scholarly journals Optokinetic Responses, Visual Adaptation and Multisensory Control of Eye Movements in the Spiny Lobster, Palinurus Vulgaris

1983 ◽  
Vol 107 (1) ◽  
pp. 349-366 ◽  
Author(s):  
D.M. NEIL ◽  
H. SCHÖNE ◽  
F. SCAPINI ◽  
J.A. MIYAN
Keyword(s):  
Eye Movements ◽  
Spiny Lobster ◽  
Low Frequency ◽  
Frequency Range ◽  
Previous Response ◽  
Optokinetic Response ◽  
Response Level ◽  
Low Frequencies ◽  
Optokinetic Responses ◽  
Proprioceptive Inputs

1. The optokinetic responses of the spiny lobster, Palinurus vulgaris, were measured in the vertical roll plane. The eyes followed the stripes without nystagmus, and demonstrated incomplete bilateral coupling. Closed-loop responses to oscillating stripes (20° peak-to-peak) showed marked habituation at frequencies above 0.1 Hz, but at lower frequencies continued undiminished, with amplitude-gain values approaching 1.0. 2. Changes in illuminance level demonstrated that the optokinetic response exhibited a threshold below which the eye initially failed to detect and follow the stripes. However, over a period of several minutes, the previous response level could be restored or even exceeded. 3. The optokinetic response could be antagonized by a response to the irradiance gradient, which also had a threshold and showed adaptation. Migration of visual screening pigments may underlie these adaptation processes. 4. Optokinetic stimuli could interact with proprioceptive inputs arising from displacements of the legs on a moving platform. When the proprioceptive inputs were of equal frequency and in antiphase, the optokinetic response was reduced in amplitude; it was in phase with the visual stimulus at low frequencies, and in phase with the platform in the high-frequency range. When the inputs had unequal frequencies, the eyes followed the drum if its frequency was low, but failed to follow either drum or platform if drum frequency was high. We conclude that multisensory control extends the frequency range of operation of compensatory eye movements, and is dominated by the low-frequency optokinetic response.

Adaptation and other Phenomena in the Optokinetic Response of the Crab, Carcinus

1966 ◽  
Vol 44 (2) ◽  
pp. 285-295
Author(s):  
G. A. HORRIDGE
Keyword(s):  
Eye Movements ◽  
Vertical Plane ◽  
Low Frequency ◽  
Inhibitory Effect ◽  
Two Dimensions ◽  
Temporary Increase ◽  
Optokinetic Response ◽  
Optokinetic Responses ◽  
Visual Stabilization ◽  
Frequency Components

1. Adaptation to oscillatory stimuli is significant in the range 1-10/sec., for angular amplitudes of about 1°. The mechanism for perception of slow components remains unchanged when that to fast components is eliminated by adaptation. 2. Spontaneous leg movements are accompanied by a temporary increase in gain, showing a central control of the gain. 3. All eye movements are in two dimensions and components in the vertical plane appear similar to those in the horizontal plane, except that in the vertical plane the maximum range is over about 5° and there is no fast return phase. 4. The eye position is less stable in the dark. A single small light giving 0.0003 lux is sufficient to remove low-frequency components from the spontaneous eye movements 5. An imposed tremor of amplitude 0.2-2.0° and period 1-10 sec. is sufficient to make stationary stripes, which would otherwise be ineffective, have an inhibitory effect on movements of the other eye. 6. A new form of arthropod eye movement, saccadic flicks, can be a sign of arousal and attention. 7. Optokinetic responses are a consequence of the visual stabilization of the eye.

Otolith Deprivation Induces Optokinetic Compensation

2005 ◽  
Vol 94 (5) ◽  
pp. 3487-3496 ◽  
Author(s):  
Corina E. Andreescu ◽  
Martijn M. De Ruiter ◽  
Chris I. De Zeeuw ◽  
Marcel T. G. De Jeu
Keyword(s):  
Eye Movements ◽  
Multisensory Integration ◽  
Stimulus Frequency ◽  
Low Frequency ◽  
Integration Theory ◽  
Otolith Organs ◽  
Frequency Range ◽  
Optokinetic Reflex ◽  
Proprioceptive Inputs ◽  
Model Support

According to the multisensory integration theory vestibular, optokinetic and proprioceptive inputs act in concert to maintain a stable retinal image of the visual world. Yet, it remains elusive to what extent the otolith organs contribute to this process and whether a specific loss of otolith input is compensated for. Here we investigated the compensatory eye movements in tilted mice, which lack otoconia because of a mutation in otopetrin 1. Tilted mice showed very small displacements of the eyes in the orbit during static roll paradigms, suggesting the absence of functional otolith organs. Independent of head position with respect to gravity, the gain and phase lead of angular vestibuloocular reflex of tilted mice were decreased and increased, respectively (frequencies 0.2 to 1 Hz and peak accelerations 8 to 197°/s2, respectively). Furthermore, lack of otolith input increases the dependency of the vestibular system on stimulus frequency. In contrast, the gain of optokinetic reflex in tilted mice was significantly higher in the low-frequency range than in control mice, regardless of the position of the mice in space or the plane of the eye movements. To explain these results, a simple model was used in which a multisensory integration unit was embedded. With this model, we were able to simulate all the behaviors observed. Thus our data and the model support the presence of the multisensory integration system and revealed a compensatory enhanced optokinetic reflex in tilted mice, indicating an adaptive synergism in the processing of otolith and visually driven signals.

A waveform inversion technique for measuring elastic wave attenuation in cylindrical bars

Geophysics ◽  
1992 ◽  
Vol 57 (6) ◽  
pp. 854-859 ◽  
Author(s):  
Xiao Ming Tang
Keyword(s):  
Elastic Wave ◽  
Wave Attenuation ◽  
Waveform Inversion ◽  
Finite Size ◽  
Low Frequency ◽  
Frequency Range ◽  
Multiple Reflections ◽  
Low Frequencies ◽  
The Time Domain ◽  
Attenuation Values

A new technique for measuring elastic wave attenuation in the frequency range of 10–150 kHz consists of measuring low‐frequency waveforms using two cylindrical bars of the same material but of different lengths. The attenuation is obtained through two steps. In the first, the waveform measured within the shorter bar is propagated to the length of the longer bar, and the distortion of the waveform due to the dispersion effect of the cylindrical waveguide is compensated. The second step is the inversion for the attenuation or Q of the bar material by minimizing the difference between the waveform propagated from the shorter bar and the waveform measured within the longer bar. The waveform inversion is performed in the time domain, and the waveforms can be appropriately truncated to avoid multiple reflections due to the finite size of the (shorter) sample, allowing attenuation to be measured at long wavelengths or low frequencies. The frequency range in which this technique operates fills the gap between the resonant bar measurement (∼10 kHz) and ultrasonic measurement (∼100–1000 kHz). By using the technique, attenuation values in a PVC (a highly attenuative) material and in Sierra White granite were measured in the frequency range of 40–140 kHz. The obtained attenuation values for the two materials are found to be reliable and consistent.

Optimally Sensitive and Efficient Compact Loudspeakers for Low Audio Frequencies

2007 ◽  
Vol 38 (7) ◽  
pp. 11-17
Author(s):  
Ronald M. Aarts
Keyword(s):  
Optimality Criterion ◽  
Low Frequency ◽  
Audio Signal ◽  
Design Procedure ◽  
Frequency Range ◽  
Force Factor ◽  
Low Frequencies ◽  
Limited Frequency ◽  
The Cost ◽  
Higher Sensitivity

Conventionally, the ultimate goal in loudspeaker design has been to obtain a flat frequency response over a specified frequency range. This can be achieved by carefully selecting the main loudspeaker parameters such as the enclosure volume, the cone diameter, the moving mass and the very crucial “force factor”. For loudspeakers in small cabinets the results of this design procedure appear to be quite inefficient, especially at low frequencies. This paper describes a new solution to this problem. It consists of the combination of a highly non-linear preprocessing of the audio signal and the use of a so called low-force-factor loudspeaker. This combination yields a strongly increased efficiency, at least over a limited frequency range, at the cost of a somewhat altered sound quality. An analytically tractable optimality criterion has been defined and has been verified by the design of an experimental loudspeaker. This has a much higher efficiency and a higher sensitivity than current low-frequency loudspeakers, while its cabinet can be much smaller.

scholarly journals A census of the pulsar population observed with the international LOFAR station FR606 at low frequencies (25–80 MHz)

2020 ◽  
Vol 635 ◽  
pp. A76 ◽  
Author(s):  
L. Bondonneau ◽  
J.-M. Grießmeier ◽  
G. Theureau ◽  
A. V. Bilous ◽  
V. I. Kondratiev ◽  
...  
Keyword(s):  
Low Frequency ◽  
Frequency Range ◽  
Radio Pulsars ◽  
Low Frequencies ◽  
Radio Observatory ◽  
Future Studies ◽  
New Information ◽  
Upper Limits ◽  
Widespread Phenomenon ◽  
First Time

Context. To date, only 69 pulsars have been identified with a detected pulsed radio emission below 100 MHz. A LOFAR-core LBA census and a dedicated campaign with the Nançay LOFAR station in stand-alone mode were carried out in the years 2014–2017 in order to extend the known population in this frequency range. Aims. In this paper, we aim to extend the sample of known radio pulsars at low frequencies and to produce a catalogue in the frequency range of 25–80 MHz. This will allow future studies to probe the local Galactic pulsar population, in addition to helping explain their emission mechanism, better characterising the low-frequency turnover in their spectra, and obtaining new information about the interstellar medium through the study of dispersion, scattering, and scintillation. Methods. We observed 102 pulsars that are known to emit radio pulses below 200 MHz and with declination above −30°. We used the Low Band Antennas (LBA) of the LOw Frequency ARray (LOFAR) international station FR606 at the Nançay Radio Observatory in stand-alone mode, recording data between 25 and 80 MHz. Results. Out of our sample of 102 pulsars, we detected 64. We confirmed the existence of ten pulsars detected below 100 MHz by the LOFAR LBA census for the first time (Bilous et al. 2020, A&A, 635, A75) and we added two more pulsars that had never before been detected in this frequency range. We provided average pulse profiles, DM values, and mean flux densities (or upper limits in the case of non-detections). The comparison with previously published results allows us to identify a hitherto unknown spectral turnover for five pulsars, confirming the expectation that spectral turnovers are a widespread phenomenon.

Low Frequency Absorption of Additively Manufactured Cylinders

2019 ◽  
Author(s):  
Sophie R. Kaye ◽  
Ethan D. Casavant ◽  
Paul E. Slaboch
Keyword(s):  
Low Frequency ◽  
Normal Incidence ◽  
Frequency Noise ◽  
Outer Diameter ◽  
Acoustic Absorption ◽  
Frequency Range ◽  
Large Space ◽  
Low Frequencies ◽  
Cylinder Length ◽  
Hollow Cylinders

Abstract Attenuating low frequencies is often problematic, due to the large space required for common absorptive materials to mitigate such noise. However, natural hollow reeds are known to effectively attenuate low frequencies while occupying relatively little space compared to traditional absorptive materials. This paper discusses the effect of varied outer diameter, and outer spacing on the 200–1600 Hz acoustic absorption of additively manufactured arrays of hollow cylinders. Samples were tested in a 10 cm diameter normal incidence impedance tube such that cylinder length was oriented perpendicular to the incoming plane wave. By varying only one geometric element of each array, the absorption due to any particular parameter can be assessed individually. The tests confirmed the hypothesis that minimizing cylinder spacing and maximizing cylinder diameter resulted in increased overall absorption and produced more focused absorption peaks at specific low frequencies. Wider cylinder spacing produced a broader absorptive frequency range, despite shifting upward in frequency. Thus, manipulating these variables can specifically target absorption for low frequency noise that would otherwise disturb listeners.

Far infrared spectra and vibrational assignments of substituted benzenes

1967 ◽  
Vol 298 (1452) ◽  
pp. 51-63 ◽  
Keyword(s):  
Low Temperature ◽  
Low Frequency ◽  
Far Infrared ◽  
Marked Variation ◽  
Frequency Range ◽  
Substituted Benzenes ◽  
Low Frequencies ◽  
Vibrational Assignments ◽  
Bending Mode ◽  
Far Infrared Spectra

The vibrational absorption spectra of some substituted benzenes have been measured in the range 50 to 450 cm -1 . The compounds were measured as liquids, in solutions, as crystalline solidsat low temperature, and in polyethylene matrices. The extension of the infrared spectrum to very low frequencies has made it possible to determine new values for many fundamental vibrations. An assignment of all the vibrational frequencies in the low-frequency range has been made, from the infrared and Raman data, for p -dihalogeno-benzenes, p -halogenotoluenes, p -halogeno-nitrobenzenes, and for some mono-substituted benzenes. Some measurements have been made on the marked variation of intensity of the lowest frequency bending mode of p -dihalogeno-benzenes.

Response selectivity for multiple dimensions of frequency sweeps in the pallid bat inferior colliculus

1994 ◽  
Vol 72 (3) ◽  
pp. 1061-1079 ◽  
Author(s):  
Z. M. Fuzessery
Keyword(s):  
Inferior Colliculus ◽  
High Frequency ◽  
Low Frequency ◽  
Central Nucleus ◽  
Frequency Change ◽  
Frequency Range ◽  
Low Frequencies ◽  
Response Properties ◽  
Sweep Direction ◽  
Pallid Bat

1. While hunting, the pallid bat uses passive sound localization at low frequencies to find terrestrial prey, and echolocation for general orientation. It must therefore process two different types of acoustic input at the same time. The pallid bat's echolocation pulse is a downward frequency-modulated (FM) sweep from 60 to 30 kHz. This study examined the response selectivity of single neurons in the pallid bat's central nucleus of the inferior colliculus (ICC) for FM sweeps, comparing the response properties of the high-frequency population, tuned to the biosonar pulse, with the low-frequency population, tuned below the pulse. The working hypothesis was that the high-frequency population would exhibit a response selectivity for downward FM sweeps that was not present in the low-frequency population. 2. Neurons were tested for their selectivity for FM sweep direction, duration, frequency range and bandwidth, and rate of frequency change. The extent to which they responded exclusively to tones, noise, and FM sweeps was also examined. Significant differences in the response properties of neurons in the two populations were found. In the low-frequency population, all neurons responded to tones, but only 50% responded to FM sweeps. Only 23% were selective for sweep direction. In the high-frequency population, all neurons responded to FM sweeps, but 31% did not respond to tones. Over one-half of this population was selective for sweep direction, and of those that were selective, all preferred the downward sweep direction of the biosonar pulse. A large percentage (31%) responded exclusively to downward sweeps, and not to tones or upward sweeps. None of the cells in either population responded to noise, or did so only at very high relative thresholds. 3. Both populations contained neurons that were selective for short stimulus durations that approximated the duration of the biosonar pulse, although the percentage was greater in the high-frequency population (58% vs. 20%). In the high-frequency population, 31% of the neurons tested for duration responded exclusively to both the sweep direction and duration of the biosonar pulse. 4. Downward FM-selective neurons, with one exception, were generally insensitive to the rate of frequency change of the FM sweep, as well as the frequency range and bandwidth of the sweep. They responded similarly to both the full 60- to 30-kHz sweep and to 5-kHz bandwidth portions of the full sweep.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Comparison of optomotor and optokinetic reflexes in mice

2017 ◽  
Vol 118 (1) ◽  
pp. 300-316 ◽  
Author(s):  
Friedrich Kretschmer ◽  
Momina Tariq ◽  
Walid Chatila ◽  
Beverly Wu ◽  
Tudor Constantin Badea
Keyword(s):  
Eye Movements ◽  
Retinal Ganglion Cells ◽  
Ganglion Cells ◽  
Head Movements ◽  
Retinal Ganglion ◽  
Optomotor Response ◽  
Optokinetic Response ◽  
Stimulus Velocity ◽  
Image Stabilization ◽  
Optokinetic Responses

During animal locomotion or position adjustments, the visual system uses image stabilization reflexes to compensate for global shifts in the visual scene. These reflexes elicit compensatory head movements (optomotor response, OMR) in unrestrained animals or compensatory eye movements (optokinetic response, OKR) in head-fixed or unrestrained animals exposed to globally rotating striped patterns. In mice, OMR are relatively easy to observe and find broad use in the rapid evaluation of visual function. OKR determinations are more involved experimentally but yield more stereotypical, easily quantifiable results. The relative contributions of head and eye movements to image stabilization in mice have not been investigated. We are using newly developed software and apparatus to accurately quantitate mouse head movements during OMR, quantitate eye movements during OKR, and determine eye movements in freely behaving mice. We provide the first direct comparison of OMR and OKR gains (head or eye velocity/stimulus velocity) and find that the two reflexes have comparable dependencies on stimulus luminance, contrast, spatial frequency, and velocity. OMR and OKR are similarly affected in genetically modified mice with defects in retinal ganglion cells (RGC) compared with wild-type, suggesting they are driven by the same sensory input (RGC type). OKR eye movements have much higher gains than the OMR head movements, but neither can fully compensate global visual shifts. However, combined eye and head movements can be detected in unrestrained mice performing OMR, suggesting they can cooperate to achieve image stabilization, as previously described for other species. NEW & NOTEWORTHY We provide the first quantitation of head gain during optomotor response in mice and show that optomotor and optokinetic responses have similar psychometric curves. Head gains are far smaller than eye gains. Unrestrained mice combine head and eye movements to respond to visual stimuli, and both monocular and binocular fields are used during optokinetic responses. Mouse OMR and OKR movements are heterogeneous under optimal and suboptimal stimulation and are affected in mice lacking ON direction-selective retinal ganglion cells.

Empirical and theoretical analysis of the extremely low frequency arterial blood pressure power spectrum in unanesthetized rat

2006 ◽  
Vol 291 (6) ◽  
pp. H2816-H2824 ◽  
Author(s):  
David R. Brown ◽  
Lisa A. Cassis ◽  
Dennis L. Silcox ◽  
Laura V. Brown ◽  
David C. Randall
Keyword(s):  
Blood Pressure ◽  
Time Series ◽  
Power Spectrum ◽  
Arterial Blood Pressure ◽  
Low Frequency ◽  
Absolute Difference ◽  
Frequency Range ◽  
Low Frequencies ◽  
Extremely Low Frequency ◽  
Arterial Blood

The slope of the log of power versus the log of frequency in the arterial blood pressure (BP) power spectrum is classically considered constant over the low-frequency range (i.e., “fractal” behavior), and is quantified by β in the relationship “1/ fβ.” In practice, the fractal range cannot extend to indefinitely low frequencies, but factor(s) that terminate this behavior, and determine β, are unclear. We present 1) data in rats ( n = 8) that reveal an extremely low frequency spectral region (0.083–1 cycle/h), where β approaches 0 (i.e., the “shoulder”); and 2) a model that 1) predicts realistic values of β within that range of the spectrum that conforms to fractal dynamics (∼1–60 cycles/h), 2) offers an explanation for the shoulder, and 3) predicts that the “successive difference” in mean BP (mBP) is an important parameter of circulatory function. We recorded BP for up to 16 days. The absolute difference between successive mBP samples at 0.1 Hz (the successive difference, or Δ) was 1.87 ± 0.21 mmHg (means ± SD). We calculated β for three frequency ranges: 1) 0.083–1; 2) 1–6; and 3) 6–60 cycles/h. The β for all three regions differed ( P < 0.01). For the two higher frequency ranges, β indicated a fractal relationship (β6–60/h = 1.27 ± 0.01; β1–6/h = 1.80 ± 0.16). Conversely, the slope of the lowest frequency region (i.e., the shoulder) was nearly flat (β0.083–1 /h = 0.32 ± 0.28). We simulated the BP time series as a random walk about 100 mmHg with ranges above and below of 10, 30, and 50 mmHg and with Δ from 0.5 to 2.5. The spectrum for the conditions mimicking actual BP time series (i.e., range, 85–115 mmHg; Δ, 2.00) resembled the observed spectra, with β in the lowest frequency range = 0.207 and fractal-like behavior in the two higher frequency ranges (β = 1.707 and 2.057). We suggest that the combined actions of mechanisms limiting the excursion of arterial BP produce the shoulder in the spectrum and that Δ contributes to determining β.

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