The Anatomical and Physiological Basis of Clinical Tests of Otolith Function. A Tribute to Yoshio Uchino

Abstract

Otolithic receptors are stimulated by gravitoinertial force (GIF) acting on the otoconia resulting in deflections of the hair bundles of otolithic receptor hair cells. The GIF is the sum of gravitational force and the inertial force due to linear acceleration. The usual clinical and experimental tests of otolith function have used GIFs (roll tilts re gravity or linear accelerations) as test stimuli. However, the opposite polarization of receptors across each otolithic macula is puzzling since a GIF directed across the otolith macula will excite receptors on one side of the line of polarity reversal (LPR at the striola) and simultaneously act to silence receptors on the opposite side of the LPR. It would seem the two neural signals from the one otolith macula should cancel. In fact, Uchino showed that instead of canceling, the simultaneous stimulation of the oppositely polarized hair cells enhances the otolithic response to GIF-both in the saccular macula and the utricular macula. For the utricular system there is also commissural inhibitory interaction between the utricular maculae in each ear. The results are that the one GIF stimulus will cause direct excitation of utricular receptors in the activated sector in one ear as well as indirect excitation resulting from the disfacilitation of utricular receptors in the corresponding sector on the opposite labyrinth. There are effectively two complementary parallel otolithic afferent systems-the sustained system concerned with signaling low frequency GIF stimuli such as roll head tilts and the transient system which is activated by sound and vibration. Clinical tests of the sustained otolith system-such as ocular counterrolling to roll-tilt or tests using linear translation-do not show unilateral otolithic loss reliably, whereas tests of transient otolith function [vestibular evoked myogenic potentials (VEMPs) to brief sound and vibration stimuli] do show unilateral otolithic loss. The opposing sectors of the maculae also explain the results of galvanic vestibular stimulation (GVS) where bilateral mastoid galvanic stimulation causes ocular torsion position similar to the otolithic response to GIF. However, GVS stimulates canal afferents as well as otolithic afferents so the eye movement response is complex.

An Integrated Perspective of Evolution and Development: From Genes to Function to Ear, Lateral Line and Electroreception

“…In zebrafish, it was further shown that, while early-born afferent neurons connect hair cells to the Mauthner cell, those occurring later only project to the central nucleus [210]. Modified after [22,37,47,196,211,212].…”

“…It appears that a bistable situation then determines of Emx2 in the rostral sibling through Notch-mediated lateral inhibition, which then determines the caudal position for the kinocilium of the rostral sibling and the emergence of the opposing polarity [23]. [22,37,47,196,211,212].…”

Study on the Perception Mechanism of Utricles Based on Bionic Models

“…At present, the relationship between utricle diseases and structural lesions or functional abnormalities is not very clear in the clinic [11]. To deeply understand the working principle of the complex and subtle otoliths and accurately judge the specific causes and locations of abnormal utricle function, it is necessary to understand the detailed perception mechanism of the utricle.…”

Vestibular contributions to the Romberg test: Testing semicircular canal and otolith function

“…Details of how the vestibular system really works started to be elucidated by Mach (1838–1916) [8], Crum Brown (1838–1922) [9], Breuer (1842–1925) [10], Hőgyes (1847–1906) [11], Ewald (1855–1921) [12], Bárány (1876–1936) [13], Lorente de No (1902–1990) [14], Lowenstein (1906–1999) [15] and others [16]. The journey continues to the present day [17,18]. The first articles we could find in Deutsche Zeitschrift f .…”