High-Frequency Dynamics of Regularly Discharging Canal Afferents Provide a Linear Signal for Angular Vestibuloocular Reflexes

1999 ◽  
Vol 82 (4) ◽  
pp. 2000-2005 ◽  
Author(s):  
Timothy E. Hullar ◽  
Lloyd B. Minor
Keyword(s):  
High Frequency ◽  
Harmonic Distortion ◽  
Semicircular Canals ◽  
Half Cycle ◽  
Phase Lead ◽  
Function Fitting ◽  
Linear Signal ◽  
Vestibular Nerve Afferents ◽  
Sinusoidal Rotations ◽  
Sensitivity Gain

Regularly discharging vestibular-nerve afferents innervating the semicircular canals were recorded extracellularly in anesthetized chinchillas undergoing high-frequency, high-velocity sinusoidal rotations. In the range from 2 to 20 Hz, with peak velocities of 151°/s at 6 Hz and 52°/s at 20 Hz, 67/70 (96%) maintained modulated discharge throughout the sinusoidal stimulus cycle without inhibitory cutoff or excitatory saturation. These afferents showed little harmonic distortion, no dependence of sensitivity on peak amplitude of stimulation, and no measurable half-cycle asymmetry. A transfer function fitting the data predicts no change in sensitivity (gain) of regularly discharging afferents over the frequencies tested but shows a phase lead with regard to head velocity increasing from 0° at 2 Hz to 30° at 20 Hz. These results indicate that regularly discharging afferents provide a plausible signal to drive the angular vestibuloocular reflex (VOR) even during high-frequency head motion but are not a likely source for nonlinearities present in the VOR.

Horizontal Vestibuloocular Reflex Evoked by High-Acceleration Rotations in the Squirrel Monkey. II. Responses After Canal Plugging

1999 ◽  
Vol 82 (3) ◽  
pp. 1271-1285 ◽  
Author(s):  
David M. Lasker ◽  
Douglas D. Backous ◽  
Anna Lysakowski ◽  
Griffin L. Davis ◽  
Lloyd B. Minor
Keyword(s):  
High Frequency ◽  
Peak Velocity ◽  
Vestibular Function ◽  
Semicircular Canals ◽  
Vestibuloocular Reflex ◽  
Half Cycle ◽  
High Acceleration ◽  
Linear And Nonlinear ◽  
Residual Response ◽  
Sinusoidal Rotations

The horizontal angular vestibuloocular reflex (VOR) evoked by high-frequency, high-acceleration rotations was studied in four squirrel monkeys after unilateral plugging of the three semicircular canals. During the period (1–4 days) that animals were kept in darkness after plugging, the gain during steps of acceleration (3,000°/s2, peak velocity = 150°/s) was 0.61 ± 0.14 (mean ± SD) for contralesional rotations and 0.33 ± 0.03 for ipsilesional rotations. Within 18–24 h after animals were returned to light, the VOR gain for contralesional rotations increased to 0.88 ± 0.05, whereas there was only a slight increase in the gain for ipsilesional rotations to 0.37 ± 0.07. A symmetrical increase in the gain measured at the plateau of head velocity was noted after animals were returned to light. The latency of the VOR was 8.2 ± 0.4 ms for ipsilesional and 7.1 ± 0.3 ms for contralesional rotations. The VOR evoked by sinusoidal rotations of 0.5–15 Hz, ±20°/s had no significant half-cycle asymmetries. The recovery of gain for these responses after plugging was greater at lower than at higher frequencies. Responses to rotations at higher velocities for frequencies ≥4 Hz showed an increase in contralesional half-cycle gain, whereas ipsilesional half-cycle gain was unchanged. A residual response that appeared to be canal and not otolith mediated was noted after plugging of all six semicircular canals. This response increased with frequency to reach a gain of 0.23 ± 0.03 at 15 Hz, resembling that predicted based on a reduction of the dominant time constant of the canal to 32 ms after plugging. A model incorporating linear and nonlinear pathways was used to simulate the data. The coefficients of this model were determined from data in animals with intact vestibular function. Selective increases in the gain for the linear and nonlinear pathways predicted the changes in recovery observed after canal plugging. An increase in gain of the linear pathway accounted for the recovery in VOR gain for both responses at the velocity plateau of the steps of acceleration and for the sinusoidal rotations at lower peak velocities. The increase in gain for contralesional responses to steps of acceleration and sinusoidal rotations at higher frequencies and velocities was due to an increase in the gain of the nonlinear pathway. This pathway was driven into inhibitory cutoff at low velocities and therefore made no contribution for rotations toward the ipsilesional side.

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.

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.

A design methodology for acoustic resonance-free, high-frequency, dimmable electronic ballast for high-pressure sodium-vapour lamps

2019 ◽  
Vol 52 (4) ◽  
pp. 524-539
Author(s):  
B Gupta Bakshi ◽  
B Roy
Keyword(s):  
High Pressure ◽  
High Frequency ◽  
Design Methodology ◽  
Power Level ◽  
Harmonic Distortion ◽  
Acoustic Resonance ◽  
Electrical Characteristics ◽  
Electronic Ballast ◽  
Lamp Current ◽  
Sodium Vapour

This paper presents a methodology to design acoustic resonance-free, high-frequency, dimmable electronic ballasts for high-pressure sodium vapour (HPSV) lamps having a range of rated wattage (70–400 W). After estimation of the ‘quiet window’ of an HPSV lamp, the proposed iterative algorithm is able to determine the acoustic resonance-free driving frequencies of a design ballast corresponding to 50%–100% power level. On the other hand, a developed wattage and voltage independent HPSV lamp model facilitates finding the required electrical characteristics of HPSV lamps without performing laboratory experimentation. Using the estimated driving frequencies of a design ballast and the synthesized electrical characteristics of the lamp, the design circuit parameters of an electronic ballast are determined. Performance evaluation of the designed ballasts, carried out on the Matlab–Simulink platform, indicates several important attributes, viz. higher power control accuracy (deviation ≤3.69%), near-unity lamp power factor (≥0.98), lower lamp current crest factor (<1.7) and lower lamp current total harmonic distortion (≤12.63%). Results establish the effectiveness of the proposed design methodology to design lightweight and compact electronic ballasts for HPSV lamps with less effort than conventional design practice.

scholarly journals Extremely High Frequency Resolution and Low Harmonic Distortion Digital Look-Up-Table Sinusoidal Oscillators

2000 ◽  
Vol 23 (2) ◽  
pp. 101-113 ◽  
Author(s):  
M. M. Al-Ibrahim (Jarrah)
Keyword(s):  
High Frequency ◽  
Harmonic Distortion ◽  
Frequency Resolution ◽  
Trigonometric Interpolation ◽  
New Techniques ◽  
Interpolation Methods ◽  
Sinusoidal Oscillators ◽  
Look Up Table ◽  
Extremely High Frequency ◽  
Address Register

New techniques to efficiently increase the frequency resolution of digital sinusoidal oscillators based on look-up-table (LUT) methods are proposed. The increase in frequency resolution is achieved while maintaining very low level of spurious harmonic distortion. The proposed techniques increase the LUT length to a level at which the spurious harmonic distortion is negligible. The first proposed technique is based on partitioning the address register into three sets and dividing the available LUT length into three smaller tables addressed according to the content of the address register sets. The second proposed technique utilizes one LUT and interpolates the values of the samples that are not stored in the table. The third proposed technique is similar to the first technique with the advantage of simpler implementation and lower levels of spurious harmonic distortion. The proposed techniques are simulated and their performance is compared with that of the direct LUT and trigonometric interpolation methods. The simulation results show that the proposed techniques are superior to both direct LUT and trigonometric interpolation methods.

Investigation and Improvement of Self-Oscillating Electronic Ballast for Local Fluorescent Emergency Light

2012 ◽  
Vol 614-615 ◽  
pp. 1539-1546
Author(s):  
Muhamad Fairus Hamid ◽  
Norazlan Hashim ◽  
Ahmad Farid Abidin
Keyword(s):  
High Frequency ◽  
Harmonic Distortion ◽  
Experimental Results ◽  
Total Harmonic Distortion ◽  
Switching Frequency ◽  
Switching Device ◽  
Electronic Ballast ◽  
Rectifier Circuit ◽  
Fluorescent Lamps

This paper presents an analysis and improvement of self-oscillation electronic ballast for local emergency light. The improvement circuit has been presented by replacing the original BJTs with MOSFETs as a switching device. Also, 555-timer has been used to drive the MOSFETs instead of the ballast feedback in the original circuit. This electronic ballast start and regulate fluorescent lamps by converting a DC supply to high ignition AC voltage by a rectifier circuit with switching frequency in the range of 20 kHz -1MHz. Operation at high frequency has two advantages; an improved efficiency and elimination of flickering in the lamps. The simulation has been done by using PSIM Simulink software and its results have been compared with experimental results. The results shows that by using MOSFETs as a switching device, the Total Harmonic Distortion (THD) has been reduced and the brightness of lamp tube has been increased greatly.

Harmonic Investigation and Simulation of Full Bridge LCL Resonant Inverter

2011 ◽  
Vol 403-408 ◽  
pp. 3600-3607
Author(s):  
S. Selvaperumal ◽  
C.Christober Asir Rajan
Keyword(s):  
Power Systems ◽  
High Frequency ◽  
Harmonic Distortion ◽  
Total Harmonic Distortion ◽  
Zero Voltage Switching ◽  
Resonant Inverter ◽  
Ac Power ◽  
Resistive Loads ◽  
Zero Voltage ◽  
Voltage Switching

This paper presents 250W, 20 KHz LCL resonant inverter having Efficiencies greater than 95% were obtained down to resistive loads of 50%. Efficiencies greater than 80% were obtained at significantly reduced loads (11%). Operation above resonance was utilized to increase the efficiency and maintain zero voltage switching (ZVS) for varied loads. Total harmonic distortion (THD) of less than 8% was achieved for all resistive loads. The above results were obtained from evaluation version of PSIM also used to model the LCL topology for varied loads and LCL configurations. A LCL Resonant Inverter is proposed for applications in high frequency distributed AC power systems.

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