Dimensional analysis and dynamic response characterization of mammalian peripheral vestibular structures

Ramprashad, Fred; Landolt, Jack P.; Money, K. E.; Laufer, Jerry

doi:10.1002/aja.1001690306

Cited by 35 publications

(24 citation statements)

References 38 publications

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“…The radius of curvature of the chinchilla semicircular canals have been previously determined to be 2.130 ± 0.168 mm for the anterior canal, 1.90 ± 0.015 for the horizontal canal, and 2.040 ± 0.306 mm for the posterior canal using histologic techniques (Ramprashad et al, 1984) These data agree well with the values reported here for the anterior and lateral canals, although the posterior canal radius reported here is somewhat smaller than previously described. The anterior canal is larger than the others in both studies, consistent with the relationship found in other species including pigeon (Landolt et al, 1975), bat (Ramprashad et al, 1980), guinea pig, squirrel and rhesus monkey (Blanks et al, 1985), and man (Curthoys et al, 1977).…”

Section: Shape Of Individual Canalssupporting

confidence: 81%

Geometry of the semicircular canals of the chinchilla (Chinchilla laniger)

Hullar

Williams

2006

Hearing Research

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The orientations of the semicircular canals determines the response of the canals to head rotations and, in turn, the brain's ability to interpret those motions. The geometry of chinchillas' semicircular canals has never been reported.Volumetric representations of three chinchilla skulls were generated using a microCT scanner. The centroids of each semicircular canal lumen were identified as they passed through the image slices and were regressed to a plane. Unit vectors normal to the plane representing canal orientations were used to calculate angles between canal pairs. Pitch and roll maneuvers required to bring any canal into the horizontal plane for physiologic investigation were calculated.The semicircular canals of the chinchilla were found to be relatively planar. The horizontal canal was found to be oriented 55.0° anteriorly upward. Pairs of ipsilateral chinchilla canals were not orthogonal and contralateral synergistic pairs were not parallel. Despite this arrangement, the canal plane unit normal vectors were organized to respond with approximately equal overall sensitivity to rotations in any direction. The nonorthogonal chinchilla labyrinth may provide an opportunity to determine whether the frame of reference used by the central vestibular and oculomotor system is based on directions of afferent maximum sensitivity or prime directions.

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Section: Shape Of Individual Canalssupporting

confidence: 81%

Geometry of the semicircular canals of the chinchilla (Chinchilla laniger)

Hullar

Williams

2006

Hearing Research

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“…Like the aVOR in all mammalian species examined so far (Ramprashad et al, 1984), mice exhibit a high-pass frequency response with respect to head rotational velocity, as shown in Figure 4. However, the mouse aVOR’s performance at different frequencies relative to other species is interesting, because it supports the notion that differences in aVOR gain and frequency dependence across species depend on static visual acuity.…”

Section: Discussionmentioning

confidence: 94%

Characterization of the 3D angular vestibulo-ocular reflex in C57BL6 mice

2010

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We characterized the three-dimensional angular vestibulo-ocular reflex (3D aVOR) of adult C57BL6 mice during static tilt testing, sinusoidal and high-acceleration rotations and compared it with that of another lateral-eyed mammal with afoveate retinae (chinchilla) and two primate species with forward eye orientation and retinal foveae (human and squirrel monkey). Noting that visual acuity in mice is poor compared to chinchillas and even worse compared to primates, we hypothesized that the mouse 3D aVOR would be relatively low in gain (eye-velocity/head-velocity) compared to other species and would fall off for combinations of head rotation velocity and frequency for which peak-to-peak position changes fall below the minimum visual angle resolvable by mice. We also predicted that as in chinchilla, the mouse 3D aVOR would be more isotropic (eye/head velocity gain independent of head rotation axis) and better aligned with the axis of head rotation than the 3D aVOR of primates. In 12 adult C57BL6 mice, binocular 3D eye movements were measured in darkness during whole-body static tilts, 20-100°/s whole-body sinusoidal rotations (0.02-10 Hz) and acceleration steps of 3000°/s2 to a 150°/s plateau (dominant spectral content 8-12 Hz). Our results show that the mouse has a robust static tilt counter-roll response gain of ~0.35 (eye-position Δ / head-position Δ) and mid-frequency aVOR gain (~0.6-0.8), but relatively low aVOR gain for high frequency sinusoidal head rotations and for steps of head rotation acceleration (~0.5). Due to comparatively poor static visual acuity in the mouse, a perfectly compensatory 3D aVOR would confer relatively little benefit during high-frequency, low amplitude movements. Therefore our data suggest that the adaptive drive for maintaining a compensatory 3D aVOR depends on the static visual acuity in different species. Like chinchillas, mice have a much more nearly isotropic 3D aVOR than do the primates for which comparable data are available. Relatively greater isotropy in lateral-eyed species without retinal foveae (e.g., mice and chinchillas in the present study) compared to forward-eyed species with retinal foveae (e.g., squirrel monkeys and humans) suggests that the parallel resting optic axes and/or radially symmetric retinal foveae of primates underlie their characteristically low 3D aVOR gain for roll head rotations.

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“…Because the separation between different vestibular nerve branches in the rhesus labyrinth is ∼1.5-1.7 times greater in rhesus than in chinchillas (Ramprashad et al 1984), we hypothesized that rhesus monkeys would exhibit findings at least as close to normal as those we have observed in chinchillas. Furthermore, even though elevated baseline stimulation with co-modulation and alignment precompensation strategies have both been shown to improve eye responses when employed separately, we sought to determine the eye response effects of simultaneously adapting the animal to elevated baseline stimulation and delivering comodulated stimuli with alignment precompensation.…”

Section: Introductionmentioning

confidence: 85%

Multichannel Vestibular Prosthesis Employing Modulation of Pulse Rate and Current with Alignment Precompensation Elicits Improved VOR Performance in Monkeys

Davidovics

Rahman

Dai

et al. 2013

JARO

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An implantable prosthesis that stimulates vestibular nerve branches to restore the sensation of head rotation and the three-dimensional (3D) vestibular ocular reflex (VOR) could benefit individuals disabled by bilateral loss of vestibular sensation. Our group has developed a vestibular prosthesis that partly restores normal function in animals by delivering biphasic current pulses via electrodes implanted in semicircular canals. Despite otherwise promising results, this approach has been limited by insufficient velocity of VOR response to head movements that should inhibit the implanted labyrinth and by misalignment between direction of head motion and prosthetically elicited VOR. We report that significantly larger VOR eye velocities in the inhibitory direction can be elicited by adapting a monkey to elevated baseline stimulation rate and current prior to stimulus modulation and then concurrently modulating ("co-modulating") both rate and current below baseline levels to encode inhibitory angular head velocity. Comodulation of pulse rate and current amplitude above baseline can also elicit larger VOR eye responses in the excitatory direction than do either pulse rate modulation or current modulation alone. Combining these stimulation strategies with a precompensatory 3D coordinate transformation improves alignment and magnitude of evoked VOR eye responses. By demonstrating that a combination of co-modulation and precompensatory transformation strategies achieves a robust VOR response in all directions with significantly improved alignment in an animal model that closely resembles humans with vestibular loss, these findings provide a solid preclinical foundation for application of vestibular stimulation in humans.

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Dimensional analysis and dynamic response characterization of mammalian peripheral vestibular structures

Cited by 35 publications

References 38 publications

Geometry of the semicircular canals of the chinchilla (Chinchilla laniger)

Geometry of the semicircular canals of the chinchilla (Chinchilla laniger)

Characterization of the 3D angular vestibulo-ocular reflex in C57BL6 mice

Multichannel Vestibular Prosthesis Employing Modulation of Pulse Rate and Current with Alignment Precompensation Elicits Improved VOR Performance in Monkeys

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