Although the vestibular system has exquisite sensitivity in signaling head movement in space, additional information about the orientation of the body in space is needed for the control of balance. Vestibular afferent information is interpreted and shaped in the context of proprioceptive and visual information. To achieve stable balance, it is likely that integration of vestibular and leg proprioceptive afferent signalsis critical, since the legs typically serve as the sole interface with the ground and limb position shapes vestibulospinal responses. However, virtually nothing is known about how limb afferent signals are integrated with vestibular afferent signals in central vestibular pathways. The primary goal of this application is to determine the influence of somatosensory limb inputs on the activity of vestibular nucleus (VN) neurons.
Three specific aims are proposed. In the first specific aim, we will characterize how hindlimb movements affect the responses of VN neurons to rotations of the head that activate labyrinthine receptors. We will additionally determine which subclass of VN neurons is sensitive to hindlimb movement. In the second specific aim, we will determine whether VN neurons differentiate between self-generated hindlimb movement and externally applied movement. In the third specific aim, we will determine whether hindlimb movement signals to VN neurons are amplified following loss of labyrinthine inputs, and substitute for the lost vestibular signals. These experiments are expected to advance understanding regarding the processing of limb somatosensory inputs in central vestibular pathways and may ultimately lead to novel therapies for vestibulopathic patients.
The proposed experiments will investigate the contributions of hindlimb proprioceptive signals to balance control through their influences on vestibular nucleus neurons. It is anticipated that the results of these experiments will ultimately suggest novel therapeutic treatment strategies for patients with balance disorders.
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