The Role of the Vestibular System in Relation to Muscle Tone and Postural Reflexes in Man

Molina-Negro, P; Bertrand, Robert A.; And, E. Martin; Gioani, Y.

doi:10.3109/00016488009127170

Cited by 18 publications

(12 citation statements)

References 12 publications

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“…ClØ-ment et al (1984) found an increase in tonic ankle flexor activity combined with a decrease in tonic extensor activity during space flight, which if carried over postflight could lead to a reduction in the stiffness about the ankle joint against gravitational loads. It is well established that suppression of vestibular function results in depression of the gamma-static innervation to the leg extensors, causing reduction in extensor tone (Molina-Negro et al 1980). However, because relative enhancement of the knee flexor was not observed, ClØments group viewed the changes at the ankle as a ªsubject-initiated postural strategyª rather than a functional deafferentation of the otoliths due to microgravity.…”

Section: Limb Stiffnessmentioning

confidence: 99%

Altered astronaut lower limb and mass center kinematics in downward jumping following space flight

1997

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Astronauts exposed to the microgravity conditions encountered during space flight exhibit postural and gait instabilities upon return to earth that could impair critical postflight performance. The aim of the present study was to determine the effects of microgravity exposure on astronauts' performance of two-footed jump landings. Nine astronauts from several Space Shuttle missions were tested both preflight and postflight with a series of voluntary, two-footed downward hops from a 30-cm-high step. A video-based, three-dimensional motion-analysis system permitted calculation of body segment positions and joint angular displacements. Phase-plane plots of knee, hip, and ankle angular velocities compared with the corresponding joint angles were used to describe the lower limb kinematics during jump landings. The position of the whole-body center of mass (COM) was also estimated in the sagittal plane using an eight-segment body model. Four of nine subjects exhibited expanded phase-plane portraits postflight, with significant increases in peak joint flexion angles and flexion rates following space flight. In contrast, two subjects showed significant contractions of their phase-plane portraits postflight and three subjects showed insignificant overall changes after space flight. Analysis of the vertical COM motion generally supported the joint angle results. Subjects with expanded joint angle phase-plane portraits postflight exhibited larger downward deviations of the COM and longer times from impact to peak deflection, as well as lower upward recovery velocities. Subjects with postflight joint angle phase-plane contraction demonstrated opposite effects in the COM motion. The joint kinematics results indicated the existence of two contrasting response modes due to microgravity exposure. Most subjects exhibited "compliant" impact absorption postflight, consistent with decreased limb stiffness and damping, and a reduction in the bandwidth of the postural control system. Fewer subjects showed "stiff" behavior after space flight, where contractions in the phase-plane portraits pointed to an increase in control bandwidth. The changes appeared to result from adaptive modifications in the control of lower limb impedance. A simple 2nd-order model of the vertical COM motion indicated that changes in the effective vertical stiffness of the legs can predict key features of the postflight performance. Compliant responses may reflect inflight adaptation due to altered demands on the postural control system in microgravity, while stiff behavior may result from overcompensation postflight for the presumed reduction in limb stiffness inflight.

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Section: Limb Stiffnessmentioning

confidence: 99%

Altered astronaut lower limb and mass center kinematics in downward jumping following space flight

1997

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“…Vestibulospinal drive is also an important facilitator of the tonic vibration reflex (Gillies et al, 1971a, b), a useful analog for the tonic stretch reflex (Kimura, 2013). Surgical transection of the vestibular nerve or interruption of central vestibular pathways results in a marked decrease in the tonic vibration reflex (Gillies et al, 1971a, b), motoneuron excitability (Molina-Negro et al, 1980) and antigravity muscle tone (Bach and Magoun, 1947), highlighting the potentially unique contributions of the vestibular nuclei.…”

Section: Introductionmentioning

confidence: 99%

Asymmetries in vestibular evoked myogenic potentials in chronic stroke survivors with spastic hypertonia: Evidence for a vestibulospinal role

Miller¹,

Klein²,

Suresh³

et al. 2014

Clinical Neurophysiology

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Objective Indirect evidence suggests that lateralized changes in motoneuron behavior post-stroke are potentially due to a depolarizing supraspinal drive to the motoneuron pool, but the pathways responsible are unknown. In this study, we assessed vestibular evoked myogenic potentials (VEMPs) in the neck muscles of hemispheric stroke survivors with contralesional spasticity to quantify the relative levels of vestibular drive to the spastic-paretic and contralateral motoneuron pools. Methods VEMPs were recorded from each sternocleidomastoid muscle in chronic stroke survivors. Side-to-side differences in cVEMP amplitude were calculated and expressed as an asymmetry ratio, a proxy for the relative amount of vestibular drive to each side. Results Spastic-paretic VEMPs were larger than contralateral VEMPs in 13/16 subjects. There was a strong positive relationship between the degree of asymmetry and the severity of spasticity in this subset of subjects. Remaining subjects had larger contralateral responses. Conclusion Vestibular drive to cervical motoneurons is asymmetric in spastic stroke survivors, supporting our hypothesis that there is an imbalance in descending vestibular drive to motoneuron pools post-stroke. We speculate this imbalance is a consequence of the unilateral disruption of inhibitory corticobulbar projections to the vestibular nuclei. Significance This study sheds new light on the underlying mechanisms of post-stroke spasticity.

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“…The vestibular system, interacting with proprioceptive and visual centers, provides critical information for the maintenance of head and body posture, eye position and movement, muscle tonus, and equilibrium (de Quiros, 1979;Eviatar and Eviatar, 1979;Molina-Negro et al, 1980;White et al, 1980). Interactions between these three systems, and the control exercised by the brainstem and cerebellum, are critical for the acquisition of developmental reflexes and in postural control (de Klejn, 1924;de Quiros, 1979;Magnus, 1924).…”

Section: An Overviewmentioning

confidence: 99%

“…The immediate reaction to a loss of balance while standing is a proprioceptive response. The vestibular apparatus does not react until after the proprioceptive response has taken place (de Klejn, 1924;Molina-Negro et al, 1980). The proprioceptive response to loss of balance is mediated at the spinal level,…”

Section: The Maintenance Of Balance and Posturementioning

confidence: 99%

The Vestibular System: Pediatric Considerations

Cyr¹

1983

Semin Hear

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The Role of the Vestibular System in Relation to Muscle Tone and Postural Reflexes in Man

Cited by 18 publications

References 12 publications

Altered astronaut lower limb and mass center kinematics in downward jumping following space flight

Altered astronaut lower limb and mass center kinematics in downward jumping following space flight

Asymmetries in vestibular evoked myogenic potentials in chronic stroke survivors with spastic hypertonia: Evidence for a vestibulospinal role

The Vestibular System: Pediatric Considerations

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