HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (9) Citing Articles via Google Scholar Google Scholar Articles by Highstein, S. M. Articles by Boyle, R. D. Search for Related Content PubMed PubMed Citation Articles by Highstein, S. M. Articles by Boyle, R. D.

INVITED REVIEW

Determinants of Spatial and Temporal Coding by Semicircular Canal Afferents

¹Department of Otolaryngology, Washington University School of Medicine, St. Louis, Missouri; ²Department of Bioengineering, University of Utah, Salt Lake City, Utah; ³Department of Neurology, Mount Sinai School of Medicine, New York, New York; ⁴National Aeronautics and Space Administration Ames BioVIS Technology Center, Moffett Field, California; and ⁵Marine Biological Laboratory, Woods Hole, Massachusetts

Submitted 19 May 2004; accepted in final form 29 November 2004

ABSTRACT

The vestibular semicircular canals are internal sensors that signal the magnitude, direction, and temporal properties of angular head motion. Fluid mechanics within the 3-canal labyrinth code the direction of movement and integrate angular acceleration stimuli over time. Directional coding is accomplished by decomposition of complex angular accelerations into 3 biomechanical components—one component exciting each of the 3 ampullary organs and associated afferent nerve bundles separately. For low-frequency angular motion stimuli, fluid displacement within each canal is proportional to angular acceleration. At higher frequencies, above the lower corner frequency, real-time integration is accomplished by viscous forces arising from the movement of fluid within the slender lumen of each canal. This results in angular velocity sensitive fluid displacements. Reflecting this, a subset of afferent fibers indeed report angular acceleration to the brain for low frequencies of head movement and report angular velocity for higher frequencies. However, a substantial number of afferent fibers also report angular acceleration, or a signal between acceleration and velocity, even at frequencies where the endolymph displacement is known to follow angular head velocity. These non-velocity-sensitive afferent signals cannot be attributed to canal biomechanics alone. The responses of non-velocity-sensitive cells include a mathematical differentiation (first-order or fractional) imparted by hair-cell and/or afferent complexes. This mathematical differentiation from velocity to acceleration cannot be attributed to hair cell ionic currents, but occurs as a result of the dynamics of synaptic transmission between hair cells and their primary afferent fibers. The evidence for this conclusion is reviewed below.

This article has been cited by other articles:

				R. A. Eatock, J. Xue, and R. Kalluri Ion channels in mammalian vestibular afferents may set regularity of firing J. Exp. Biol., June 1, 2008; 211(11): 1764 - 1774. [Abstract] [Full Text] [PDF]

				J. C. Holt, J.-T. Xue, A. M. Brichta, and J. M. Goldberg Transmission Between Type II Hair Cells and Bouton Afferents in the Turtle Posterior Crista J Neurophysiol, January 1, 2006; 95(1): 428 - 452. [Abstract] [Full Text] [PDF]

				J. Xue and E. H. Peterson Hair Bundle Heights in the Utricle: Differences Between Macular Locations and Hair Cell Types J Neurophysiol, January 1, 2006; 95(1): 171 - 186. [Abstract] [Full Text] [PDF]