RT Journal Article
SR Electronic
T1 Violation of the Craniocentricity Principle for Vestibularly Evoked Balance Responses under Conditions of Anisotropic Stability
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 7696
OP 7703
DO 10.1523/JNEUROSCI.0733-14.2014
VO 34
IS 22
A1 Omar S. Mian
A1 Brian L. Day
YR 2014
UL http://www.jneurosci.org/content/34/22/7696.abstract
AB The balance response direction to electrically evoked vestibular perturbation is closely tied to head orientation. Such craniocentric response organization is expected of a simple error correction process. Here we ask whether this is maintained when the body is made more stable, but with the stability being greater in one direction than another. Since it is known that vestibularly evoked balance responses become smaller as body stability increases, the following two outcomes are possible: (1) response magnitude is attenuated, but with craniocentricity maintained; and (2) anisotropy of stability is considered such that components of the response are differentially attenuated, which would violate a craniocentric organizing principle. We tested these alternatives by measuring the direction of balance responses to electrical vestibular stimulation across a range of head orientations and stance widths in healthy humans. With feet together, the response was highly craniocentric. However, when stance width was increased so that the body was more stable in the frontal plane, response direction became biased toward the sagittal direction. This resulted in a nonlinear relationship between head orientation and response direction. While stance width changes the mechanical state of the body, the effect was also present when lateral light touch was used to produce anisotropy in stability, demonstrating that a significantly altered mechanical state was not crucial. We conclude that the balance system does not simply act according to the direction of vestibular input. Instead, it appears to assign greater relevance to components of vestibular input acting in the plane of lesser body stability than the plane of greater body stability, and acts accordingly.