Secret laws of the labyrinth

This abstract presents new results on the structure and function of vestibular part of the inner ear of vertebrates with special emphasis on human behavior. First we summarize a mathematical analysis of motion of the endolymphatic fluid, justifying known approximated formulas for the cupula functioning based on a set of anatomical parameters. Some of these parameters can be estimated from the bony labyrinth, some others cannot be. We present original data issued from synchrotron microtomography (Sμ CT) of five tetrapod species, allowing to compare bony and membranous labyrinths. We derive several simple and robust empirical laws connecting membranous parameters and bony parameters. Then, using published results on human labyrinths (Bradshaw et al. 2009), we deduce functional consequences for the human labyrinths. For instance we show that, contrarily to current belief, the kinematic sensitivity for yaw is larger than for pitch and roll.