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The Ising decoder: reading out the activity of large neural ensembles

JOURNAL OF COMPUTATIONAL NEUROSCIENCE 2012年第1期32卷 101-118页

作者： Schaub, Michael T. Schultz, Simon R. Univ London Imperial Coll Sci Technol & Med Dept Bioengn London SW7 2AZ England

The Ising model has recently received much attention for the statistical description of neural spike train data. In this paper, we propose and demonstrate its use for building decoders capable of predicting, on a millisecond timescale, the stimulus represented by a pattern of neural activity. After fitting to a training dataset, the Ising decoder can be applied "online" for instantaneous decoding of test data. While such models can be fit exactly using Boltzmann learning, this approach rapidly becomes computationally intractable as neural ensemble size increases. We show that several approaches, including the Thouless-Anderson-Palmer (TAP) mean field approach from statistical physics, and the recently developed Minimum Probability Flow Learning (MPFL) algorithm, can be used for rapid inference of model parameters in large-scale neural ensembles. Use of the Ising model for decoding, unlike other problems such as functional connectivity estimation, requires estimation of the partition function. As this involves summation over all possible responses, this step can be limiting. Mean field approaches avoid this problem by providing an analytical expression for the partition function. We demonstrate these decoding techniques by applying them to simulated neural ensemble responses from a mouse visual cortex model, finding an improvement in decoder performance for a model with heterogeneous as opposed to homogeneous neural tuning and response properties. Our results demonstrate the practicality of using the Ising model to read out, or decode, spatial patterns of activity comprised of many hundreds of neurons.

关键词： Neural coding decoding algorithm Brain machine interface Brain computer interface BCI Correlations Synchrony Visual cortex Spatial patterns

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A novel region graph construction based on trapping sets for the Generalized Belief Propagation

A novel region graph construction based on trapping sets for...

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IEEE International Conference on Communication Systems (ICCS)

作者： Sibel, Jean-Christophe Reynal, Sylvain Declercq, David Univ Cergy Pontoise ENSEA ETIS CNRSINRIAUMR 8051 Cergy Pontoise France Univ Cergy Pontoise CNRS UMR 8051 ETIS ENSEA Cergy Pontoise France

ISBN: (纸本)9781467320542;9781467320528

The Belief Propagation (BP) is an inference algorithm used to estimate marginal probability distributions for any Markov Random Field (MRF). In the realm of Low-Density Parity-Check (LDPC) codes that can be represented by MRF called Tanner graphs, the BP is used as a decoding algorithm to estimate the states of bits sent through a noisy channel. Known to be optimal when the Tanner graph is a tree, the BP suffers from suboptimality when the Tanner graph has a loop-like topology. Furthermore, combinations of loops, namely the trapping sets, are particularly harmful for the decoding. To circumvent this problem were proposed other algorithms, like the Generalized Belief Propagation (GBP) that comes from statistical physics. This algorithm allows to absorb topological structures inside new nodes called regions. An advantage is that the resulting graph, the region graph, is not unique then according to its construction this region graph is a media for the GBP that can provide more accurate estimates than the BP. In this paper, we propose novel constructions of the region graph for the famous Tanner code of length N = 155 by making use of the trapping sets as basis for the regions.

关键词： trapping sets Belief propagation Line graph noisy channel Inference algorithms Probability distribution decoding algorithm

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On a Construction of Universal Network Code using LDPC Matrices

On a Construction of Universal Network Code using LDPC Matri...

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IEEE International Symposium on Information Theory

作者： Miyake, Shigeki Muramatsu, Jun Nippon Telegraph & Tel Corp Network Innovat Labs 1-1 Hikarinooka Yokosuka Kanagawa Japan

ISBN: (纸本)9781467325790

An LDPC matrix is used as a local encoding kernel at each link to construct a universal code to address network coding problems. It is also shown that at each terminal node the global encoding kernel that constructs a decoder becomes an LDPC matrix. This provides the perspective that decoding complexity can be reduced to a linear order of a block length by using an efficient decoding algorithm such as the sum-product algorithm.

关键词： universal coding Sum-product algorithm decoding algorithm decoders Perspective end node Codes

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Solving Multidimensional 0-1 Knapsack Problem with an Artificial Fish Swarm algorithm

Solving Multidimensional 0-1 Knapsack Problem with an Artifi...

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12th International Conference on Computational Science and Its Applications (ICCSA)

作者： Azad, Md. Abul Kalam Rocha, Ana Maria A. C. Fernandes, Edite M. G. P. Univ Minho Algoritmi R&D Ctr P-4710057 Braga Portugal

ISBN: (纸本)9783642311369;9783642311376

The multidimensional 0-1 knapsack problem is a combinatorial optimization problem, which is NP-hard and arises in many fields of optimization. Exact as well as heuristic methods exist for solving this type of problem. Recently, a population-based artificial fish swarm algorithm was proposed and applied in an engineering context. In this paper, we present a binary version of the artificial fish swarm algorithm for solving multidimensional 0-1 knapsack problem. Infeasible solutions are made feasible by a decoding algorithm. We test the presented method with a set of benchmark problems and compare the obtained results with other methods available in literature. The tested method appears to give good results when solving these problems.

关键词： 0-1 knapsack problem multiple constraints artificial fish swarm decoding algorithm

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Hardware Complexities of Low-Complexity Chase Reed Solomon Decoders and Comparisons

Hardware Complexities of Low-Complexity Chase Reed Solomon D...

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IEEE Asia Pacific Conference on Circuits and Systems (APCCAS)

作者： Wang, Hao Zhang, Wei Wang, Jing Jiang, Zhe Tianjin Univ Sch Elect Informat Engn Tianjin 300072 Peoples R China

ISBN: (纸本)9781457717284;9781457717291

Reed-Solomon (RS) codes are widely used in digital communication and storage systems. Algebraic soft-decision decoding (ASD) of RS codes can achieve significant coding gain over the hard-decision decoding (HDD). Compared with other ASD algorithms, the low-complexity Chase (LCC) decoding algorithm needs less computation complexity with similar or higher coding gain. Several techniques have been applied to reduce the decoding complexity and made the LCC decoding algorithm easier to be implemented by hardware. This paper answers the question that which practical LCC decoder is the most efficient. In addition, decoder complexity comparisons for an example (255, 239) RS code constructed over GF(2(8)) are presented. This paper also provides discussions on how the hardware complexities of LCC decoders change with the decoding parameter and code rate.

关键词： Reed-Solomon codes decoders coding gain Digital communication code rate Computer hardware Cache Memory System Solomon decoding algorithm Reed heart atrium septum defect

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An Adaptive Conditional Zero-Forcing Decoder with Full-diversity, Least Complexity and Essentially-ML Performance for STBCs

An Adaptive Conditional Zero-Forcing Decoder with Full-diver...

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International Symposium on Information Theory and its Applications (ISITA)

作者： Natarajan, Lakshmi Prasad Rajan, B. Sundar IISc Dept ECE Bangalore 560012 Karnataka India

ISBN: (纸本)9784885522673

A low complexity decoding technique with an essentially-ML performance for the Golden code and the 3 antenna Perfect code was introduced by Sirianunpiboon, Howard & Calderbank. Though no theoretical analysis of the decoder was given, the simulations showed that this decoding technique has almost maximum-likelihood (ML) performance. Inspired by this technique, in this paper we introduce two new low complexity decoders for Space-Time Block Codes (STBCs) - the Adaptive Conditional Zero-Forcing (ACZF) decoder and the ACZF decoder with successive interference cancellation (ACZF-SIC), which include as a special case the decoding technique of Sirianunpiboon et al. We show that both ACZF and ACZF-SIC decoders are capable of achieving full-diversity under Rayleigh fading, and we give sufficient conditions for an STBC to give full-diversity with these decoders. We then show that the Golden code, the 3 and 4 antenna Perfect codes, the 3 antenna Threaded Algebraic Space-Time code and the 4 antenna rate 2 code of Srinath & Rajan are all full-diversity ACZF/ACZF-SIC decodable with complexity strictly less than that of their ML decoders. Simulations show that the proposed decoding method performs identical to ML decoding for all these five codes. These STBCs along with the proposed decoding algorithm outperform all known codes in terms of both decoding complexity and error performance for N-t <= 4 transmit antennas. We further provide a lower bound on the complexity of full-diversity ACZF/ACZF-SIC decoding. The proposed decoders for all the five codes listed above achieve this lower bound and hence are optimal in terms of minimizing the ACZF/ACZF-SIC decoding complexity.

关键词： decoders decoding space time block coding Codes Computer Programming Languages Complexity decoding algorithm ANTENNA antennae simulating error performance

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Efficient Termination of Spatially-Coupled Codes

Efficient Termination of Spatially-Coupled Codes

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IEEE Information Theory Workshop (ITW)

作者： Tazoe, Koji Kasai, Kenta Sakaniwa, Kohichi Tokyo Inst Technol Dept Commun & Integrated Syst Tokyo 1528550 Japan

ISBN: (纸本)9781467302234

Spatially-coupled low-density parity-check codes attract much attention due to their capacity-achieving performance and a memory-efficient sliding-window decoding algorithm. On the other hand, the encoder needs to solve large linear equations to terminate the encoding process. In this paper, we propose modified spatially-coupled codes. The modified (d(l), d(r), L) codes have less rate-loss, i.e., higher coding rate, and have the same threshold as (d(l), d(r), L) codes and are efficiently terminable by using an accumulator.

关键词： Codes Linear equation accumulator stopping sliding windows low density parity check codes decoding algorithm

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Left-to-Right Tree-to-String decoding with Prediction 12

Left-to-Right Tree-to-String Decoding with Prediction

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Conference on Empirical Methods in Natural Language Processing

作者： Yang Feng Yang Liu Qun Liu Trevor Cohn Department of Computer Science The University of Sheffield Sheffield UK State Key Laboratory on Intelligent Technology and Systems Tsinghua National Laboratory for Information Science and Technology Department of Computer Sci. and Tech. Tsinghua University Beijing China Key Laboratory of Intelligent Information Processing Institute of Computing Technology Chinese Academy of Sciences Beijing China

ISBN: (纸本)9781622765034

decoding algorithms for syntax based machine translation suffer from high computational complexity, a consequence of intersecting a language model with a context free grammar. Left-to-right decoding, which generates the target string in order, can improve decoding efficiency by simplifying the language model evaluation. This paper presents a novel left to right decoding algorithm for tree-to-string translation, using a bottom-up parsing strategy and dynamic future cost estimation for each partial translation. Our method outperforms previously published tree-to-string decoders, including a competing left-to-right method.

关键词： modelling languages decoding decoding algorithm machine translation syntax context-free grammars

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Generalized Higher-Order Dependency Parsing with Cube Pruning 12

Generalized Higher-Order Dependency Parsing with Cube Prunin...

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Conference on Empirical Methods in Natural Language Processing

作者： Hao Zhang Ryan McDonald Google Inc.

ISBN: (纸本)9781622765034

State-of-the-art graph-based parsers use features over higher-order dependencies that rely on decoding algorithms that are slow and difficult to generalize. On the other hand, transition-based dependency parsers can easily utilize such features without increasing the linear complexity of the shift-reduce system beyond a constant. In this paper, we attempt to address this imbalance for graph-based parsing by generalizing the Eisner (1996) algorithm to handle arbitrary features over higher-order dependencies. The generalization is at the cost of asymptotic efficiency. To account for this, cube pruning for decoding is utilized (Chiang, 2007). For the first time, label tuple and structural features such as valencies can be scored efficiently with third-order features in a graph-based parser. Our parser achieves the state-of-art unlabeled accuracy of 93.06% and labeled accuracy of 91.86% on the standard test set for English, at a faster speed than a reimplementation of the third-order model of Koo et al. (2010).

关键词： Parser Parsing decoding Cube higher-order test standards tree surgery Structural properties English Valence English language Generalization fast speed decoding algorithm

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Sublinear Time, Measurement-Optimal, Sparse Recovery For All 12

Sublinear Time, Measurement-Optimal, Sparse Recovery For All

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Annual ACM-Society for Industrial and Applied Mathmatics Symposium on Discrete algorithms

作者： Ely Porat Martin J. Strauss Bar Ilan University University of Michigan

ISBN: (纸本)9781611972108

An approximate sparse recovery system in l_1 norm makes a small number of measurements of a noisy vector with at most k large entries and recovers those heavy hitters approximately. Formally, it consists of parameters N, k, ε, an m-by-N measurement matrix, φ, and a decoding algorithm, D. Given a vector, x, where x_k denotes the optimal k-term approximation to x, the system approximates x by {top}x = D(φx), which must satisfy ‖x{top}^ - x‖_1 ≤ (1 + ε) ‖x - x_k‖_1. Among the goals in designing such systems are minimizing the number m of measurements and the runtime of the decoding algorithm, D. We consider the "forall" model, in which a single matrix φ, possibly "constructed" non-explicitly using the probabilistic method, is used for all signals x.

关键词： decoding algorithm sublinear system recovery mechanical heart valve K CORRECTION Runtime measurement matrix deuterium ABSORBED DOSE

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