Document Detail


Horizontal vestibuloocular reflex evoked by high-acceleration rotations in the squirrel monkey. I. Normal responses.
MedLine Citation:
PMID:  10482745     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The horizontal angular vestibuloocular reflex (VOR) evoked by high-frequency, high-acceleration rotations was studied in five squirrel monkeys with intact vestibular function. The VOR evoked by steps of acceleration in darkness (3,000 degrees /s(2) reaching a velocity of 150 degrees /s) began after a latency of 7.3 +/- 1.5 ms (mean +/- SD). Gain of the reflex during the acceleration was 14.2 +/- 5.2% greater than that measured once the plateau head velocity had been reached. A polynomial regression was used to analyze the trajectory of the responses to steps of acceleration. A better representation of the data was obtained from a polynomial that included a cubic term in contrast to an exclusively linear fit. For sinusoidal rotations of 0.5-15 Hz with a peak velocity of 20 degrees /s, the VOR gain measured 0.83 +/- 0.06 and did not vary across frequencies or animals. The phase of these responses was close to compensatory except at 15 Hz where a lag of 5.0 +/- 0.9 degrees was noted. The VOR gain did not vary with head velocity at 0.5 Hz but increased with velocity for rotations at frequencies of >/=4 Hz (0. 85 +/- 0.04 at 4 Hz, 20 degrees /s; 1.01 +/- 0.05 at 100 degrees /s, P < 0.0001). No responses to these rotations were noted in two animals that had undergone bilateral labyrinthectomy indicating that inertia of the eye had a negligible effect for these stimuli. We developed a mathematical model of VOR dynamics to account for these findings. The inputs to the reflex come from linear and nonlinear pathways. The linear pathway is responsible for the constant gain across frequencies at peak head velocity of 20 degrees /s and also for the phase lag at higher frequencies being less than that expected based on the reflex delay. The frequency- and velocity-dependent nonlinearity in VOR gain is accounted for by the dynamics of the nonlinear pathway. A transfer function that increases the gain of this pathway with frequency and a term related to the third power of head velocity are used to represent the dynamics of this pathway. This model accounts for the experimental findings and provides a method for interpreting responses to these stimuli after vestibular lesions.
Authors:
L B Minor; D M Lasker; D D Backous; T E Hullar
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of neurophysiology     Volume:  82     ISSN:  0022-3077     ISO Abbreviation:  J. Neurophysiol.     Publication Date:  1999 Sep 
Date Detail:
Created Date:  1999-11-01     Completed Date:  1999-11-01     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0375404     Medline TA:  J Neurophysiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1254-70     Citation Subset:  IM; S    
Affiliation:
Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Maryland 21287-0910, USA.
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MeSH Terms
Descriptor/Qualifier:
Acceleration
Animals
Models, Biological
Reaction Time / physiology
Reference Values
Reflex, Vestibulo-Ocular / physiology*
Rotation
Saimiri
Grant Support
ID/Acronym/Agency:
P60 DC-00979/DC/NIDCD NIH HHS; R01 DC-02390/DC/NIDCD NIH HHS; T32 DC-00027/DC/NIDCD NIH HHS
Investigator
Investigator/Affiliation:
M J Shelhamer / Johns Hopkins U Sch Med, Baltimore, MD

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


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