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  • 1
    Electronic Resource
    Electronic Resource
    The importance of somatosensory information in triggering and scaling automatic postural responses in humans (1994)
    Springer
    Experimental brain research 101 (1994), S. 159-164 
    Details
    ISSN: 1432-1106
    Keywords: Posture ; Somatosensory ; Neuropathy EMG ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To clarify the role of somatosensory information from the lower limbs of humans in triggering and scaling the magnitude of automatic postural responses, patients with diabetic peripheral neuropathy and agematched normal controls were exposed to posterior horizontal translations of their support surface. Translation velocity and amplitude were varied to test the patients' ability to scale their postural responses to the magnitude of the translation. Postural response timing was quantified by measuring the onset latencies of three shank, thigh, and trunk muscles and response magnitude was quantified by measuring torque at the support surface. Neuropathy patients showed the same distalto-proximal muscle activation pattern as normal subjects, but the electromyogram (EMG) onsets in patients were delayed by 20–30 ms at all segments, suggesting an important role for somatosensory information from the lower limb in triggering centrally organized postural synergies. Patients showed an impaired ability to scale torque magnitude to both the velocity and amplitude of surface translations, suggesting that somatosensory information from the legs may be utilized for both direct sensory feedback and use of prior experience in scaling the magnitude of automatic postural responses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00243226
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of agonist/antagonist muscle vibration on human position sense (1990)
    Springer
    Experimental brain research 81 (1990), S. 573-580 
    Details
    ISSN: 1432-1106
    Keywords: Muscle spindles ; Agonist/antagonist muscle ; Forearm ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary During voluntary movement, muscle spindles of both the agonist and antagonist muscles potentially can supply information about position of the limb. Muscle vibration is known to increase muscle spindle discharge and cause systematic distortions of limb position sense in humans. The following two experiments attempted to examine these contributions by separately vibrating over the triceps and biceps muscles during forearm positioning. In the first experiment, subjects performed a horizontal flexion or extension of the right arm to a mechanical stop randomly positioned at 20, 40 or 60°. Vision was occluded and vibration was applied to the right arm. The perceived position of the right limb was assessed by instructing subjects to simultaneously match the right arm position with the left limb. Vibration of the shortening, agonist muscle had no effect on limb matching accuracy. However, antagonist muscle vibration resulted in a significant overestimation of the vibrated limb position by 6–13°. The procedures for the second experiment were similar to the first, except that movements of the right limb were self-terminated and only flexion movements were performed. A screen was mounted over the arms and subjects were instructed to move the right arm until it was positioned beneath a marker on the screen. Vibration of the shortening agonist muscle had no effect on either the positioning accuracy of the right limb or matching accuracy of the left limb. However, antagonist muscle vibration resulted in significantly shorter movements (6–10°) by the right limb and an overestimation of right limb position by the left, matching limb. These findings support the hypothesis that muscle spindle afferent information from the lengthening antagonist muscle contributes to limb position sense during voluntary movement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02423506
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Bilateral labyrinthectomy in the cat: motor behaviour and quiet stance parameters (1991)
    Springer
    Experimental brain research 85 (1991), S. 364-372 
    Details
    ISSN: 1432-1106
    Keywords: Posture ; Stance ; Balance ; Vestibular system ; Labyrinthectomy ; Ground reaction forces ; EMG ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The purpose of this study was to examine the effect of bilateral labyrinthectomy on quiet stance in the freely-standing cat. Since loss of the vestibular end organs produces marked deficits in motor behaviour, including ataxia and problems with balance, we hypothesized that labyrinthectomized animals would show impairment in quantitative measures of stance. Stance was quantified in terms of the ground reaction forces under each limb and the tonic electromyographic (EMG) activity of selected muscles. Animals were labyrinthectomized by drilling into the vestibule and removing the vestibular epithelium. Following lesion, animals were able to stand unsupported on the force platform within 2 days. To our surprise, the lesioned animals showed little change in stance parameters from the control, pre-lesion state. Thus, our hypothesis of changes in stance parameters was not supported. There was no change in the distribution of vertical forces under the limbs and no increase in sway, as measured by the area of excursion of the centre of pressure over time. The horizontal plane forces, which were diagonally directed prior to lesion, became more laterally directed and larger in amplitude. The change in direction persisted even after the animals had fully compensated for the lesion, but the force amplitudes returned to control values within 10–12 days. The change in horizontal force direction was similar to that observed in normal animals that were required to stand with their paws closer than preferred in the sagittal plane (unpublished observations). EMG activity changed in some muscles but not others, and usually transiently. One limb extensor showed decreases in tonic activity (gluteus medius), but other extensors showed increases (vastus medialis, soleus). It is likely that the changes in EMG levels were due to the biomechanics of the stance configuration related to the changes in direction of the horizontal plane forces. Kinematic recordings are needed to address this issue further.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229414
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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