed by rotation of the support surface with specific frequency content where disturbance amplitude increased over trials. Body sway and reactive ankle torque were measured to determine sensitivity functions of these responses to the disturbance amplitude. Model fits resulted in a proprioceptive weight (changing over trials), time delay, force feedback, reflexive stiffness, and damping. The proprioceptive weight was higher in healthy elderly compared with young subjects and higher in elderly subjects with cataract and with impaired balance compared with healthy elderly subjects. Proprioceptive weight decreased with increasing disturbance amplitude; decrease was similar in all groups. In all groups, the time delay was higher and the reflexive stiffness was lower compared with young or healthy elderly subjects. In conclusion, proprioceptive information is weighted more with age and in patients with cataract and impaired balance. With age and specific diseases the time delay was higher and reflexive stiffness was lower. These results illustrate the opportunity to detect the underlying cause of impaired balance in the elderly with system identification.

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The altered vestibular-evoked myogenic and whole-body postural responses in old men during standing

Cited by 37 publications

References 64 publications

Innervation and neuromuscular control in ageing skeletal muscle

Innervation and neuromuscular control in ageing skeletal muscle

The internal representation of head orientation differs for conscious perception and balance control

Changes in sensory reweighting of proprioceptive information during standing balance with age and disease

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