Responses of Irregularly Discharging Chinchilla Semicircular Canal Vestibular-Nerve Afferents During High-Frequency Head Rotations

2005 ◽  
Vol 93 (5) ◽  
pp. 2777-2786 ◽  
Author(s):  
Timothy E. Hullar ◽  
Charles C. Della Santina ◽  
Timo Hirvonen ◽  
David M. Lasker ◽  
John P. Carey ◽  
...  
Keyword(s):  
Semicircular Canal ◽  
High Frequency ◽  
Peripheral Zone ◽  
High Gain ◽  
Vestibular Nerve ◽  
Head Movements ◽  
Response Dynamics ◽  
Stimulus Velocity ◽  
Vestibular Nerve Afferents ◽  
Irregular Afferents

Mammalian vestibular-nerve afferents innervating the semicircular canals have been divided into groups according to their discharge regularity, gain at 2-Hz rotational stimulation, and morphology. Low-gain irregular afferents terminate in calyx endings in the central crista, high-gain irregular afferents synapse more peripherally in dimorphic (bouton and calyx) endings, and regular afferents terminate in the peripheral zone as bouton-only and dimorphic endings. The response dynamics of these three groups have been described only up to 4 Hz in previous studies. Reported here are responses of chinchilla semicircular canal vestibular-nerve afferents to rotational stimuli at frequencies up to 16 Hz. The sensitivity of all afferents increased with increasing frequency with the sensitivity of low-gain irregular afferents increasing the most and matching the high-gain irregular afferents at 16 Hz. All afferents increased their phase lead with respect to stimulus velocity at higher frequencies with the highest leads in low-gain irregular afferents and the lowest in regular afferents. No attenuation of sensitivity or shift in phase consistent with the presence of a high-frequency pole over the range tested was noted. Responses were best fit with a torsion-pendulum model combined with a lead operator (τHF1s + 1)(τHF2s + 1). The discharge regularity of individual afferents was correlated to the value of each afferent's lead operator time constants. These findings suggest that low-gain irregular afferents are well suited for encoding the onset of rapid head movements, a property that would be advantageous for initiation of reflexes with short latency such as the vestibulo-ocular reflex.

Relationship of Semicircular Canal Size to Vestibular-Nerve Afferent Sensitivity in Mammals

2007 ◽  
Vol 98 (6) ◽  
pp. 3197-3205 ◽  
Author(s):  
Aizhen Yang ◽  
Timothy E. Hullar
Keyword(s):  
Semicircular Canal ◽  
High Frequency ◽  
High Gain ◽  
Vestibular Nerve ◽  
Radius Of Curvature ◽  
Horizontal Canal ◽  
Vestibular Nerve Afferents ◽  
The Relationship ◽  
Irregular Afferents ◽  
Anterior Canal

The relationship between semicircular canal radius of curvature and afferent sensitivity has not been experimentally determined. We characterized mouse semicircular canal afferent responses to sinusoidal head rotations to facilitate interspecies and intraspecies comparisons of canal size to sensitivity. The interspecies experiment compared the horizontal canal afferent responses among animals ranging in size from mouse to rhesus monkey. The intraspecies experiment compared afferent responses from the larger anterior canal to those from the smaller horizontal canal of mice. The responses of mouse vestibular-nerve afferents showed a low- and high-frequency phase lead and high-frequency gain enhancement. Regular horizontal-canal afferents showed a sensitivity to 0.5-Hz sinusoidal rotations of 0.10 ± 0.03 (SD) spike · s−1/deg · s−1 and high-gain irregular afferents showed a sensitivity of 0.25 ± 0.11 spike · s−1/deg · s−1. The interspecies comparison showed that the sensitivity of regular afferents was related to the radius of curvature R according to the formula Gr = 0.23R − 0.09 ( r2 = 0.86) and the sensitivity of irregular afferents was related to radius according to the formula Gi = 0.32R + 0.01 ( r2 = 0.67). The intraspecies comparison showed that regularly firing anterior canal afferents were significantly more sensitive than those from the relatively smaller horizontal canal, with Gr = 0.25R. This suggests that canal radius of curvature is closely related to afferent sensitivity both among and within species. If the relationship in humans is similar to that demonstrated here, the sensitivity of their regular vestibular-nerve afferents to 0.5-Hz rotations is likely to be about 0.67 spike · s−1/deg · s−1 and of their high-gain irregular afferents about 1.06 spikes · s−1/deg · s−1.

scholarly journals Response of Vestibular Nerve Afferents Innervating Utricle and Saccule During Passive and Active Translations

2009 ◽  
Vol 101 (1) ◽  
pp. 141-149 ◽  
Author(s):  
Mohsen Jamali ◽  
Soroush G. Sadeghi ◽  
Kathleen E. Cullen
Keyword(s):  
Efference Copy ◽  
Vestibular Nerve ◽  
Whole Body ◽  
Response Dynamics ◽  
Efferent System ◽  
Perceptual Stability ◽  
Vestibular Nerve Afferents ◽  
Otolith System ◽  
Head Translation ◽  
Passive Movements

The distinction between sensory inputs that are a consequence of our own actions from those that result from changes in the external world is essential for perceptual stability and accurate motor control. In this study, we investigated whether linear translations are encoded similarly during active and passive translations by the otolith system. Vestibular nerve afferents innervating the saccule or utricle were recorded in alert macaques. Single unit responses were compared during passive whole body, passive head-on-body, and active head-on-body translations (vertical, fore-aft, or lateral) to assess the relative influence of neck proprioceptive and efference copy-related signals on translational coding. The response dynamics of utricular and saccular afferents were comparable and similarly encoded head translation during passive whole body versus head-on-body translations. Furthermore, when monkeys produced active head-on-body translations with comparable dynamics, the responses of both regular and irregular afferents remained comparable to those recorded during passive movements. Our findings refute the proposal that neck proprioceptive and/or efference copy inputs coded by the efferent system function to modulate the responses of the otolith afferents during active movements. We conclude that the vestibular periphery provides faithful information about linear movements of the head in the space coordinates, regardless of whether they are self- or externally generated.

Response of Vestibular-Nerve Afferents to Active and Passive Rotations Under Normal Conditions and After Unilateral Labyrinthectomy

2007 ◽  
Vol 97 (2) ◽  
pp. 1503-1514 ◽  
Author(s):  
Soroush G. Sadeghi ◽  
Lloyd B. Minor ◽  
Kathleen E. Cullen
Keyword(s):  
Discharge Rate ◽  
Vestibular Nerve ◽  
The Body ◽  
Head Movements ◽  
Whole Body ◽  
Before And After ◽  
Unilateral Labyrinthectomy ◽  
Vestibular Nerve Afferents ◽  
Head Rotations

We investigated the possible contribution of signals carried by vestibular-nerve afferents to long-term processes of vestibular compensation after unilateral labyrinthectomy. Semicircular canal afferents were recorded from the contralesional nerve in three macaque monkeys before [horizontal (HC) = 67, anterior (AC) = 66, posterior (PC) = 50] and 1–12 mo after (HC = 192, AC = 86, PC = 57) lesion. Vestibular responses were evaluated using passive sinusoidal rotations with frequencies of 0.5–15 Hz (20–80°/s) and fast whole-body rotations reaching velocities of 500°/s. Sensitivities to nonvestibular inputs were tested by: 1) comparing responses during active and passive head movements, 2) rotating the body with the head held stationary to activate neck proprioceptors, and 3) encouraging head-restrained animals to attempt to make head movements that resulted in the production of neck torques of ≤2 Nm. Mean resting discharge rate before and after the lesion did not differ for the regular, D (dimorphic)-irregular, or C (calyx)-irregular afferents. In response to passive rotations, afferents showed no change in sensitivity and phase, inhibitory cutoff, and excitatory saturation after unilateral labyrinthectomy. Moreover, head sensitivities were similar during voluntary and passive head rotations and responses were not altered by neck proprioceptive or efference copy signals before or after the lesion. The only significant change was an increase in the proportion of C-irregular units postlesion, accompanied by a decrease in the proportion of regular afferents. Taken together, our findings show that changes in response properties of the vestibular afferent population are not likely to play a major role in the long-term changes associated with compensation after unilateral labyrinthectomy.

Analysis of afferent responses from isolated semicircular canal of the guitarfish using rotational acceleration white-noise inputs. I. Correlation of response dynamics with receptor innervation

1976 ◽  
Vol 39 (3) ◽  
pp. 631-644 ◽  
Author(s):  
D. P. O'Leary ◽  
R. F. Dunn
Keyword(s):  
White Noise ◽  
Semicircular Canal ◽  
Matched Filter ◽  
Dynamic Control ◽  
Head Movements ◽  
Rotational Acceleration ◽  
Response Dynamics ◽  
Response Characteristics ◽  
Cross Correlation Analysis ◽  
Nerve Bundles

The small-signal linear characteristics of afferent responses from the isolated semicircular canal were described by the use of white-noise rotational acceleration inputs. The results, based on cross-correlation analysis, showed a striking and systematic variation in linear system impulse response characteristics from afferents which innervated different regions of the receptor. Afferents from centrally located nerve bundles innervating the crest region of the crista exhibited an initial maximum response amplitude followed by a rapid decay. In contrast, afferents from extreme rostral and caudal nerve bundles innervating the crista slopes exhibited an initial rise up to a low-amplitude maximum followed by a slower decay.These results imply that the afferents innervating a single canal do not merely carry redundant information concerning current head acceleration, but could be considered an ensemble of specific classes of filters that are tuned individually to specific classes of head movements. On the basis of these considerations, a new hypothesis of matched filter detection was proposed as relevant to information processing and dynamic control in central vestibular pathways.

scholarly journals Effects of Canal Plugging on the Vestibuloocular Reflex and Vestibular Nerve Discharge During Passive and Active Head Rotations

2009 ◽  
Vol 102 (5) ◽  
pp. 2693-2703 ◽  
Author(s):  
Soroush G. Sadeghi ◽  
Jay M. Goldberg ◽  
Lloyd B. Minor ◽  
Kathleen E. Cullen
Keyword(s):  
Semicircular Canals ◽  
Vestibular Nerve ◽  
Head Movements ◽  
Vestibuloocular Reflex ◽  
Phase Lead ◽  
Afferent Discharge ◽  
Vestibular Nerve Afferents ◽  
Head Rotations ◽  
Central Adaptation ◽  
Nerve Discharge

Mechanical occlusion (plugging) of the slender ducts of semicircular canals has been used in the clinic as well as in basic vestibular research. Here, we investigated the effect of canal plugging in two macaque monkeys on the horizontal vestibuloocular reflex (VOR) and the responses of vestibular-nerve afferents during passive head rotations. Afferent responses to active head movements were also studied. The horizontal VOR gain decreased after plugging to <0.1 for frequencies <2 Hz but rose to about 0.6 as frequency was increased to 15 Hz. Afferents innervating plugged horizontal canals had response sensitivities that increased with the frequency of passive rotations from <0.01 (spikes/s)/(°/s) at 0.5 Hz to values of about 0.2 and 0.5 (spikes/s)/(°/s) at 8 Hz for regular and irregular afferents, respectively (<50% of responses in controls). An increase in phase lead was also noted following plugging in afferent discharge, but not in the VOR. Because the phase discrepancy between the VOR and afferent discharge is much larger than that seen in control animals, this suggests that central adaptation shapes VOR dynamics following plugging. The effect of canal plugging on afferent responses can be modeled as an increase in stiffness and a reduction in the dominant time constant and gain in the transfer function describing canal dynamics. Responses were also evident during active head rotations, consistent with the frequency content of these movements. We conclude that canal plugging in macaques is effective only at frequencies <2 Hz. At higher frequencies, afferents show significant responses, with a nearly 90° phase lead, such that they encode near-rotational acceleration. Our results demonstrate that afferents innervating plugged canals respond robustly during voluntary movements, a finding that has implications for understanding the effects of canal plugging in clinical practice.

A Broadband High-Gain Bi-Layer Log-Periodic Dipole Array (LPDA) for Ultra High Frequency (UHF) Conformal Load Bearing Antenna Structures (CLAS) Applications

2014 ◽  
Author(s):  
Nicholas A. Bishop ◽  
Mohammod Ali ◽  
Jason Miller ◽  
David L. Zeppettella ◽  
William Baron ◽  
...  
Keyword(s):  
High Frequency ◽  
High Gain ◽  
Load Bearing ◽  
Ultra High Frequency

Microearthquake seismicity and tectonics of Coastal Northern California

1970 ◽  
Vol 60 (5) ◽  
pp. 1669-1699 ◽  
Author(s):  
Leonardo Seeber ◽  
Muawia Barazangi ◽  
Ali Nowroozi
Keyword(s):  
High Frequency ◽  
Fault Plane ◽  
San Andreas Fault ◽  
High Gain ◽  
Strike Slip ◽  
Fault System ◽  
Northern California ◽  
Fault Plane Solutions ◽  
Sharp Bend ◽  
San Andreas

Abstract This paper demonstrates that high-gain, high-frequency portable seismographs operated for short intervals can provide unique data on the details of the current tectonic activity in a very small area. Five high-frequency, high-gain seismographs were operated at 25 sites along the coast of northern California during the summer of 1968. Eighty per cent of 160 microearthquakes located in the Cape Mendocino area occurred at depths between 15 and 35 km in a well-defined, horizontal seismic layer. These depths are significantly greater than those reported for other areas along the San Andreas fault system in California. Many of the earthquakes of the Cape Mendocino area occurred in sequences that have approximately the same magnitude versus length of faulting characteristics as other California earthquakes. Consistent first-motion directions are recorded from microearthquakes located within suitably chosen subdivisions of the active area. Composite fault plane solutions indicate that right-lateral movement prevails on strike-slip faults that radiate from Cape Mendocino northwest toward the Gorda basin. This is evidence that the Gorda basin is undergoing internal deformation. Inland, east of Cape Mendocino, a significant component of thrust faulting prevails for all the composite fault plane solutions. Thrusting is predominant in the fault plane solution of the June 26 1968 earthquake located along the Gorda escarpement. In general, the pattern of slip is consistent with a north-south crustal shortening. The Gorda escarpment, the Mattole River Valley, and the 1906 fault break northwest of Shelter Cove define a sharp bend that forms a possible connection between the Mendocino escarpment and the San Andreas fault. The distribution of hypocenters, relative travel times of P waves, and focal mechanisms strongly indicate that the above three features are surface expressions of an important structural boundary. The sharp bend in this boundary, which is concave toward the southwest, would tend to lock the dextral slip along the San Andreas fault and thus cause the regional north-south compression observed at Cape Mendocino. The above conclusions support the hypothesis that dextral strike-slip motion along the San Andreas fault is currently being taken up by slip along the Mendocino escarpment as well as by slip along northwest trending faults in the Gorda basin.

Inputs from regularly and irregularly discharging vestibular nerve afferents to secondary neurons in squirrel monkey vestibular nuclei. III. Correlation with vestibulospinal and vestibuloocular output pathways

1992 ◽  
Vol 68 (2) ◽  
pp. 471-484 ◽  
Author(s):  
R. Boyle ◽  
J. M. Goldberg ◽  
S. M. Highstein
Keyword(s):  
Spinal Cord ◽  
Transition Zone ◽  
Vestibular Nucleus ◽  
Vestibular Nuclei ◽  
Vestibular Nerve ◽  
Descending Pathways ◽  
Relative Contribution ◽  
Antidromic Stimulation ◽  
Vestibulospinal Tract ◽  
Irregular Afferents

1. A previous study measured the relative contributions made by regularly and irregularly discharging afferents to the monosynaptic vestibular nerve (Vi) input of individual secondary neurons located in and around the superior vestibular nucleus of barbiturate-anesthetized squirrel monkeys. Here, the analysis is extended to more caudal regions of the vestibular nuclei, which are a major source of both vestibuloocular and vestibulospinal pathways. As in the previous study, antidromic stimulation techniques are used to classify secondary neurons as oculomotor or spinal projecting. In addition, spinal-projecting neurons are distinguished by their descending pathways, their termination levels in the spinal cord, and their collateral projections to the IIIrd nucleus. 2. Monosynaptic excitatory postsynaptic potentials (EPSPs) were recorded intracellularly from secondary neurons as shocks of increasing strength were applied to Vi. Shocks were normalized in terms of the threshold (T) required to evoke field potentials in the vestibular nuclei. As shown previously, the relative contribution of irregular afferents to the total monosynaptic Vi input of each secondary neuron can be expressed as a %I index, the ratio (x100) of the relative sizes of the EPSPs evoked by shocks of 4 x T and 16 x T. 3. Antidromic stimulation was used to type secondary neurons as 1) medial vestibulospinal tract (MVST) cells projecting to spinal segments C1 or C6; 2) lateral vestibulospinal tract (LVST) cells projecting to C1, C6; or L1; 3) vestibulooculo-collic (VOC) cells projecting both to the IIIrd nucleus and by way of the MVST to C1 or C6; and 4) vestibuloocular (VOR) neurons projecting to the IIIrd nucleus but not to the spinal cord. Most of the neurons were located in the lateral vestibular nucleus (LV), including its dorsal (dLV) and ventral (vLV) divisions, and adjacent parts of the medial (MV) and descending nuclei (DV). Cells receiving quite different proportions of their direct inputs from regular and irregular afferents were intermingled in all regions explored. 4. LVST neurons are restricted to LV and DV and show a somatotopic organization. Those destined for the cervical and thoracic cord come from vLV, from a transition zone between vLV and DV, and to a lesser extent from dLV. Lumbar-projecting neurons are located more dorsally in dLV and more caudally in DV. MVST neurons reside in MV and in the vLV-DV transition zone.(ABSTRACT TRUNCATED AT 400 WORDS)

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