Vestibular Macular Mapping in Man

The normal histology and ultrastructure of the vestibular sensory regions are well known and have been previously described. In the mammalian vestibular maculae, a narrow strip, the striola, and large peripheral areas can be distinguished.'v2 Each vestibular sensory cell is equipped with a hair bundle consisting of many stercocilia and one k in~ci l ium.~ The orientation of the kinocilium determines the polarization of the hair b ~ n d l e . ~ Thc morphological polarization is the same over large areas, and its direction shifts along an imaginary line, which extends through the striola. In the macula utriculi the morphological polarization is directed from the periphery towards the s t r i ~ l a ; ' ~ ~ ~ ~ in the macula sacculi the opposite condition exists.lgG The bending of a hair bundle towards the kinocilium results in a depolarization of the hair ~ ~ 1 1 . ~ 9 ~ According to the pattern of the morphological polarization, a displacement of the whole statoconial membrane which covers the macula results in depolarization of some hair cells and hyperpolarization of others.