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Stabilization of posture by precision touch of the index finger with rigid and flexible filamentsLight touch of the index finger with a stationary surface at non-mechanically supportive force levels (<100 g) greatly attenuates the body sway of standing subjects. In three experiments, we evaluated the properties of finger contact and of the contacted object necessary to produce postural stabilization in subjects standing heel-to-toe with eyes closed, as well as how accurately hand position can be controlled. Experiment 1 involved finger contact with flexible filaments of different bending strengths, a flat surface, and an imagined spatial position. Contact with the flat surface was most effective in attenuating sway; the flexible filaments were much less effective but still significantly better than imagined contact. Experiment 2 compared the effectiveness of finger contact with a flexible filament, a rigid filament of the same diameter, a flat surface, and an imagined spatial position. The rigid filament and flat surface conditions were equally effective in attenuating body sway and were greatly superior to contact with the flexible filament, which was superior to imagined contact. Experiment 3 included five conditions: arms by sides; finger "contact" with an imagined spatial position; finger contact with a flat surface; finger contact with a flexible filament attempting to maintain it bent; and contact with the flexible filament attempting not to bend it. The arms by sides and finger "contact" with an imagined position conditions did not differ significantly; all three conditions involving actual finger contact showed significantly less center of pressure and hand sway, but contact with the flat surface was most effective in attenuating both postural and hand displacement. In all three experiments, the level of force applied in fingertip contact conditions was far below that necessary to provide mechanical stabilization. Our findings indicate that: (1) stimulation of a small number of receptors in the fingertip is adequate to allow stabilization of sway, (2) fingertip force levels as low as 5-10 g provide some stabilization, (3) contact with a stationary spatial referent is most effective, and (4) independent control of arm and torso occurs when finger contact is allowed.
Document ID
20040112303
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Lackner, J. R.
(Brandeis University Waltham, MA 02454-9110, United States)
Rabin, E.
DiZio, P.
Date Acquired
August 21, 2013
Publication Date
August 1, 2001
Publication Information
Publication: Experimental brain research. Experimentelle Hirnforschung. Experimentation cerebrale
Volume: 139
Issue: 4
ISSN: 0014-4819
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Neuroscience
Non-NASA Center
Clinical Trial

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