Journal of Vestibular Research - Volume 7, issue 5

Authors: Allison, R.S. | Eizenman, M. | Tomlinson, R.D. | Nedzelski, J. | Sharpe, J.A.

Article Type: Research Article

Abstract: The response of the vestibulo-ocular reflex following unilateral vestibular deafferentation by gentamicin ablation was studied using transient stimuli. The response to these rapid passive head turns showed a strong asymmetry with permanent, reduced gains toward the side of lesion. These gain reductions have large variation (gains of 0.26 to 0.83), which may result from preferential sparing of regularly firing afferent fibers following gentamicin ablation. Based on the size and nature of the nonlinearity, an explanation based on Ewald’s second law was discounted.

Keywords: vestibular, vestibulo-ocular reflex, ototoxic, Ménière’s, gentamicin

DOI: 10.3233/VES-1997-7501

Citation: Journal of Vestibular Research, vol. 7, no. 5, pp. 369-380, 1997

Authors: DiZio, Paul | Li, Wenxun | Lackner, James R. | Matin, Leonard

Article Type: Research Article

Abstract: Psychophysical measurements of the level at which observers set a small visual target so as to appear at eye level (VPEL) were made on 13 subjects in 1.0 g and 1.5 g environments in the Graybiel Laboratory rotating room while they viewed a pitched visual field or while in total darkness. The gravitoinertial force was parallel to the z-axis of the head and body during the measurements. The visual field consisted of two 58° high, luminous, pitched-from-vertical, bilaterally symmetric, parallel lines, viewed in otherwise total darkness. The lines were horizontally separated by 53° and presented at each of 7 angles of pitch …ranging from 30° with the top of the visual field turned away from the subject (top backward) to 30° with the top turned toward the subject (top forward). At 1.5 g, VPEL changed linearly with the pitch of the 2-line stimulus and was depressed with top hackward pitch and elevated with top forward pitch as had been reported previously at 1.0 g (1.2): however, the slopes of the VPEL-vs-pitch functions at 1.0 g and 1.5 g were indistinguishable. As reported previously also (3,4), the VPEL in darkness was considerably lower at 1.5 g than at 1.0 g: however, although the y-intercept of the VPEL-vs-pitch function in the presence of the 2-line visual field (visual field erect) was also lower at 1.5 g than at 1.0 g as it was in darkness, the G-related difference was significantly attenuated by the presence of the visual field. The quantitative characteristics of the results are consistent with a model in which VPEL is treated as a consequence of an algebraic weighted average or a vector sum of visual and nonvisual influences although the two combining rules lead to fits that are equally good. Show more

Keywords: eye level, visual localization, visual field, gravitoinertial force, sensorimotor integration, spatial orientation, human

DOI: 10.3233/VES-1997-7502

Citation: Journal of Vestibular Research, vol. 7, no. 5, pp. 381-392, 1997

Authors: Ricci, Anthony J. | Rennie, Katherine J. | Cochran, Stephen L. | Kevetter, Golda A. | Correia, Manning J.

Article Type: Research Article

Abstract: Classically, type I and type II vestibular hair cells have been defined by their afferent innervation patterns. Little quantitative information exists on the intrinsic morphometric differences between hair cell types. Data presented here define a quantitative method for distinguishing hair cell types based on the morphometric properties of the hair cell’s neck region. The method is based initially on fixed histological sections, where hair cell types were identified by innervation pattern, type I cells having an afferent calyx. Cells were viewed using light microscopy, images were digitized, and measurements were made of the cell body width, the cuticular plate width, …and the neck width. A plot of the ratio of the neck width to cuticular plate width (NPR) versus the ratio of the neck width to the body width (NBR) established four quadrants based on the best separation of type I and type II hair cells. The combination of the two variables made the accuracy of predicting either type I or type II hair cells greater than 90%. Statistical cluster analysis confirmed the quadrant separation. Similar analysis was performed on dissociated hair cells from semicircular canal, utricle, and lagena, giving results statistically similar to those of the fixed tissue. Additional comparisons were made between fixed tissue and isolated hair cells as well as across species (pigeon and gerbil) and between end organs (semicircular canal, utricle, and lagena). In each case, the same morphometric boundaries could be used to establish four quadrants, where quadrant 1 was predominantly type I cells and quadrant 3 was almost exclusively type II hair cells. The quadrant separations were confirmed statistically by cluster analysis. These data demonstrate that there are intrinsic morphometric differences between type I and type II hair cells and that these differences can be maintained when the hair cells are dissociated from their respective epithelia. Show more

Keywords: vestibular system, hair cells, morphology, inner ear, labyrinth

DOI: 10.3233/VES-1997-7503

Citation: Journal of Vestibular Research, vol. 7, no. 5, pp. 393-406, 1997

Authors: Ricci, Anthony J. | Cochran, Stephen L. | Rennie, Katherine J. | Correia, Manning J.

Article Type: Research Article

Abstract: Morphometric properties of solitary hair cells dissociated from the semicircular canals (SCC), utricles (UTR), and lagenas (LAG) of adult white king pigeons, Columba livia, were compared. Measurements were made of the cell body, cuticular plate and hair bundle. Cells were divided into two groups: type 1 (group 1) was predominantly type I hair cells, and type 2 (group 3) was primarily type II hair cells. Comparisons are made initially between end organs for each group. A subpopulation of short otolith hair cells was identified. Quantitative comparisons between isolated type 1 and type 2 hair cells demonstrated that type 1 hair …cells were more homogeneous both within and between vestibular end organs; while they had shorter, thinner neck regions, narrower apical surfaces, with longer and thinner bodies than did type 2 hair cells. Generally, for both type 1 and type 2 hair cells, two different hair bundle shapes were present, those (unimodal) with a single sharp taper from longest to shortest stereocilia, and those (bimodal) with an initial steep tape-followed by a less steep taper. An additional subtype of type 1 hair cells with short hair bundles was identified. SCC hair cells have fewer hair bundles with bimodal tapers across all cell groups when compared to UTR or LAG. All cell subtypes identified for dissociated hair cells were corroborated using histologic sections. Show more

Keywords: hair cells, semicircular canal, utricle, lagena, morphology

DOI: 10.3233/VES-1997-7504

Citation: Journal of Vestibular Research, vol. 7, no. 5, pp. 407-420, 1997