Planar Relationships of the Semicircular Canals in Two Strains of Mice

Calabrese, Daniel R.; Hullar, Timothy E.

doi:10.1007/s10162-006-0031-1

Cited by 65 publications

(76 citation statements)

References 48 publications

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“…Computations based upon our functional technique resulted in estimates of canal planes that were similar to the results from high-voltage X-ray computed tomography of the temporal bones (Calabrese and Hullar 2006).…”

Section: Geometry Of Canal Planesmentioning

confidence: 57%

Rotational Responses of Vestibular–Nerve Afferents Innervating the Semicircular Canals in the C57BL/6 Mouse

Lasker

Han

Park

et al. 2008

JARO

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Extracellular recordings were made from vestibularnerve afferents innervating the semicircular canals in anesthetized C57BL/6 mice ranging in age from 4-24 weeks. A normalized coefficient of variation was used to divide afferents into regular (CV*G0.1) and irregular (CV*90.1) groups. There were three overall conclusions from this study. First, mouse afferents resemble those of other mammals in properties such as resting discharge rate and dependence of response dynamics on discharge regularity. Second, there are differences in mouse afferents relative to other mammals that are likely related to the smaller size of the semicircular canals. The rotational sensitivity of mouse afferents is approximately threefold lower than that reported for afferents in other mammals. One consequence of the lower sensitivity is that mouse afferents have a larger linear range for encoding head velocity. The long time constant of afferent discharge, which is a measure of low-frequency response dynamics, is shorter in mouse afferents than in other species. Third, juvenile mice (age 4-7 weeks) appear to lack a class of low-sensitivity, highly irregular afferents that are present in adult animals (age 10-24 weeks). By analogy to studies in the chinchilla, these irregular afferents with low sensitivities for lower rotational frequencies correspond to calyx-only afferents. These findings suggest that, although the calyx ending on to type I hair cells is morphologically complete in mice by the age of about 1 month, the physiological response properties in these juvenile animals are not equivalent to those in adults.

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Section: Geometry Of Canal Planesmentioning

confidence: 57%

Rotational Responses of Vestibular–Nerve Afferents Innervating the Semicircular Canals in the C57BL/6 Mouse

Lasker

Han

Park

et al. 2008

JARO

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show abstract

“…Generally, amongst mammals, the anterior canal is larger than the posterior and lateral canals. This has been demonstrated in rats (Cummins, 1925), mice (Calabrese & Hullar, 2006), chinchillas (Hullar & Williams, 2006), little brown bats (Ramprashad et al 1980), rhesus and squirrel monkeys (Blanks et al 1985), as well as guinea pigs, cats and humans (Curthoys et al 1977). This relationship is also seen in most of the wide range of mammals studied by Ramprashad et al (1984) and the large number of primates examined by Spoor & Zonneveld (1998) although the anterior and posterior canals are often very close in size and, in some cases, the radius of the posterior canal exceeds that of the anterior canal (e.g.…”

Section: Canal Sizementioning

confidence: 67%

Semicircular canals and agility: the influence of size and shape measures

Cox

Jeffery

2009

Journal of Anatomy

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The semicircular canals of the inner ear sense angular accelerations and decelerations of the head and enable co-ordination of posture and body movement, as well as visual stability. Differences of agility and spatial sensitivity among species have been linked to interspecific differences in the relative size of the canals, particularly the radius of curvature (R) and the ratio of the canal plane area to streamline length (P ⁄ L). Here we investigate the scaling relationships of these two size variables and also out-of-plane torsion in the three semicircular canals (anterior, posterior and lateral), in order to assess which is more closely correlated with body size and locomotor agility. Measurements were computed from 3D landmarks taken from magnetic resonance images of a diverse sample of placental mammals encompassing 16 eutherian orders. Body masses were collected from the literature and an agility score was assigned to each species. The R and P ⁄ L of all three semicircular canals were found to have highly significant positive correlations with each other and no statistical difference was found between the slope of 2P ⁄ L against R and 1. This indicated that, contrary to initial hypotheses, there is little difference between 2P ⁄ L and R as measures of semicircular canal size. A measure of the in-plane circularity of the canal was obtained by dividing 2P ⁄ L by R and out-of-plane torsion was measured as angular deviation from a plane of best fit. It was predicted that deviations from in-plane and out-of-plane circularity would increase at small body size due to the constraints of fitting a proportionately larger canal into a smaller petrous bone. However, neither measurement was found to have a significant correlation with body mass, indicating that deviations from circularity (both in-plane and out-of-plane) are not sufficient to alter P ⁄ L to an extent that would impact the sensitivity of the canals. 2P ⁄ L and R were both shown to be significantly correlated with locomotor agility. The posterior canal was the least correlated with agility, suggesting that it may be generally less closely aligned to the direction of movement than the anterior canal. Of the three canals, the lateral canal was the most highly correlated with agility. In particular, it could be used to distinguish between species that move in a largely 2D environment and those that locomote in 3D space (aerial, arboreal and aquatic species). This complements previous work suggesting that the lateral canal primarily commands navigation, whereas the vertical canals control reflex adjustments. It was also found that 2P ⁄ L is substantially better correlated with agility than is R in the lateral canal. This result is intriguing given the above finding that there is no statistical difference between 2P ⁄ L and R, and requires further investigation.

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“…The angle of the horizontal semicircular canal is 23° upwards from L-B (Calabrese and Hullar, 2006), placing the canal during ambulation at 6° downwards from earthhorizontal. This value accords with the observation that most species position their heads so as to hold the plane of the horizontal semicircular canal horizontal.…”

Section: Natural Position Of the Head And The "Rest" Position Of The mentioning

confidence: 99%

“…It is also possible that the difference in horizontal canal inclination reflects the different mouse strains used in the two studies. The micro-CT study demonstrated significant inter-strain variation in the anatomic orientations of the semicircular canals (Calabrese and Hullar, 2006). Of particular significance, Vidal and colleagues studied the C3H strain.…”

Section: Natural Position Of the Head And The "Rest" Position Of The mentioning

confidence: 99%

Eye orientation during static tilts and its relationship to spontaneous head pitch in the laboratory mouse

Oommen

Stahl

2008

Brain Research

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Both eye position and head orientation are influenced by the macular (otolith) organs, via the tilt maculo-ocular reflex (tiltMOR) and the vestibulo-collic reflexes, respectively. The mechanisms that control head position also influence the rest position of the eye, because head orientation influences eye position through the tiltMOR. Despite the increasing popularity of mice for studies of vestibular and ocular motor functions, relatively little is known in this species about tiltMOR, spontaneous orientation of the head, and their interrelationship. We used 2D video oculography to determine in C57BL/6 mice the absolute horizontal and vertical positions of the eyes over body orientations spanning 360° about the pitch and roll axes. We also determined head pitch during ambulation in the same animals. Eye elevation varied approximately sinusoidally as functions of pitch or roll angle. Over the central ±30° of pitch, sensitivity and gain in the light were 31.7°/g and 0.53, respectively. The corresponding values for roll were 31.5°/g and 0.52. Absolute positions adopted in light and darkness differed only slightly. During ambulation, mice carried the lambda-bregma plane at a downward pitch of 29°, corresponding to a horizontal eye position of 64° and a vertical eye position of 22°. The vertical position is near the center of the range of eye movements produced by the pitch tiltMOR. The results indicate the tiltMOR is robust in this species, and favor standardizing pitch orientation across laboratories. The robust tiltMOR also has significant methodological implications for the practice of pupil-tracking video oculography in this species.

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Planar Relationships of the Semicircular Canals in Two Strains of Mice

Cited by 65 publications

References 48 publications

Rotational Responses of Vestibular–Nerve Afferents Innervating the Semicircular Canals in the C57BL/6 Mouse

Rotational Responses of Vestibular–Nerve Afferents Innervating the Semicircular Canals in the C57BL/6 Mouse

Semicircular canals and agility: the influence of size and shape measures

Eye orientation during static tilts and its relationship to spontaneous head pitch in the laboratory mouse

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