FIG. 1.

A SCC coordinate system used for description of head rotation and 3D VOR eye rotation responses. +X, +Y, and +Z vectors intersect at the stereotactic origin (i.e., the midpoint of the interaural axis) and are perpendicular to the stereotactic coronal, sagittal, and horizontal planes, respectively (Della Santina et al. 2005b). Left-anterior/right-posterior (+LARP), right-anterior/left-posterior (+RALP), and +Z vectors represent the cardinal axes of the SCC coordinate system. Curved arrows depict the direction of positive rotation about each axis. B Thirty-eight unique vectors were selected to characterize the VOR responses to prosthetic stimulation. Each vector corresponds to a unique head rotation and desired eye response movement and contains three elements representing the stimulus intensity on each electrode (targeting the horizontal, superior, and posterior canal ampullary nerves). The direction of each vector represents the desired axis of eye rotation, and the length represents the magnitude of the desired eye velocity resulting from each . Ideally, eye rotations exclusively about the Z, LARP, or RALP axes would be elicited by electrical stimulation of only the left horizontal, left-anterior, or left-posterior canal electrodes, respectively.