Responses of caudal vestibular nucleus neurons of conscious cats to rotations in vertical planes, before and after a bilateral vestibular neurectomy.

Department of Otolaryngology, University of Pittsburgh, Room 519, Eye and Ear Institute, Pittsburgh, PA 15213, USA.
Experimental Brain Research (Impact Factor: 2.04). 06/2008; 188(2):175-86. DOI: 10.1007/s00221-008-1359-z
Source: PubMed


Although many previous experiments have considered the responses of vestibular nucleus neurons to rotations and translations of the head, little data are available regarding cells in the caudalmost portions of the vestibular nuclei (CVN), which mediate vestibulo-autonomic responses among other functions. This study examined the responses of CVN neurons of conscious cats to rotations in vertical planes, both before and after a bilateral vestibular neurectomy. None of the units included in the data sample had eye movement-related activity. In labyrinth-intact animals, some CVN neurons (22%) exhibited graviceptive responses consistent with inputs from otolith organs, but most (55%) had dynamic responses with phases synchronized with stimulus velocity. Furthermore, the large majority of CVN neurons had response vector orientations that were aligned either near the roll or vertical canal planes, and only 18% of cells were preferentially activated by pitch rotations. Sustained head-up rotations of the body provide challenges to the cardiovascular system and breathing, and thus the response dynamics of the large majority of CVN neurons were dissimilar to those of posturally-related autonomic reflexes. These data suggest that vestibular influences on autonomic control mediated by the CVN are more complex than previously envisioned, and likely involve considerable processing and integration of signals by brainstem regions involved in cardiovascular and respiratory regulation. Following a bilateral vestibular neurectomy, CVN neurons regained spontaneous activity within 24 h, and a very few neurons (<10%) responded to vertical tilts <15 degrees in amplitude. These findings indicate that nonlabyrinthine inputs are likely important in sustaining the activity of CVN neurons; thus, these inputs may play a role in functional recovery following peripheral vestibular lesions.

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    • "Experiments on animal subjects with induced BVH have shown that non-labyrinthine inputs rapidly restore resting activity in the vestibular nuclei (Waespe et al., 1992; Ris and Godaux, 1998; Miller et al., 2008) and can modulate this neural activity during some changes in body position (Yates et al., 2000; Miller et al., 2008). An important line of investigation is to determine whether nonlabyrinthine effects on activity in the vestibular system can be strengthened following BVH, and whether the information can be effectively utilized to compensate for deficits. "
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