Fig. 1.
(A) Three parameters define a cathodic-first, symmetric, biphasic, electrical stimulation pulse: current amplitude, pulse duration (PD), and interphase gap (IPG). T = time interval between pulse pairs. (B) The stimulus encoding scheme used for each of three dimensions of head rotation converts head velocity about a given semicircular canal axis to modulation of pulse rate f = 1/T on the corresponding electrodes via a piecewise-linear velocity-to-pulse rate mapping meant to efficiently approximate the mean operating characteristic of vestibular nerve afferent fibers. Stimulus intensity = 100% is depicted here.