Document Detail

The effect of voluntary sway control on the early and late components of the vestibular-evoked postural response.
MedLine Citation:
PMID:  19779703     Owner:  NLM     Status:  MEDLINE    
Electrical stimulation of the human vestibular nerve evokes a postural response which, unlike visually evoked sway, is unaffected by stimulus predictability. However, responses can be modified by changes in the level of background sway. Here, the effect of voluntary changes in sway magnitude upon the response to vestibular stimulation is investigated. Subjects were asked to stand either relaxed or still while stochastic vestibular stimulation (SVS) was applied to the mastoid processes (1 mA root-mean-square; 0.05-5 Hz). Calf muscle activity, ground-reaction force and sway responses were characterised in the frequency and time domains using cross-spectra and cross-correlations (CC), respectively. SVS induced coherent EMG, lateral force and sway responses. Differences in response gain between still and relaxed conditions largely reflected differences in signal power across frequencies, and peak EMG CC responses correlated strongly with background EMG changes. However, when data were normalised to account for changes in signal power, early EMG responses were almost identical between conditions, but after 232 ms, they diverged. Standing still caused heavy attenuation of the late component of the EMG response, reducing response duration by 825 ms. Similar effects were observed in force and sway, and all postural signals showed less phase lag with SVS below 2 Hz when standing still. These results demonstrate that the vestibular-evoked postural response consists of two parts: an early high-frequency component, which scales with background activity but is otherwise inflexible, and a late low-frequency component, which can be heavily attenuated by voluntary control resulting in earlier termination of the sway response.
Raymond Francis Reynolds
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Publication Detail:
Type:  Journal Article     Date:  2009-09-25
Journal Detail:
Title:  Experimental brain research     Volume:  201     ISSN:  1432-1106     ISO Abbreviation:  Exp Brain Res     Publication Date:  2010 Mar 
Date Detail:
Created Date:  2010-03-05     Completed Date:  2010-05-25     Revised Date:  2013-12-13    
Medline Journal Info:
Nlm Unique ID:  0043312     Medline TA:  Exp Brain Res     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  133-9     Citation Subset:  IM    
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MeSH Terms
Acoustic Stimulation
Data Interpretation, Statistical
Evoked Potentials / physiology*
Leg / physiology
Muscle, Skeletal / physiology
Posture / physiology*
Stochastic Processes
Vestibule, Labyrinth / physiology*
Young Adult

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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