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Adaptation reduces variability of the neuronal population code

Physical Review E 2011年第5期83卷 050905(R)-050905(R)页

作者： Farzad Farkhooi Eilif Muller Martin P. Nawrot Neuroinformatics and Theoretical Neuroscience Freie Universität Berlin and BCCN-Berlin Germany Brain Mind Institute EPFL Lausanne Switzerland

Sequences of events in noise-driven excitable systems with slow variables often show serial correlations among their intervals of events. Here, we employ a master equation for generalized non-renewal processes to calculate the interval and count statistics of superimposed processes governed by a slow adaptation variable. For an ensemble of neurons with spike-frequency adaptation, this results in the regularization of the population activity and an enhanced postsynaptic signal decoding. We confirm our theoretical results in a population of cortical neurons recorded in vivo.

关键词： CORRELATION (Statistics) decoding algorithms VARIABLES (Mathematics) STATISTICS DIFFERENCES EQUATIONS

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Sign-Magnitude Decomposition of Mutual Information with Polarization Effect in Digital Identification

Sign-Magnitude Decomposition of Mutual Information with Pola...

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IEEE Information Theory Workshop (ITW)

作者： Voloshynovskiy, Svyatoslav Holotyak, Taras Koval, Oleksiy Beekhof, Fokko Farhadzadeh, Farzad Univ Geneva Dept Comp Sci CH-1211 Geneva 4 Switzerland

ISBN: (纸本)9781457704376

Content identification based on digital fingerprinting attracts a lot of attention in different emerging applications. In this paper, we consider digital identification based on the sign-magnitude decomposition of fingerprint codewords and analyze the achievable rates for each component. We introduce a channel splitting approach and reveal certain interesting phenomena related to channel polarization. It is demonstrated that under certain conditions almost all rate in the sign channel is concentrated in reliable components, this can be of interest for complexity and security in various content identification applications. The envisioned extensions cover applications where the input and output alphabets of the channel are different at the encoding and decoding stages. Additionally, the reduction of the input data dimensionality at the encoding/enrollment stage can increase the cryptographic protection in terms of privacy leakage and simplify the decoding algorithms in biometric applications.

关键词： Conferences decoding Entropy Mutual information Random variables Reliability Signal to noise ratio channel coding channel polarization channel splitting approach content identification cryptographic protection decoding decoding algorithms digital fingerpr

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Adaptive coded aperture imaging: progress and potential future applications

Adaptive coded aperture imaging: progress and potential futu...

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Conference on Unconventional Imaging, Wavefront Sensing, and Adaptive Coded Aperture Imaging and Non-Imaging Sensor Systems

作者： Gottesman, Stephen R. Isser, Abraham Gigioli, George W., Jr. Northrop Grumman Elect Syst Linthicum MD 21090 USA

ISBN: (纸本)9780819487759

Interest in Adaptive Coded Aperture Imaging (ACAI) continues to grow as the optical and systems engineering community becomes increasingly aware of ACAI's potential benefits in the design and performance of both imaging and non-imaging systems, such as good angular resolution (IFOV), wide distortion-free field of view (FOV), excellent image quality, and light weight construct. In this presentation we first review the accomplishments made over the past five years, then expand on previously published work to show how replacement of conventional imaging optics with coded apertures can lead to a reduction in system size and weight. We also present a trade space analysis of key design parameters of coded apertures and review potential applications as replacement for traditional imaging optics. Results will be presented, based on last year's work of our investigation into the trade space of IFOV, resolution, effective focal length, and wavelength of incident radiation for coded aperture architectures. Finally we discuss the potential application of coded apertures for replacing objective lenses of night vision goggles (NVGs).

关键词： Adaptive coded aperture imaging (ACAI) decoding algorithms night vision goggles (NVGs) angular resolution coded aperture imaging image reconstruction system point spread function (SPSF) MURAs

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Quantum Cyclic Code of Length Dividing p^t+1

Quantum Cyclic Code of Length Dividing pt+...

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IEEE International Symposium on Information Theory (ISIT)

作者： Dutta, Sagarmoy Kurur, Piyush P. Indian Inst Technol Dept Comp Sci & Engn Kanpur 208016 Uttar Pradesh India

ISBN: (纸本)9781457705953

In this paper, we study cyclic stabiliser codes over F-p of length dividing p(t) + 1 for some positive integer t. We call these t-Frobenius codes or just Frobenius codes for short. We give methods to construct them and show that they have efficient decoding algorithms. An important subclass of stabiliser codes are the linear stabiliser codes. For linear Frobenius codes we have stronger results: We completely characterise all linear Frobenius codes. As a consequence, we show that for every integer n that divides p(t) + 1 for an odd t, there are no linear cyclic codes of length n. On the other hand for even t, we give an explicit method to construct all of them. This gives us many explicit examples of Frobenius code which include the well studied Laflamme code. We show that the classical notion of BCH distance can be generalised to all the Frobenius codes that we construct, including the non-linear ones, and show that the algorithm of Berlekamp can be generalised to correct quantum errors within the BCH limit. This gives, for the first time, a family of codes that are neither CSS nor linear for which efficient decoding algorithm exits.

关键词： BCH codes BCH distance Cascading style sheets decoding Error correction codes Joints Laflamme code Linear code Polynomials Quantum computing cyclic codes cyclic stabiliser codes decoding decoding algorithms linear Frobenius codes linear codes linear cyclic codes linear stabiliser codes positive integer quantum communication quantum cyclic code quantum error correction t-Frobenius codes

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Adaptive Kalman Filtering for Closed-Loop Brain-Machine Interface Systems

Adaptive Kalman Filtering for Closed-Loop Brain-Machine Inte...

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5th International IEEE Engineering-in-Medicine-and-Biology-Society (EMBS) Conference on Neural Engineering (NER)

作者： Dangi, Siddharth Gowda, Suraj Heliot, Rodolphe Carmena, Jose M. Univ Calif Berkeley Dept Elect Engn & Comp Sci Berkeley CA 94720 USA

ISBN: (纸本)9781424441419

Brain-Machine Interface (BMI) decoding algorithms are often trained offline, but this paradigm ignores both the non-stationarity of neural signals and the feedback that exists in online, closed-loop control. To address these problems, we have developed an Adaptive Kalman Filter (AKF), a Kalman filter variant that adaptively updates its model parameters during training. For a Kalman filter decoder, batch retraining methods require completely re-estimating the parameter matrices from sufficient data to perform regression accurately, even if only small changes are necessary. Conversely, the AKF is designed to update the decoder parameters continuously and more intelligently. We simulated a population of 41 neurons learning to control a 2D computer cursor. The AKF yielded significantly faster skill acquisition and better robustness to perturbation and neuron loss than a standard Kalman filter with periodic batch retraining.

关键词： AKF BMI decoding Equations Kalman filters Kinematics Mathematical model Neurons Training adaptive Kalman filtering adaptive Kalman filters batch retraining brain-computer interfaces closed loop systems closed-loop brain-machine interface closed-loop control decoding decoding algorithms medical control systems neural signals neurophysiology training

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A UNIVERSAL decoding ALGORITHM FOR t-EC/AUED CODES

A UNIVERSAL DECODING ALGORITHM FOR t-EC/AUED CODES

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2011 IEEE International Conference on Information Theory and Information Security(ICITIS 2011)

作者： Thabit Sultan Mohammed ECE Department Dhofar University.Engineering CollegeP.O.Box 2509211 SalalahOman.

The All Unidirectional Error Detection （AUED） codes are among the ways of guarding against erroneous correction,and a t-Error Correction （EC）/A11 Unidirectional Error Detection （AUED） code can be constructed by appending a single check symbol （P） to a linear t-EC code to achieve the AUED *** a t-EC/AUED code is used to encode information in a transmission side such information need to be decoded at the receiving *** and techniques proposed in literature for constructing t-EC/AUED codes are either come with no decoding algorithm or if a decoding a algorithm is proposed,it lacks the mathematical *** paper adopts a decoding algorithm from the literature and derives a mathematical proof for *** software is also developed and results for the encoding and decoding processes of four different encoding methods are *** on the mathematical proof and the simulation results obtained,this paper claims that the adopted algorithm is a universal decoding algorithm.

关键词： codes error-correction codes t-EC/AUED decoding algorithms

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Beyond the edge of chaos: Amplification and temporal integration by recurrent networks in the chaotic regime

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Physical Review E 2011年第5期84卷 051908-051908页

作者： T. Toyoizumi L. F. Abbott RIKEN Brain Science Institute Wako-shi Saitama 351-0198 Japan

Randomly connected networks of neurons exhibit a transition from fixed-point to chaotic activity as the variance of their synaptic connection strengths is increased. In this study, we analytically evaluate how well a small external input can be reconstructed from a sparse linear readout of network activity. At the transition point, known as the edge of chaos, networks display a number of desirable features, including large gains and integration times. Away from this edge, in the nonchaotic regime that has been the focus of most models and studies, gains and integration times fall off dramatically, which implies that parameters must be fine tuned with considerable precision if high performance is required. Here we show that, near the edge, decoding performance is characterized by a critical exponent that takes a different value on the two sides. As a result, when the network units have an odd saturating nonlinear response function, the falloff in gains and integration times is much slower on the chaotic side of the transition. This means that, under appropriate conditions, good performance can be achieved with less fine tuning beyond the edge, within the chaotic regime.

关键词： CHAOS theory NEURAL transmission VARIANCES NONLINEAR models (Statistics) decoding algorithms

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Simplified Log-MAP decoding with max* Approximation Based on the Jensen Inequality

Simplified Log-MAP Decoding with max* Approximation B...

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21st Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC)

作者： Sybis, Michal Tyczka, Piotr Papaharalabos, Stylianos Mathiopoulos, Panayiotis Takis Poznan Univ Tech Chair Wireless Commun Poznan Poland Natl Observ Athens Inst Space Applicat & Remote Sensing Athens Greece

ISBN: (纸本)9781424480166

In the paper, a modified Log-MAP algorithm based on a novel approximation of the max* operator derived from the Jensen inequality is proposed. In this approach, the max* operation is performed on n >= 2 arguments, thus the recursive calculations are avoided and significant reduction in the number of operations performed per decoding step, as compared with the conventional Log-MAP, is achieved. Simulation results of BER performance for both turbo codes and turbo trellis-coded modulation (TTCM) employing the new algorithm are given, showing the near-optimal performance of the proposed algorithm.

关键词： decoding algorithms Log-MAP algorithm Turbo codes Turbo TCM max* operator reduced-complexity algorithms

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The Highest Expected Reward decoding for HMMs with Application to Recombination Detection

The Highest Expected Reward Decoding for HMMs with Applicati...

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21st Annual Symposium on Combinatorial Pattern Matching

作者： Nanasi, Michal Vinar, Tomas Brejova, Brona Comenius Univ Fac Math Phys & Informat Bratislava 84248 Slovakia

ISBN: (纸本)9783642135088

Hidden Markov models are traditionally decoded by the Viterbi algorithm which finds the highest probability state path in the model. In recent years, several limitations of the Viterbi decoding have been demonstrated, and new algorithms have been developed to address them (Kall et al., 2005;Brejova et al., 2007;Gross et al., 2007;Brown and Truszkowski, 2010). In this paper, we propose a new efficient highest expected reward decoding algorithm (HERD) that allows for uncertainty in boundaries of individual sequence features. We demonstrate usefulness of our approach on jumping HMMs for recombination detection in viral genomes.

关键词： hidden Markov models decoding algorithms recombination detection jumping HMMs

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Adaptive coded apertures: bridging the gap between non-diffractive and diffractive imaging systems

Adaptive coded apertures: bridging the gap between non-diffr...

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Conference on Adaptive Coded Aperture Imaging, Non-Imaging, and Unconventional Imaging Sensor Systems II

作者： Gottesman, Stephen R. Isser, Abraham Gigioli, George W., Jr. Northrop Grumman Elect Syst Linthicum MD 21090 USA

ISBN: (纸本)9780819483140

The design and implementation of adaptive coded apertures (diffraction) has advanced significantly since the first SPIE conference on Adaptive Coded Aperture Imaging and Non-Imaging Sensors held in 2007. Core algorithmic concepts relating to coding and decoding techniques remain steeply based in its non-diffractive design origins. We discuss adaptive coded aperture imaging's current capabilities in light of recent advances as well as methods of improvement for future systems design. The advantages of implementing reconfigurable mask patterns compared to fixed ones will also be discussed, as well as potential improvement in angular resolution by means of reconfigurable masks.

关键词： Adaptive coded apertures decoding algorithms reconfigurable masks angular resolution lensless imaging diffraction random masks URAs MURAs

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