Violation of the Craniocentricity Principle for Vestibularly Evoked Balance Responses under Conditions of Anisotropic Stability

TY - JOUR

T1 - Violation of the Craniocentricity Principle for Vestibularly Evoked Balance Responses under Conditions of Anisotropic Stability

AU - Mian, Omar S

AU - Day, Brian L

N1 - Copyright © 2014 Mian and Day.

PY - 2014/5/28

Y1 - 2014/5/28

N2 - 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.

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.

KW - Adolescent

KW - Adult

KW - Anisotropy

KW - Evoked Potentials, Somatosensory

KW - Female

KW - Humans

KW - Male

KW - Postural Balance

KW - Vestibule, Labyrinth

KW - Young Adult

U2 - 10.1523/JNEUROSCI.0733-14.2014

DO - 10.1523/JNEUROSCI.0733-14.2014

M3 - Article

C2 - 24872573

SN - 0270-6474

VL - 34

SP - 7696

EP - 7703

JO - JOURNAL OF NEUROSCIENCE

JF - JOURNAL OF NEUROSCIENCE

IS - 22

ER -