Finite element modeling of the 3D otolith structure

Area of Science:

• Biomechanics
• Otolith Physiology
• Finite Element Analysis

Background:

• The otolithic membrane (OM) within the mammalian utricle is crucial for sensing gravity and linear acceleration.
• Understanding the mechanical behavior of the OM under static loads is essential for interpreting vestibular sensory information.

Purpose of the Study:

• To develop and utilize a 3D finite element model (FEM) of the guinea pig utricular otolith.
• To analyze the deformation of the OM under static loads, including gravity and endolymphatic pressure changes.
• To investigate the influence of various mechanical and geometrical parameters on OM displacement.

Main Methods:

• Development of a 3D FEM of the mammalian utricular otolith, incorporating gel and otoconial layers for the OM.
• Simulation of OM deformation under static loads (gravity, pressure) with varying mechanical parameters and gravity vector orientations.
• Analytical derivation of OM displacements caused by acceleration parallel to the macular plane.

Main Results:

• Estimated Young's modulus of the gel layer to be approximately 10^2 N/m^2 by comparing FEM results with experimental data.
• Demonstrated that static loads cause 3D local otolith displacements that are inhomogeneously distributed across the macular surface and otolith thickness.
• Identified that OM displacement distribution is dependent on geometrical and mechanical properties, including OM size, gel layer's Young's modulus, Poisson's ratio, and thickness.

Conclusions:

• The lowest part of the gel layer adjacent to the macular surface exhibits a significantly lower Young's modulus.
• The OM's border structure is optimized to minimize spatial inhomogeneity in gel layer displacement.
• Alterations in endolymphatic pressure can induce substantial deformation of the OM.