Orientation of the Rotation-Axis Relative to Gravity: Its Influence on Nystagmus and the Sensation of Rotation

Evidence for a Test of Dynamic Otolith Function Considered in Relation to Responses from a Patient with Idiopathic Progressive Vestibular Degeneration,

“…This additional Input comes from the vestibular structures; men with bilateral loss of labyrinthine function do not yield an unequivocal nystagmus i,%;sponse during rotation about an Earth-horizontal axis, and their subjective experiences are quite different from those of men with nori-al function (5). Conflicting views have been expressed concerning the specific vestibular mechanisms responsible for thic kind of persistent nystagmus.…”

“…When the rotation axis is horizontal but all other aspects of the rotation are the same, nystagrnus persists for as long as the rotation continues (1,5). The important d;fference in these two stimulus situations is as follows: When the rotation axis is vertical, the vestibular structures maintain a constant crientation relative to gravity, and it is well known that the horizontal vestibular nystagmus in this situation depends upon stimulatior nf the hor~zontal semicircular canals by angular acceleration.…”

Nystagmus Responses during Rotation about a Tilted Axis,

“…An clternative view (12) ascribes the bias to a dynamic otolithic mechanism capable of extracting information regarding both the rate and direction of the rotating IPnear acceleration vector. The utricle lies approximately in the plane of rotation; so, during rotation about a tilted or horizontal axis the utricular statoconial mass would undergo a circular orbital motion relative to the underlying hair cells.…”

“…The rotary device used in this experiment has been described previously (12). The device, as used here, consisted of a padded platform upon which the subject was positioned with his longitudinal body axis aligned at the desired angle relative to gravity.…”

Spinning versus Wobbling: How the Brain Solves a Geometry Problem

“…1 B). Primates and certain other species have developed mechanisms to efficiently use the vestibular afferent signals for gaze stabilization through vestibulo-ocular reflexes (VORs) (Guedry, 1965;Young and Henn, 1975;Raphan et al, 1981;Cohen et al, 1983;Harris, 1987;Hess and Dieringer, 1990;Hess and Angelaki, 1993;Angelaki and Hess, 1996a,b;Kushiro et al, 2002). Pertinent observations suggest that the brain estimates head motion in space by processing the vestibular information based on an internal model of head-in-space motion (Merfeld et al, 1999;Angelaki et al, 2004).…”