Postural responses to combined vestibular and hip proprioceptive stimulation in man

Abstract

Vestibular-proprioceptive interaction in human postural control in the frontal plane was studied by analysing the lateral body sway evoked in a standing subject by a weak, near-threshold galvanic vestibular stimulation combined with a balanced, bilateral vibration of the medial gluteus muscles. The intensities of the stimuli were adjusted so that none of them produced a consistent postural response when delivered alone. The pattern of the lateral body sway evoked by the combined stimulation was compared with postural responses to suprathreshold vestibular stimulation and asymmetric (unilateral) vibration of the hip abductors. During the vestibular stimulation alone the head movement started earlier and was larger than movement of the hip. During unilateral vibration the head movement was delayed with respect to the hip movement and the amplitude of head deviation was less than that of the hip. The pattern of postural response to combined vestibular stimulation and balanced vibration resembled that observed under unbalanced, unilateral vibration in terms of both the latencies and amplitudes of deviation of the body segments from their respective baseline positions. It is suggested that the asymmetric vestibular signal provided by galvanic stimulation of the labyrinth introduces a bias into the reference frame for central interpretation of proprioceptive signals so that a symmetric proprioceptive input gives rise to a lateral body sway when referenced to an asymmetric vestibular input.

Cortical facilitation of proprioceptive inputs related to gravitational balance constraints during step preparation

“…A suggestion was made that it could result from the absence of gravity-based vestibular inputs, which would lead to a decreased vestibulospinal influence on muscle spindle sensitivity (Lackner and DiZio 1992). This hypothesis is supported by the observation made by Popov et al (1999): a balanced bilateral vibration of the hip abductors, which is inappropriate for eliciting a postural response, does evoke a body sway when it is combined with a near-threshold galvanic vestibular stimulation, which is too weak to elicit a postural response on its own. Another explanation for the decreased SEP in microgravity could be related to the absence of gravityinduced joint torques.…”

Neck muscle vibration makes walking humans accelerate in the direction of gaze

“…One approach to probe the role of proprioception in posture and movement consists of applying vibrations to muscles or tendons (thereby activating mainly muscle spindle afferents; Bianconi & van der Meulen, 1963; Goodwin et al 1972; Burke et al 1976). When applied to a standing human subject, muscle vibration induces several effects (from illusions of ego‐ or exo‐motion to actual body sway) that depend on the muscle vibrated, the sensory context and the task (Eklund, 1972; Lackner & Levine, 1979; Roll et al 1989, 1998; Quoniam et al 1990; Smetanin et al 1993; Ivanenko et al 1999 b ; Kavounoudias et al 1999; Popov et al 1999).…”

Do Gravity-Related Sensory Information Enable the Enhancement of Cortical Proprioceptive Inputs When Planning a Step in Microgravity?

“…This area is known to be involved in the whole body experience built up from multisensory integration [61] and has dense connections with the somatosensory cortex [62]. Behavioural studies have also highlighted such potentiation processes when combining lower leg muscle vibration and galvanic vestibular stimulation in postural control [63],[64] and during locomotion [65]. A representative example of somatosensory and vestibular interaction was also highlighted by Horak and Hlavačka [66] who showed on patients with somatosensory loss caused by peripheral neuropathy, an increased vestibulospinal sensitivity.…”