scholarly journals Effects of phase correlations in naturalistic stimuli on quantitative information coding by fly photoreceptors

2018 ◽  
Vol 119 (6) ◽  
pp. 2276-2290 ◽  
Author(s):  
Irina I. Ignatova ◽  
Andrew S. French ◽  
Roman V. Frolov
Keyword(s):  
Information Content ◽  
Information Transfer ◽  
Early Stage ◽  
Higher Order ◽  
Calliphora Vicina ◽  
Local Contrast ◽  
Time And Space ◽  
Random Signals ◽  
Visual Scenes ◽  
Phase Randomization

Natural visual scenes are rarely random. Instead, intensity and wavelength change slowly in time and space over many regions of the scene, so that neighboring temporal and spatial visual inputs are more correlated and contain less information than truly random signals. It has been suggested that sensory optimization to match these higher order correlations (HOC) occurs at the earliest visual stages, and that photoreceptors can process temporal natural signals more efficiently than random signals. We tested this early-stage hypothesis by comparing the information content of Calliphora vicina photoreceptor responses to naturalistic inputs before and after removing HOC by randomizing phase. Forty different, 60-s long, naturalistic sequences (NS) were used, together with randomized-phase versions of the same sequences to give pink noise (PN) so that each input pair had identical means, variances, mean contrasts, and power spectra. We measured the information content of inputs and membrane potential responses by three different methods: coherence, mutual information, and compression entropy. We also used entropy and phase statistics of each pair as measures of HOC. Responses to randomized signals generally had higher gain, signal-to-noise ratio, and information rates than responses to NS. Information rate increased with a strong, positive, linear correlation to phase randomization within sequence pairs. This was confirmed by varying the degree of phase randomization. Our data indicate that individual photoreceptors encode input information by Weber’s law, with HOC within natural sequences reducing information transfer by decreasing the number of local contrast events that exceed the noise-imposed threshold. NEW & NOTEWORTHY Natural visual scenes feature statistical regularities, or higher order correlations (HOC), both in time and space, to encode surfaces, textures, and object boundaries. Visual systems rely on this information; however, it remains controversial whether individual photoreceptors can discriminate and enhance information encoded in HOC. Here we show that the more HOC the stimulus contains, the lower the information transfer rate of photoreceptors. We explain our findings by applying the Weber’s paradigm of differential signal perception.

Analytical and experimental study on Van der Pol-type and Rayleigh-type equations for modeling nonlinear aeroelastic instabilities

2021 ◽  
pp. 136943322110220
Author(s):  
Guangzhong Gao ◽  
Ledong Zhu ◽  
Hua Bai ◽  
Wanshui Han ◽  
Feng Wang
Keyword(s):  
Aerodynamic Force ◽  
Early Stage ◽  
Higher Order ◽  
Empirical Modeling ◽  
Identification Algorithm ◽  
Van Der Pol ◽  
Single Degree Of Freedom ◽  
Section Shape ◽  
Vibration Responses ◽  
Aerodynamic Parameters

An empirical modeling of nonlinear aerodynamic force during aeroelastic instabilities, that is, vortex-induced vibration (VIV), galloping and flutter, is necessary in the estimation of vibration responses. Previous works on single-degree-of-freedom (SDOF) models suggest that nonlinear forms (Van der Pol or Rayleigh types) differ from section to section, which causes difficulty in practical application. Analytical evidences in this study have clarified that Van der Pol-type and Rayleigh-type models are equivalent in the amplitude-dependent aerodynamic damping; their difference lies in the higher-order harmonic responses. An identification algorithm of aerodynamic parameters is proposed to improve the robustness of aerodynamic parameters and guarantee the equivalence of both model types. Wind-tunnel tests of typical aeroelastic instabilities indicate that higher-order harmonic responses are small for VIV, galloping, and early-stage flutter instability when compared with the fundamental components due to weak nonlinearity. Van der Pol-type and Rayleigh-type models are both applicable until the flutter amplitude grows excessively large. It is clear that both model types are suitable for any section shape when use the proposed method of aerodynamic identification, and thus can be treated as a universal model for estimating the vibration amplitudes of nonlinear aeroelastic instabilities.

scholarly journals Information content of visual scenes influences systematic search of desert ants

2012 ◽  
Vol 216 (4) ◽  
pp. 742-749 ◽  
Author(s):  
P. Schultheiss ◽  
A. Wystrach ◽  
E. L. G. Legge ◽  
K. Cheng
Keyword(s):  
Information Content ◽  
Systematic Search ◽  
Desert Ants ◽  
Visual Scenes

scholarly journals Design of Instrument Approach Procedure Charts: Comprehending Missed Approach Instructions Coded in Text or Icons

1992 ◽  
Vol 36 (18) ◽  
pp. 1455-1459
Author(s):  
David W. Osborne ◽  
M. Stephen Huntley
Keyword(s):  
Information Content ◽  
Information Transfer ◽  
Transfer Efficiency ◽  
High Information Content ◽  
Efficient Information ◽  
Report Accuracy ◽  
Text Version ◽  
High Information

The objectives of this experiment were to determine whether coding missed approach instructions in text or icons would result in more efficient information transfer, and if the information transfer efficiency for either coding technique was dependent upon the level of information content. Twelve pilots currently licensed for instrument (IFR) flight participated as subjects. Text instructions were either taken directly or developed from instructions found on National Ocean Service (NOS) instrument approach procedure charts. These instructions possessed one of three levels of information content: low, medium, and high. Across the range of information content levels, iconic missed approach instructions were comprehended more quickly and as accurately as instructions coded in text of the font style and size used by NOS. Regardless of coding technique, report accuracy was significantly worse for instructions with a high information content level. Pilots indicated that in single pilot IFR conditions, they would rather have the iconic than the text version of the missed approach instructions.

Texture Segregation in the Human Visual Cortex: A Functional MRI Study

2000 ◽  
Vol 83 (4) ◽  
pp. 2453-2457 ◽  
Author(s):  
Sabine Kastner ◽  
Peter De Weerd ◽  
Leslie G. Ungerleider
Keyword(s):  
Visual Cortex ◽  
Functional Mri ◽  
Receptive Fields ◽  
Higher Order ◽  
Checkerboard Pattern ◽  
Texture Segregation ◽  
Human Visual Cortex ◽  
Cell Recording ◽  
Visual Scenes ◽  
Mri Study

The segregation of visual scenes based on contour information is a fundamental process of early vision. Contours can be defined by simple cues, such as luminance, as well as by more complex cues, such as texture. Single-cell recording studies in monkeys suggest that the neural processing of complex contours starts as early as primary visual cortex. Additionally, lesion studies in monkeys indicate an important contribution of higher order areas to these processes. Using functional MRI, we have investigated the level at which neural correlates of texture segregation can be found in the human visual cortex. Activity evoked by line textures, with and without texture-defined boundaries, was compared in five healthy subjects. Areas V1, V2/VP, V4, TEO, and V3A were activated by both kinds of line textures as compared with blank presentations. Textures with boundaries forming a checkerboard pattern, relative to uniform textures, evoked significantly more activity in areas V4, TEO, less reliably in V3A, but not in V1 or V2/VP. These results provide evidence that higher order areas with large receptive fields play an important role in the segregation of visual scenes based on texture-defined boundaries.

scholarly journals The "principles" paper: some thoughts on an unusual hybrid

2012 ◽  
Vol 36 (113) ◽  
pp. 99-113
Author(s):  
Andrew Kenneth Shenton
Keyword(s):  
Higher Order ◽  
Abstract Thinking ◽  
Time And Space ◽  
Significant Step ◽  
The Creation ◽  
Research Students

For years, ‘principles’ papers have made an important contribution to LIS literature and their influence on subsequent writers has been considerable. They make a series of concise claims in relation to a topic, which are usually supported by a variety of evidence and are pertinent across time and space. These claims have emerged from the literature or are derived directly from the author’s own experience. In writing such a piece, research students may seek to enhance their abstract thinking abilities, whilst practitioners benefit from considering their work more critically and from contextualising their day-to-day experience in terms of wider knowledge. Although ‘principles’ papers are difficult to construct, a would-be writer should not be deterred, as readers are likely to appreciate the ease with which the main claims can be seen, and the paper may form a significant step towards the creation of higher order work.

scholarly journals Online Signature Analysis for Characterizing Early Stage Alzheimer’s Disease: A Feasibility Study

Entropy ◽  
2019 ◽  
Vol 21 (10) ◽  
pp. 956
Author(s):  
Zelong Wang ◽  
Majd Abazid ◽  
Nesma Houmani ◽  
Sonia Garcia-Salicetti ◽  
Anne-Sophie Rigaud
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Information Content ◽  
Early Stage ◽  
A Priori ◽  
Support Vector ◽  
Linear Discriminant ◽  
Linear Classifiers ◽  
Online Signature ◽  
Time Sequences

We aimed to explore the online signature modality for characterizing early-stage Alzheimer’s disease (AD). A few studies have explored this modality, whereas many on online handwriting have been published. We focused on the analysis of raw temporal functions acquired by the digitizer on signatures produced during a simulated check-filling task. Sample entropy was exploited to measure the information content in raw time sequences. We show that signatures of early-stage AD patients have lower information content than those of healthy persons, especially in the time sequences of pen pressure and pen altitude angle with respect to the tablet. The combination of entropy values on two signatures for each person was classified with two linear classifiers often used in the literature: support vector machine and linear discriminant analysis. The improvements in sensitivity and specificity were significant with respect to the a priori group probabilities in our population of AD patients and healthy subjects. We show that altitude angle, when combined with pen pressure, conveys crucial information on the wrist-hand-finger system during signature production for pathology detection.

Information content of visual scenes influences systematic search of desert ants (Melophorus bagoti)

2012 ◽  
Author(s):  
Eric L. G. Legge ◽  
Patrick Schultheiss ◽  
Antoine Wystrach ◽  
Marcia L. Spetch ◽  
Ken Cheng
Keyword(s):  
Information Content ◽  
Systematic Search ◽  
Desert Ants ◽  
Visual Scenes ◽  
Melophorus Bagoti

scholarly journals Dynamical Phase Modulation and Oscillatory Detuning in Applied Neurostimulation

2020 ◽  
Vol 7 (1) ◽  
pp. 01-10
Author(s):  
Denis Larrivee
Keyword(s):  
Information Exchange ◽  
Phase Modulation ◽  
Information Transfer ◽  
Phase Locking ◽  
Motor Planning ◽  
Higher Order ◽  
Brain Organization ◽  
Dynamical Phase ◽  
Dynamical Features ◽  
Global Brain

Neural architectures that are operative in higher order cognition, including consciousness, memory, and motor planning, undergo complex changes in global organization during neurological disease. Increasingly, neurostimulation is therapeutically used for restoring these functions, although the mechanisms of restoration are largely unknown. Extant studies reveal, on the other hand, that non-linear and dynamical principles govern global brain organization, seen in operational features such as persistence, stability, flexibility and non-localization that are likely to be evoked by neurostimulation. These dynamical features are instantiated in neural oscillations, a key mechanism regulating brain function and communication. Due to stochastic influences, oscillator synchronization and desynchronization exhibit limit cycle attractor dynamics, which are characterized by persistent phase modulation rather than fixed point, stationary phase locking. Phase modulation governs information exchange by temporally gating transfer and guiding the trajectory of information distribution. Activation of attractor forces by modest input drive induces dynamic, phase difference detuning that results in phase preference shifts, whereas strong input drive induces low stability phase relations that promote oscillator dissociation and new pair formation. These dynamical features of oscillator behavior are likely to facilitate information transfer to neural networks during neurostimulation of higher order functions.

The Special Form of Second Order Accuracy N-S Equations for Incompressible Fluid

2014 ◽  
Vol 644-650 ◽  
pp. 1644-1647
Author(s):  
Zhan Song Li ◽  
Shi Jiang Zhu
Keyword(s):  
Laminar Flow ◽  
Turbulent Flow ◽  
Incompressible Fluid ◽  
Special Form ◽  
Higher Order ◽  
Second Order ◽  
Time And Space ◽  
Order Accuracy ◽  
First Order

Classic N-S equation has first order accuracy in both of time and space. It has only the terms of first order, without the terms of second or higher order. These terms are relative in time and space steps. The time and space steps, as basic elements of fluid research, should be only some finite quantities and not be infinitely near to zero as defined in mathematics. If the terms of second or higher order can be ignored depends on the value of the corresponding derivative multiplied. Compared with terms of first order, the terms of second or higher order can be ignored under the condition of laminar flow. However, under the condition of turbulent flow, these can’t be ignored yet. When turbulent flow develops fully, the terms of first order, compared with terms of second order, can be ignored. So, it is why classic N-S equations aren’t closed when they are used to analyze turbulent flow. On the basic, many different special forms of the second order accuracy N-S equations of incompressible fluid are derived.

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