Multiscale modeling of mechanotransduction in the utricle

Abstract

We review recent progress in using numerical models to relate utricular hair bundle and otoconial membrane (OM) structure to the functional requirements imposed by natural behavior in turtles. The head movements section reviews the evolution of experimental attempts to understand vestibular system function with emphasis on turtles, including data showing that accelerations occurring during natural head movements achieve higher magnitudes and frequencies than previously assumed. The structure section reviews quantitative anatomical data documenting topographical variation in the structures underlying macromechanical and micromechanical responses of the turtle utricle to head movement: hair bundles, OM, and bundle-OM coupling. The macromechanics section reviews macromechanical models that incorporate realistic anatomical and mechanical parameters and reveal that the system is significantly underdamped, contrary to previous assumptions. The micromechanics: hair bundle motion and met currents section reviews work based on micromechanical models, which demonstrates that topographical variation in the structure of hair bundles and OM, and their mode of coupling, result in regional specializations for signaling of low frequency (or static) head position and high frequency head accelerations. We conclude that computational models based on empirical data are especially promising for investigating mechanotransduction in this challenging sensorimotor system.

Tiltable objective microscope visualizes discrimination of static and dynamic head movement originates at hair cells

“…The functional difference between the striolar and extrastriolar HCs may be attributed to either or combination of the following mechanisms. First, hair-bundle shape and mechanical coupling between otolith and hair bundles differ across striolar and extrastriolar regions, which is thought to tune HCs to different stimulus frequency ranges 9,23,[36][37][38][39][40][41] . Second, the MET currents per unit hair-bundle de ection may differ between HCs 42 .…”

Vestibular Deficits in Deafness: Clinical Presentation, Animal Modeling, and Treatment Solutions

“…However, few studies to date have addressed the precise architecture of vestibular hair bundles in vestibular organs and their variations, or the variation of the position of these hair bundles in a given suborgan. Several groups have shown that the hair bundles of type I hair cells are wider than those of type II hair cells, with taller stereocilia, arranged to form a steeper bundle slope ( 44 , 62 , 72 , 73 ). This architecture may translate into type I bundle responses displaying a phase advance relative to those of type II hair cells.…”

Evidence-based diagnostic use of VEMPs

“…Fig. 2a; [58,69]). During constant or low-frequency linear acceleration, the otolith organs work as accelerometers, i.e., the otoconial membrane lags behind the underlying neuro-epithelium due to the inertia of the otoconia, thus, causing a relative movement between the two layers that is opposite to the direction of linear acceleration (.…”

“…The otolith (macula) organs sense linear acceleration, the utricle predominantly in the horizontal plane and the saccule predominantly in the vertical plane (Fig. 2 a; [ 58 , 69 ]). During constant or low-frequency linear acceleration, the otolith organs work as accelerometers, i.e., the otoconial membrane lags behind the underlying neuro-epithelium due to the inertia of the otoconia, thus, causing a relative movement between the two layers that is opposite to the direction of linear acceleration (Figs.…”