Bilateral Otolith Contribution to Spatial Coding in the Vestibular System

Abstract

Recent work on the coding of spatial information in central otolith neurons has significantly advanced our knowledge of signal transformation from head-fixed otolith coordinates to space-centered coordinates during motion. In this review, emphasis is placed on the neural mechanisms by which signals generated at the bilateral labyrinths are recognized as gravity-dependent spatial information and in turn as substrate for otolithic reflexes. We first focus on the spatiotemporal neuronal response patterns (i.e. one- and two-dimensional neurons) to pure otolith stimulation, as assessed by single unit recording from the vestibular nucleus in labyrinth-intact animals. These spatiotemporal features are also analyzed in association with other electrophysiological properties to evaluate their role in the central construction of a spatial frame of reference in the otolith system. Data derived from animals with elimination of inputs from one labyrinth then provide evidence that during vestibular stimulation signals arising from a single utricle are operative at the level of both the ipsilateral and contralateral vestibular nuclei. Hemilabyrinthectomy also revealed neural asymmetries in spontaneous activity, response dynamics and spatial coding behavior between neuronal subpopulations on the two sides and as a result suggested a segregation of otolith signals reaching the ipsilateral and contralateral vestibular nuclei. Recent studies have confirmed and extended previous observations that the recovery of resting activity within the vestibular nuclear complex during vestibular compensation is related to changes in both intrinsic membrane properties and capacities to respond to extracellular factors. The bilateral imbalance provides the basis for deranged spatial coding and motor deficits accompanying hemilabyrinthectomy. Taken together, these experimental findings indicate that in the normal state converging inputs from bilateral vestibular labyrinths are essential to spatiotemporal signal transformation at the central otolith neurons during low-frequency head movements.

Spatiotemporal Properties of Vestibular Responses in Area MSTd

“…Previous theoretical (Angelaki 1992(Angelaki , 1993bAngelaki et al 1992Angelaki et al , 1993 and neurophysiological (Angelaki and Dickman 2000;Chan et al 2002;Chen-Huang and Peterson 2006;Dickman and Angelaki 2002;Yakushin et al 2006) studies have proposed that VN neurons receive convergent inputs from otolith afferents that differ in both spatial and temporal properties. This convergence could include afferents from both labyrinths or across the striola within a given labyrinth (Uchino et al 2005).…”

Fos expression in otolith‐related brainstem neurons of postnatal rats following off‐vertical axis rotation

“…LV, lateral vestibular nucleus; MV, medial vestibular nucleus; SpV, spinal vestibular nucleus; SuV, superior vestibular nucleus; x, group x; y, group y. Chan et al, 2002). Because of its effectiveness for testing properties of the maculoocular reflex (Cohen et al, 1983;Hess and Dieringer, 1990), OVAR has also been taken as a convenient means for clinical assessment of utricular function (Furman et al, 1993).…”

Morphometric analysis of the AMPA-type neurons in the Deiters vestibular complex of the chick brain

“…The DC/vestibular lateral nucleus plays an important role coordinating the fine-tuning of postural control and ocular activities according to the movements of the head and body (Peusner, 2001;Chan et al, 2002). DC seems to be a relay station and many projections from the cerebellum areas as cortex, uvula, nodulus, and the flocculus terminate in the ipsilateral DC as well as efferent projections from the medial and intercalate nuclei (Wold, 1981).…”