Speed of phototransduction in the microvillus regulates the accuracy and bandwidth of the rhabdomeric photoreceptor

Phototransduction reactions in the rhabdomeric photoreceptor are profoundly stochastic due to the small number of participating molecules and small reaction space. The resulting quantum bumps (QBs) vary in their timing (latency), amplitudes and durations, and these variabilities within each cell are not correlated. Using modeling and electrophysiological recordings, we investigated how the QB properties depend on the cascade speed and how they influence signal transfer. Parametric analysis in the model supported by experimental data revealed that faster cascades elicit larger and narrower QBs with faster onsets and smaller variabilities than slower cascades. Latency dispersion was stronger affected by modification of upstream than downstream activation parameters. The variability caused by downstream modifications closely matched the experimental variability. Frequency response modeling showed that corner frequency is a reciprocal function of the characteristic duration of the multiphoton response, which, in turn, is a non-linear function of QB duration and latency dispersion. All QB variabilities contributed noise but only latency dispersion slowed and spread multiphoton responses, lowering the corner frequency. Using the discovered QB correlations, we evaluated transduction noise for dissimilar species and two extreme adaptation states, and compared it to photon noise. The noise emitted by the cascade was non-additive and depended non-linearly on the interaction between the QB duration and the three QB variabilities. Increased QB duration strongly suppressed both noise and corner frequency. This trade-off might be acceptable for nocturnal but not diurnal species because corner frequency is the principal determinant of information capacity. To offset the increase in noise accompanying the QB narrowing during light adaptation and the response-expanding effect of latency dispersion, the cascade accelerates. This explains the widespread evolutionary tendency of diurnal fliers to have fast phototransduction, especially after light adaptation, which thus appears to be a common adaptation to contain stochasticity, improve SNR and expand the bandwidth.

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Synchronizing vigilance or taking turns as sentinels? The importance of testing coordination

10.1101/2020.04.24.055707 ◽

2020 ◽

Author(s):

Annemarie van der Marel ◽

Jane M. Waterman ◽

Marta López-Darias

Keyword(s):

Habitat Structure ◽

High Quality ◽

Alarm Signal ◽

Trade Off ◽

Optimal Activity ◽

Behavioral Observations ◽

Individual Survival ◽

Low Costs ◽

The Cost ◽

Diurnal Species

AbstractDiurnal species can reduce the cost of the trade-off between feeding and predation risk by 1) performing low-quality (vigilance while performing another behavior) instead of high-quality vigilance (only performing vigilance) or 2) by vigilance coordination either by taking turns acting as sentinels or by synchronizing vigilance bouts. A sentinel system assumes that sentinels are located at raised positions, alarm signal, and alternate vigilance bouts. However, many species with a described sentinel system have not been tested yet for coordination. We set out to study coordinated behavior and the reasons for this behavior in the invasive Barbary ground squirrel, Atlantoxerus getulus, using behavioral observations and genetic analyses. This species performs a type of vigilance (‘perch behavior’) seemingly similar to sentinel behavior as individuals performed high-quality vigilance at raised locations for over 30 s, but alternating coordination is unknown. Perch behavior was coordinated but synchronized instead of taking turns (sentinel). Both sexes performed perch behavior and individuals performed perch behavior in the absence and presence of kin and offspring. We found that survival or time spent foraging did not decrease for perched individuals, nor that individual survival increased. Perch behavior in the invasive population of A. getulus may be synchronized 1) to perform an optimal activity when satiated (low costs), and, 2) may be an adaptation to habitat structure (large benefits). Our study demonstrates that the cost of the vigilance/foraging trade-off may not be high for invasive species and argued the importance of testing for coordination in species with described sentinel systems.

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Parametric Analysis of the Sensitivity of a Prestressed Concrete Beam Using the DOE Simulation Technique

Archives of Civil Engineering ◽

10.2478/ace-2019-0049 ◽

2019 ◽

Vol 65 (4) ◽

pp. 97-112

Author(s):

Sz. Woliński ◽

T. Pytlowany

Keyword(s):

Prestressed Concrete ◽

Parametric Analysis ◽

Concrete Beam ◽

Simulation Technique ◽

State Variables ◽

Trade Off ◽

Sensitivity Assessment ◽

Eurocode 2 ◽

Random State ◽

Selection Of

AbstractThe paper presents the method of simplified parametric analysis of the sensitivity of a pre-tensioned concrete beam. The presented approach is based on the DOE (design of experiments) data collection which is simulation technique allowing for identification of variables deciding about the effectiveness and costs of designed structures. Additionally, application of the hyper-surface of the construction response allows designers to the development of multi-dimensional trade-off graphs to facilitate, the assessment of the scope of changes in random state variables permitted due to the adequate criteria and selection of their values close to optimum. Design basics, procedures and results of the presented considerations of sensitivity assessment and reliability of the structure has been shown on the example of a pre-stressed concrete beam designed in accordance with the requirements and procedures of Eurocode 2

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Flexural Critical Speeds of a Two-Rotor Bearing System With One Overhang

13th Biennial Conference on Mechanical Vibration and Noise: Rotating Machinery and Vehicle Dynamics ◽

10.1115/detc1991-0226 ◽

1991 ◽

Author(s):

C. Y. Chow ◽

I-Chih Wang ◽

Rae Chow

Keyword(s):

Software Package ◽

Parametric Analysis ◽

Turbine Unit ◽

Wide Spectrum ◽

Industrial Applications ◽

Power Train ◽

Trade Off ◽

Critical Speeds ◽

Commercial Software Package ◽

Bearing System

Abstract Power-train arrangements, such as a two-rotor system with one overhang, have a wide spectrum of industrial applications, from a workbench grinder to compressor-turbine unit. Based on a typical dimension, flexural critical speeds both in the forward and backward whirl are calculated by a commercial software package. These critical speeds are further analyzed by varying the shaft overhung, rotor inertia and gyroscopic effect. Parametric analysis would enable designers to make a trade-off study and obtain a satisfactory operation. In extreme conditions, results obtained have been verified with available analytical solutions.

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The role of sensory adaptation in the retina

Journal of Experimental Biology ◽

10.1242/jeb.146.1.39 ◽

1989 ◽

Vol 146 (1) ◽

pp. 39-62 ◽

Cited By ~ 5

Author(s):

S. B. Laughlin

Keyword(s):

Information Transfer ◽

Light Adaptation ◽

Dynamic Range ◽

Range Limit ◽

Biological Organization ◽

Trade Off ◽

Amount Of Information ◽

Adaptation Mechanisms ◽

Trade Offs ◽

Common Trade

Adaptation, a change in response to a sustained stimulus, is a widespread property of sensory systems, occurring at many stages, from the most peripheral energy-gathering structures to neural networks. Adaptation is also implemented at many levels of biological organization, from the molecule to the organ. Despite adaptation's diversity, it is fruitful to extract some unifying principles by considering well-characterized components of the insect visual system. A major function of adaptation is to increase the amount of sensory information an organism uses. The amount of information available to an organism is ultimately defined by its environment and its size. The amount of information collected depends upon the ways in which an organism samples and transduces signals. The amount of information that is used is further limited by internal losses during transmission and processing. Adaptation can increase information capture and reduce internal losses by minimizing the effects of physical and biophysical constraints. Optical adaptation mechanisms in compound eyes illustrate a common trade-off between energy (quantum catch) and acuity (sensitivity to changes in the distribution of energy). This trade-off can be carefully regulated to maximize the information gathered (i.e. the number of pictures an eye can reconstruct). Similar trade-offs can be performed neurally by area summation mechanisms. Light adaptation in photoreceptors introduces the roles played by cellular constraints in limiting the available information. Adaptation mechanisms prevent saturation and, by trading gain for temporal acuity, increase the rate of information uptake. By minimizing the constraint of nonlinear summation (imposed by membrane conductance mechanisms) a cell's sensitivity follows the Weber-Fechner law. Thus, a computationally advantageous transformation is generated in response to a cellular constraint. The synaptic transfer of signals from photoreceptors to second-order neurones emphasizes that the cellular constraints of nonlinearity, noise and dynamic range limit the transmission of information from cell to cell. Synaptic amplification is increased to reduce the effects of noise but this resurrects the constraint of dynamic range. Adaptation mechanisms, both confined to single synapses and distributed in networks, remove spatially and temporally redundant signal components to help accommodate more information within a single cell. The net effect is a computationally advantageous removal of the background signal. Again, the cellular constraints on information transfer have dictated a computationally advantageous operation.

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Review for "Light adaptation mechanisms in the eye of the fiddler crab Afruca tangeri"

10.1002/cne.24973/v1/review2 ◽

2020 ◽

Keyword(s):

Light Adaptation ◽

Fiddler Crab ◽

Adaptation Mechanisms

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Decision letter for "Light adaptation mechanisms in the eye of the fiddler crab Afruca tangeri"

10.1002/cne.24973/v2/decision1 ◽

2020 ◽

Keyword(s):

Light Adaptation ◽

Fiddler Crab ◽

Adaptation Mechanisms

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The Effect of Kalman-Weighted Averaging and Artifact Rejection on Residual Noise During Auditory Brainstem Response Testing

American Journal of Audiology ◽

10.1044/2018_aja-18-0123 ◽

2019 ◽

Vol 28 (1) ◽

pp. 114-124

Author(s):

Linda W. Norrix ◽

Julie Thein ◽

David Velenovsky

Keyword(s):

Repeated Measures ◽

Auditory Brainstem ◽

Weighted Averaging ◽

Auditory Brainstem Responses ◽

Residual Noise ◽

Electrophysiological Recordings ◽

Artifact Rejection ◽

Brainstem Response ◽

Active Motor ◽

Averaging Time

Purpose Low residual noise (RN) levels are critically important when obtaining electrophysiological recordings of threshold auditory brainstem responses. In this study, we examine the effectiveness and efficiency of Kalman-weighted averaging (KWA) implemented on the Vivosonic Integrity System and artifact rejection (AR) implemented on the Intelligent Hearing Systems SmartEP system for obtaining low RN levels. Method Sixteen adults participated. Electrophysiological measures were obtained using simultaneous recordings by the Vivosonic and Intelligent Hearing Systems for subjects in 2 relaxed conditions and 4 active motor conditions. Three averaging times were used for the relaxed states (1, 1.5, and 3 min) and for the active states (1.5, 3, and 6 min). Repeated-measures analyses of variance were used to examine RN levels as a function of noise reduction strategy (i.e., KWA, AR) and averaging time. Results Lower RN levels were obtained using KWA than AR in both the relaxed and active motor states. Thus, KWA was more effective than was AR under the conditions examined in this study. Using KWA, approximately 3 min of averaging was needed in the relaxed condition to obtain an average RN level of 0.025 μV. In contrast, in the active motor conditions, approximately 6 min of averaging was required using KWA. Mean RN levels of 0.025 μV were not attained using AR. Conclusions When patients are not physiologically quiet, low RN levels are more likely to be obtained and more efficiently obtained using KWA than AR. However, even when using KWA, in active motor states, 6 min of averaging or more may be required to obtain threshold responses. Averaging time needed and whether a low RN level can be attained will depend on the level of motor activity exhibited by the patient.

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