Modeling the relation between head orientations and otolith responses in humans.

We have performed a finite element simulation of realistic displacements of otolith membranes by static linear accelerations. The simulations were based on accurate measurements of the surfaces of human utricular and saccular maculae, which indicate a clear curvature of these surfaces. The results show that this curvature, a feature probably found in all mammals, has no effect on the mechanics of the structure as a whole since the elastic coupling in the otolith membrane is insufficient. Hair cell excitations on any place of the macula are only affected by the local orientation of the macula with respect to acceleration. Based on the displacements of the otolith membrane, we also calculated the induced activation patterns on the otolith epithelia. These patterns provide for the first time a complete image of peripheral otolith activity. The individual activation patterns at selected locations on the macula correspond well with single cell recordings of actual peripheral otolith neurons.