Journal of Vestibular Research - Volume 11, issue 1

Authors: Furman, Joseph M.

Article Type: Editorial

DOI: 10.3233/VES-2001-11101

Citation: Journal of Vestibular Research, vol. 11, no. 1, pp. 1-1, 2001

Authors: Kim, Ji Soo | Sharpe, James A.

Article Type: Research Article

Abstract: The effects of aging on the vertical vestibulo-ocular reflex (VOR), and its interactions with vision during active head motion had not been investigated. We measured smooth pursuit, combined eye-head tracking, the VOR, and its visual enhancement and cancellation during active head motion in pitch using a magnetic search coil technique in 21 younger (age < 65 ) and 10 elderly (age ⩾ 65 ) subjects. With the head immobile, subjects pursued a target moving sinusoidally with a frequency range of 0.125 to 2.0 Hz, and with peak target accelerations (PTAs) ranging from 12 to 789Âř/s 2 …. Combined eye-head tracking, the VOR in darkness, and its visual enhancement during fixation of an earth-fixed target (VVOR) were measured during active sinusoidal head motion with a peak-to-peak amplitude of 20Âř at frequencies of 0.25, 0.5, 1.0 and 2.0 Hz. The efficacy of VOR cancellation was determined from VOR gains during combined eye-head tracking. VOR and VVOR gains were symmetrical in both directions and did not change with aging, except for reduced gains of the downward VOR and VVOR at low frequency (0.25 Hz). However, in the elderly, smooth pursuit, and combined eye-head tracking gains and the efficacy of cancellation of the VOR were significantly lower than in younger subjects. In both the young and elderly groups, VOR gain in darkness did not vary with the frequency of active head motion while the gains of smooth pursuit, combined eye-head tracking, and VVOR declined with increasing target frequency. VOR and VVOR performance in the elderly implicates relative preservation of neural structures subserving vertical vestibular smooth eye motion in senescence. Show more

Keywords: vestibulo-ocular reflex, smooth pursuit, combined eye-head tracking, aging

DOI: 10.3233/VES-2001-11102

Citation: Journal of Vestibular Research, vol. 11, no. 1, pp. 3-12, 2001

Authors: Kondrachuk, Alexander V.

Article Type: Research Article

Abstract: A 3D finite element model (FEM) of the mammalian utricular otolith corresponding to spatial structure, shape and size of the otolith from the guinea pig was developed. The otolithic membrane (OM) was considered as consisting of gel and otoconial layers. The macular surface was approximated as a plane. The deformation of the OM under static loads such as gravity and the change of endolymphatic pressure was analyzed using the FEM for different mechanical parameters of the OM and for different gravity vector orientations. The analytical dependence of OM displacements caused by the acceleration parallel to the macular plane was obtained. …By comparison of the results of calculations with the known experimental data Young’s modulus of the gel layer was estimated to be of order of 10 N/m 2 . It was shown that static loads result in 3D local otolith displacements inhomogeneously distributed along the macular surface and across otolith thickness. Their distribution depends on the geometrical and mechanical parameters of the otolith components. The influences of the finite size of the OM, the Young’s modulus, Poisson’s ratio and thickness of the gel layer on the local displacements distribution of the OM were analyzed. The results of simulation suggest that: a) the Young’s modulus of the thin lowest part of the gel layer adjacent to the macular surface is much smaller than that of the rest of the OM; b) the structure of the border is designed to reduce the spatial inhomogeneity of the gel layer displacement; c) a change of the endolymphatic pressure may result in significant deformation of the OM. Show more

Keywords: finite element modeling, otolith, gravity, endolymphatic pressure

DOI: 10.3233/VES-2001-11103

Citation: Journal of Vestibular Research, vol. 11, no. 1, pp. 13-32, 2001

Authors: Kondrachuk, Alexander V.

Article Type: Research Article

Abstract: Dynamic behavior of an otolithic membrane (OM) was studied analytically using simplified homogeneous viscoelastic (Kelvin-Voight body) model of the OM. The OM was represented by a thin plate attached to a macular plane. Viscoelastic properties of the OM determine the specific times (T 1 and T 2 ) and frequency-dependent behavior of the local displacements of the membrane caused by the inertial time-dependent forces. Two kinds of an otolith stimulation were analyzed: step-function and harmonic accelerations of the membrane. Results of the modeling were compared with the known experimental …data to estimate the Young’s modulus E and viscosity μ of a gel layer: E is of order of 10 N/m 2 , μ is of order of 1 poise in the range of frequency 0.2–2 Hz. It has allowed us to estimate the values of T 1 (10 − 5 –10 − 6 sec) and T 2 (∼ 3 · 10 − 2 sec). A relationship of the motion equation of the OM with well-known overdamped pendulum model of the otolith was discussed. The model of stereocilia tip-links deformation in the case, when the HCBs passively follow gel deformation, was proposed and analyzed. It was shown that for slender and long HCBs with the lengths comparable to a thickness of effective gel layer, a relative deformation of the tip-links of stereocilia caused by OM acceleration depends on time and the distance from the macular plane. The results of the modeling suggest that this type of the HCB may be responsible for analysis of fine temporal (frequency) structure of the OM acceleration. Show more

Keywords: otolith, modeling, hair cell bundle, tip-links

DOI: 10.3233/VES-2001-11104

Citation: Journal of Vestibular Research, vol. 11, no. 1, pp. 33-42, 2001

Authors: Njeugna, E. | Kopp, C.M. | Eichhorn, J.-L.

Article Type: Research Article

Abstract: The aim of this paper is to determine the domain of validity of calculated quasi-static deformations of the cupula and of ciliar deflections on the crista ampullaris. Several three-dimensional models of the isolated ampullar diaphragm of the human semicircular canal and of that of the frog are studied theoretically by modal analysis. The four first modes of vibration are determined for each structure. Numerical simulations prove that for the first mode of vibration, the cupular deformation has the same shape as that obtained by applying a static pressure difference across the ampullar diaphragm. We studied also the effect of the …mechanical properties (Young's modulus and Poisson's coefficient) of the components of the ampullar diaphragm on the vibration modes and their frequencies. The condition, which must be satisfied by the cupular internal viscosity, to have resonance near the natural frequency of the ampullar diaphragm is determined. Show more

Keywords: semicircular canal, cupula, vestibule, vibration analysis

DOI: 10.3233/VES-2001-11105

Citation: Journal of Vestibular Research, vol. 11, no. 1, pp. 43-54, 2001

Authors: Dimitri, P.S. | Wall III, C. | Oas, J.G. | Rauch, S.D.

Article Type: Research Article

Abstract: Menière's disease (MD) and migraine associated dizziness (MAD) are two disorders that can have similar symptomatologies, but differ vastly in treatment. Vestibular testing is sometimes used to help differentiate between these disorders, but the inefficiency of a human interpreter analyzing a multitude of variables independently decreases its utility. Our hypothesis was that we could objectively discriminate between patients with MD and those with MAD using select variables from the vestibular test battery. Sinusoidal harmonic acceleration test variables were reduced to three vestibulo-ocular reflex physiologic parameters: gain, time constant, and asymmetry. A combination of these parameters plus a measurement of reduced …vestibular response from caloric testing allowed us to achieve a joint classification rate of 91%, independent quadratic classification algorithm. Data from posturography were not useful for this type of differentiation. Overall, our classification function can be used as an unbiased assistant to discriminate between MD and MAD and gave us insight into the pathophysiologic differences between the two disorders. Show more

Keywords: vestibulo-ocular reflex, time constant, decision analysis, Menière's disease, migraine

DOI: 10.3233/VES-2001-11106

Citation: Journal of Vestibular Research, vol. 11, no. 1, pp. 53-65, 2001