Two Interacting Olfactory Transduction Mechanisms Have Linked Polarities and Dynamics in Drosophila melanogaster Antennal Basiconic Sensilla Neurons

2009 ◽  
Vol 102 (1) ◽  
pp. 214-223 ◽  
Author(s):  
Julia Schuckel ◽  
Päivi H. Torkkeli ◽  
Andrew S. French
Keyword(s):  
Drosophila Melanogaster ◽  
Signal To Noise Ratio ◽  
Coherence Function ◽  
Information Capacity ◽  
Linear Filter ◽  
Large Signal ◽  
Limited Bandwidth ◽  
Basiconic Sensilla ◽  
Frequency Responses ◽  
Band Pass

We measured frequency response functions between concentrations of fruit odorants and individual action potentials in large basiconic sensilla of the Drosophila melanogaster antenna. A new method of randomly varying odorant concentration was combined with rapid, continuous measurement of concentration at the antenna by a miniature photoionization detector. All frequency responses decreased progressively at frequencies approaching 100 Hz, providing an upper limit for the dynamics of Drosophila olfaction. We found two distinct response patterns: excitatory band-pass frequency responses were seen with ethyl acetate, ethyl butyrate, and hexanol, whereas inhibitory low-pass responses were seen with methyl salicylate and phenylethyl acetate. Band-pass responses peaked at 1–10 Hz. Frequency responses could be well fitted by simple linear filter equations, and the fitted parameters were consistent within each of the two types of responses. Experiments with equal mixtures of excitatory and inhibitory odorants gave responses that were characteristic of the inhibitory components, indicating that interaction during transduction causes inhibitory odorants to suppress the responses to excitatory odorants. Plots of response amplitude versus odorant concentration indicated that the odorant concentrations used were within approximately linear regions of the dose response relationships. We also estimated linear information capacity from the coherence function of each recording. Although coherence was relatively high, indicating a large signal-to-noise ratio, information capacity for olfaction was much lower than comparable estimates for mechanotransduction or visual transduction because of the limited bandwidth of olfaction. These data offer new insights into transduction by primary chemoreceptors and place temporal constraints on Drosophila olfactory behavior.

scholarly journals Contrast gain, signal-to-noise ratio, and linearity in light-adapted blowfly photoreceptors.

1994 ◽  
Vol 104 (3) ◽  
pp. 593-621 ◽  
Author(s):  
M Juusola ◽  
E Kouvalainen ◽  
M Järvilehto ◽  
M Weckström
Keyword(s):  
Light Adaptation ◽  
Dead Time ◽  
Signal To Noise Ratio ◽  
Coherence Function ◽  
Calliphora Vicina ◽  
Signal To Noise ◽  
Low Frequencies ◽  
Contrast Gain ◽  
Frequency Responses ◽  
Phase Functions

Response properties of short-type (R1-6) photoreceptors of the blowfly (Calliphora vicina) were investigated with intracellular recordings using repeated sequences of pseudorandomly modulated light contrast stimuli at adapting backgrounds covering 5 log intensity units. The resulting voltage responses were used to determine the effects of adaptational regulation on signal-to-noise ratios (SNR), signal induced noise, contrast gain, linearity and the dead time in phototransduction. In light adaptation the SNR of the photoreceptors improved more than 100-fold due to (a) increased photoreceptor voltage responses to a contrast stimulus and (b) reduction of voltage noise at high intensity backgrounds. In the frequency domain the SNR was attenuated in low frequencies with an increase in the middle and high frequency ranges. A pseudorandom contrast stimulus by itself did not produce any additional noise. The contrast gain of the photoreceptor frequency responses increased with mean illumination and the gain was best fitted with a model consisting of two second order and one double pole of first order. The coherence function (a normalized measure of linearity and SNR) of the frequency responses demonstrated that the photoreceptors responded linearly (from 1 to 150 Hz) to the contrast stimuli even under fairly dim conditions. The theoretically derived and the recorded phase functions were used to calculate phototransduction dead time, which decreased in light adaptation from approximately 5-2.5 ms. This analysis suggests that the ability of fly photoreceptors to maintain linear performance under dynamic stimulation conditions results from the high early gain followed by delayed compressive feed-back mechanisms.

IMPROVEMENTS IN THE CONTINUOUS SEISMIC PROFILER

Geophysics ◽  
1965 ◽  
Vol 30 (1) ◽  
pp. 133-138 ◽  
Author(s):  
David D. Caulfield ◽  
Hartley Hoskins ◽  
Richard T. Nowak
Keyword(s):  
Matched Filter ◽  
Signal To Noise Ratio ◽  
Electrical Energy ◽  
Linear Filter ◽  
Woods Hole Oceanographic Institution ◽  
Sea Floor ◽  
Band Pass ◽  
Neutrally Buoyant ◽  
Peak Pressures ◽  
Hydrophone Array

The continuous seismic profiling system used at the Woods Hole Oceanographic Institution now has (1) an electrical spark sound source which has a maximum stored energy of 100,000 joules and can produce a variety of acoustic pulses with peak pressures of up to 134 db above [Formula: see text], at a repetition period of 10 sec, and which has a conversion efficiency (stored electrical energy to sound energy radiated) of 10 percent, (2) a streamlined and uniformly neutrally buoyant line‐hydrophone array with a band‐pass of 20 to 1,000 cps, and (3) a matched‐filter detector that measures the correlation between the reflected signal and the waveform incident on the sea floor in the same frequency range as the reflection. A source whose sonic output can be varied readily makes possible tailoring the resolution of the system for the best display of features of the oceanic crust of varying vertical size. A large reduction in the self‐noise of the detector is achieved through the use of streamlined, stable‐towing, line‐hydrophone arrays which also discriminate against the noises of the towing vessel. A matched‐filter detector gives the maximum signal‐to‐noise ratio obtainable from a linear filter, and an eight‐fold improvement over the rectified amplitude presentation formerly used has been obtained. Reflections from 0.8 sec beneath the sea floor in continental shelf areas have been obtained at ship speeds of eleven knots and from 1.8 sec beneath the sea floor in the deep sea at six knots.

Information capacity and bandwidth limitations in the SEM

1989 ◽  
Vol 47 ◽  
pp. 84-85
Author(s):  
D. C. Joy ◽  
R. D. Bunn
Keyword(s):  
Signal To Noise Ratio ◽  
Critical Dimension ◽  
Information Capacity ◽  
Acquisition Time ◽  
Signal To Noise ◽  
Sem Image ◽  
Probe Size ◽  
Minimum Number ◽  
Noise Ratio ◽  
Signal Channel

The information available from an SEM image is limited both by the inherent signal to noise ratio that characterizes the image and as a result of the transformations that it may undergo as it is passed through the amplifying circuits of the instrument. In applications such as Critical Dimension Metrology it is necessary to be able to quantify these limitations in order to be able to assess the likely precision of any measurement made with the microscope.The information capacity of an SEM signal, defined as the minimum number of bits needed to encode the output signal, depends on the signal to noise ratio of the image - which in turn depends on the probe size and source brightness and acquisition time per pixel - and on the efficiency of the specimen in producing the signal that is being observed. A detailed analysis of the secondary electron case shows that the information capacity C (bits/pixel) of the SEM signal channel could be written as :

Gravity meter observation of free modes excited by the August 19, 1977 Indonesia earthquake

1979 ◽  
Vol 69 (5) ◽  
pp. 1445-1454
Author(s):  
John A. Linton ◽  
D. E. Smylie ◽  
O. G. Jensen
Keyword(s):  
Signal To Noise Ratio ◽  
Quartz Fiber ◽  
Large Signal ◽  
Signal To Noise ◽  
Definitive Evidence ◽  
Long Period ◽  
Noise Ratio

abstract Free modes with signal-to-noise ratio in the range of 40 to 55 dB were observed in the record taken by a vertical broadband quartz fiber gravimeter system opeating in Montreal following the event of August 19, 1977 in Indonesia. The large signal-to-noise ratio has permitted very stable Q estimates to be made for a number of the fundamental spheroidal modes. The very long-period band shows no definitive evidence of signal other than the expected tidal lines.

scholarly journals Artifacts removal from breath sound recordings in pediatric population

2018 ◽  
Vol 154 ◽  
pp. 01046
Author(s):  
Yusuf A Amrulloh ◽  
Jawahir A K Haq
Keyword(s):  
Signal To Noise Ratio ◽  
Pediatric Population ◽  
Breath Sound ◽  
Discrete Wavelet ◽  
Band Pass Filter ◽  
Pass Filter ◽  
Sound Recordings ◽  
Breath Sounds ◽  
Band Pass ◽  
Lower Magnitude

Breath sound recordings from pediatric subjects pose more processing complications. Children, especially the younger ones, are not able to follow instructions to stay calm during recording. This makes their recordings not only contain stationary artifacts but also non-stationary artifacts such as movement of subjects and their heartbeats. Further, the breath sounds from pediatric subjects also have lower magnitude compared to adults. In this work, we proposed to address those problems by developing a method to remove the artifacts from breath sound recordings. We implemented a combination of a Butterworth band pass filter and a discrete wavelet filter. We tested three types of wavelets (Coiflet, Symlet and Daubechies). Ten level decompositions and a set of hard thresholds were implemented in our work. Our results show that our developed method was capable of removing the artifacts significantly while maintaining the signal of interest. The highest signal to noise ratio improvement (10.65dB) was achieved by 32 orders Symlet.

scholarly journals Propagating Wave and Irregular Dynamics: Spatiotemporal Patterns of Cholinergic Theta Oscillations in Neocortex In Vitro

2003 ◽  
Vol 90 (1) ◽  
pp. 333-341 ◽  
Author(s):  
Weili Bao ◽  
Jian-Young Wu
Keyword(s):  
Phase Distribution ◽  
Signal To Noise Ratio ◽  
Human Subjects ◽  
Local Oscillator ◽  
Spatiotemporal Patterns ◽  
Spatiotemporal Pattern ◽  
Large Signal ◽  
Local Oscillators ◽  
Theta Oscillation

Neocortical “theta” oscillation (5–12 Hz) has been observed in animals and human subjects but little is known about how the oscillation is organized in the cortical intrinsic networks. Here we use voltage-sensitive dye and optical imaging to study a carbachol/bicuculline induced theta (∼8 Hz) oscillation in rat neocortical slices. The imaging has large signal-to-noise ratio, allowing us to map the phase distribution over the neocortical tissue during the oscillation. The oscillation was organized as spontaneous epochs and each epoch was composed of a “first spike,” a “regular” period (with relatively stable frequency and amplitude), and an “irregular” period (with variable frequency and amplitude) of oscillations. During each cycle of the regular oscillation, one wave of activation propagated horizontally (parallel to the cortical lamina) across the cortical section at a velocity of ∼50 mm/s. Vertically the activity was synchronized through all cortical layers. This pattern of one propagating wave associated with one oscillation cycle was seen during all the regular cycles. The oscillation frequency varied noticeably at two neighboring horizontal locations (330 μm apart), suggesting that the oscillation is locally organized and each local oscillator is about ≤300 μm wide horizontally. During irregular oscillations, the spatiotemporal patterns were complex and sometimes the vertical synchronization decomposed, suggesting a de-coupling among local oscillators. Our data suggested that neocortical theta oscillation is sustained by multiple local oscillators. The coupling regime among the oscillators may determine the spatiotemporal pattern and switching between propagating waves and irregular patterns.

scholarly journals DESIGN OF BAND-PASS FILTERS WITH NON-EQUIRIPPLE FREQUENCY RESPONSES

2019 ◽  
Vol 22 (3) ◽  
pp. 5-23
Author(s):  
Evgeniy N. Chervinskiy
Keyword(s):  
Frequency Response ◽  
Special Functions ◽  
Band Pass Filter ◽  
System Of Equations ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Frequency Responses ◽  
Band Pass ◽  
Standard Values ◽  
Circuit Elements

Introduction. Band-pass filters circuit elements can be calculated by converting low-pass filter (LPF) parameters, which is the prototype of the designed band-pass filter. The conversion causes problems in case calculated values of circuit elements (resistors and capacitors) are out of standard values determined by the GOST standard. Obviously, frequency characteristics of band-pass filters are distorted when replacing the calculated values of circuit elements by the standard ones. The number of circuit elements with values different from standard can be reduced to zero by solving an additional system of equations that connects parameters of designed and reintroduced non-equiripple frequency responses. Objective. The objective of this work is to develop a calculation method of band-pass ladder filters with values of circuit elements corresponding to standard ones. Materials and methods. The filter design process includes two stages. The first stage is a parameters calculation of a polynomial LPF prototype. The calculated parameters are determined as a system of equations solution set. The equations are formed by equating coefficients of variables raised to the same powers in transfer function (TF) expressions of designed and realized filters. Initial characteristics are the filter order and frequency response unevenness. The transition to the standard values of circuit elements can be done when solving another system of equations that connects LPF converted parameters with unknown parameters of reintroduced non-equiripple frequency response. Results. TF of LPF prototypes up to the fifth order and frequency responses of band-pass filters (BPF) and bandrejection filters up to the tenth order are presented. Analytical expressions of non-equiripple and equiripple frequency responses are used to estimate distortions of the latter when a band-pass filter center frequency is tuned by using variable inductors or capacitors. The integral quadratic function of a variable is taken as a measure of real frequency response distortions. The tenth order BPF calculation example is given. Conclusion. The presented calculation methods of band-pass filters and given example demonstrate possibilities of the filter design method based on the systems of non-linear equations solution. In contrast to approximation methods of ideal filter frequency response by using special functions and tabular filters design, the presented method allows high-order filter calculation for any initial requirements without using reference data.

scholarly journals Assessing Neuronal Coherence with Single-Unit, Multi-Unit, and Local Field Potentials

2006 ◽  
Vol 18 (9) ◽  
pp. 2256-2281 ◽  
Author(s):  
Magteld Zeitler ◽  
Pascal Fries ◽  
Stan Gielen
Keyword(s):  
Unit Activity ◽  
Single Unit ◽  
Signal To Noise Ratio ◽  
Coherence Function ◽  
Accurate Estimate ◽  
Unit Recording ◽  
Output Spike ◽  
Monkey Visual Cortex ◽  
Neuronal Coherence ◽  
Unit Spike

The purpose of this study was to obtain a better understanding of neuronal responses to correlated input, in particular focusing on the aspect of synchronization of neuronal activity. The first aim was to obtain an analytical expression for the coherence between the output spike train and correlated input and for the coherence between output spike trains of neurons with correlated input. For Poisson neurons, we could derive that the peak of the coherence between the correlated input and multi-unit activity increases proportionally with the square root of the number of neurons in the multi-unit recording. The coherence between two typical multi-unit recordings (2 to 10 single units) with partially correlated input increases proportionally with the number of units in the multi-unit recordings. The second aim of this study was to investigate to what extent the amplitude and signal-to-noise ratio of the coherence between input and output varied for single-unit versus multi-unit activity and how they are affected by the duration of the recording. The same problem was addressed for the coherence between two single-unit spike series and between two multi-unit spike series. The analytical results for the Poisson neuron and numerical simulations for the conductance-based leaky integrate-and-fire neuron and for the conductance-based Hodgkin-Huxley neuron show that the expectation value of the coherence function does not increase for a longer duration of the recording. The only effect of a longer duration of the spike recording is a reduction of the noise in the coherence function. The results of analytical derivations and computer simulations for model neurons show that the coherence for multi-unit activity is larger than that for single-unit activity. This is in agreement with the results of experimental data obtained from monkey visual cortex (V4). Finally, we show that multitaper techniques greatly contribute to a more accurate estimate of the coherence by reducing the bias and variance in the coherence estimate.

Metastable yield of argon between 23 and 37 eV by electron impact

1979 ◽  
Vol 57 (10) ◽  
pp. 1624-1633 ◽  
Author(s):  
P. Marchand ◽  
J. Cardinal
Keyword(s):  
Electron Impact ◽  
Excited States ◽  
Signal To Noise Ratio ◽  
Negative Ion ◽  
Photon Yield ◽  
Large Signal ◽  
Signal To Noise ◽  
Monoenergetic Electron ◽  
Yield Curves ◽  
Noise Ratio

The metastable yield of argon excited by monoenergetic electron impact has been measured between 23 and 37 eV. Thanks to a large signal-to-noise ratio, many very small structures have been detected superimposed on the metastable continuum and are attributed to Ar− negative-ion states and to highly excited states of Ar. The results are compared with broadband photon yield curves and electroionization curves.

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