Mathematical Model for Interaction of Canals and Otoliths in Perception of Orientation, Translation, and Rotation.

Abstract : A computer model with six degress of freedom was developed in which linear acceleration along each axis is detected and directed along two channels. Output of one channel is perceived as a signal that was generated by gravity, produces no perception of translation, and is used to determine body orientation with respect to earth-vertical. Output of the other channel is perceived as a signal generated by transient linear acceleration and produces a perception of transnational motion. Attenuation of signals in these channels is controlled by computations that compare the angular velocity signal generated by the canals with the angular velocity of the input linear acceleration vector. The difference between these velocities serves as an error signal that increases the attenuation of the orientation channel and decreases the attenuation of the translation channel. Orientation channel outputs attenuate orthogonal canal signals that provide angular sensation and ocular reflexes. The model computes the following results that are consistent with empirical data reported in the literature: (1) For off-vertical rotation: bias and modulation components of nystagmus, faster decay of postrotatory nystagmus, attenuation of postrotatory turning sensations, and perceived conical translation; (2) For pendular centrifuge: vertical ascent and tumbling during deceleration; (3) For non pendular centrifuge: delay in perception of roll: and (4) For passive roll: no delay in perception.