Influence of Rotational Cues on the Neural Processing of Gravito-Inertial Force

Sensory systems often provide ambiguous information. For example, otolith organs measure gravito-inertial force (GIF), the sum of gravitational force and inertial force due to linear acceleration. According to Einstein’s equivalence principle, no set of linear accelerometers alone can distinguish gravitational force (which changes with head orientation during head tilt) from inertial force (which changes with linear acceleration of the head). Therefore, the central nervous system (CNS) must use other sensory cues to distinguish tilt from translation. For example, the CNS can use rotational cues provided by the semicircular canals and vision. Much of this chapter provides a brief review of studies showing the influence of rotational cues on the neural processing of tilt and translation. However, we also include preliminary unpublished data. We begin by discussing the underlying physics (and associated neural processes) and neural representations. We then present studies that measure the influence of rotational cues on tilt responses before presenting studies of translation responses. We finish by reviewing modeling approaches to sensory integration for both tilt and translation responses.