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 Statistical Learning



Stimulus Evoked Independent Factor Analysis of MEG Data with Large Background Activity

Neural Information Processing Systems

This paper presents a novel technique for analyzing electromagnetic imaging data obtained using the stimulus evoked experimental paradigm. The technique is based on a probabilistic graphical model, which describes thedata in terms of underlying evoked and interference sources, and explicitly models the stimulus evoked paradigm.



Inferring Motor Programs from Images of Handwritten Digits

Neural Information Processing Systems

We describe a generative model for handwritten digits that uses two pairs of opposing springs whose stiffnesses are controlled by a motor program. We show how neural networks can be trained to infer the motor programs required to accurately reconstruct the MNIST digits. The inferred motor programs can be used directly for digit classification, but they can also be used in other ways. By adding noise to the motor program inferred from an MNIST image we can generate a large set of very different images of the same class, thus enlarging the training set available to other methods. We can also use the motor programs as additional, highly informative outputs which reduce overfitting when training a feed-forward classifier.



Nested sampling for Potts models

Neural Information Processing Systems

Nested sampling is a new Monte Carlo method by Skilling [1] intended forgeneral Bayesian computation. Nested sampling provides a robust alternative to annealing-based methods for computing normalizing constants. It can also generate estimates of other quantities such as posterior expectations. The key technical requirement isan ability to draw samples uniformly from the prior subject to a constraint on the likelihood. We provide a demonstration withthe Potts model, an undirected graphical model.



Estimation of Intrinsic Dimensionality Using High-Rate Vector Quantization

Neural Information Processing Systems

We introduce a technique for dimensionality estimation based on the notion ofquantization dimension, which connects the asymptotic optimal quantization error for a probability distribution on a manifold to its intrinsic dimension.The definition of quantization dimension yields a family of estimation algorithms, whose limiting case is equivalent to a recent method based on packing numbers. Using the formalism of high-rate vector quantization, we address issues of statistical consistency and analyze thebehavior of our scheme in the presence of noise.


On the Convergence of Eigenspaces in Kernel Principal Component Analysis

Neural Information Processing Systems

This paper presents a non-asymptotic statistical analysis of Kernel-PCA with a focus different from the one proposed in previous work on this topic. Here instead of considering the reconstruction error of KPCA we are interested in approximation error bounds for the eigenspaces themselves. Weprove an upper bound depending on the spacing between eigenvalues but not on the dimensionality of the eigenspace. As a consequence thisallows to infer stability results for these estimated spaces.


Generalization Error Bounds for Aggregation by Mirror Descent with Averaging

Neural Information Processing Systems

For this purpose, we propose a stochastic procedure, the mirror descent, which performs gradient descent inthe dual space. The generated estimates are additionally averaged in a recursive fashion with specific weights. Mirror descent algorithms havebeen developed in different contexts and they are known to be particularly efficient in high dimensional problems. Moreover their implementation is adapted to the online setting. The main result of the paper is the upper bound on the convergence rate for the generalization error.