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Limited By:	Author = Jaramillo, Santiago ;

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Displaying Results 1 - 7 of 7 on page 1 of 1

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A normative model of attention: receptive field modulation (2004)

Jaramillo, Santiago; Pearlmutter, Barak A.

A normative model of attention: receptive field modulation (2004)

Jaramillo, Santiago; Pearlmutter, Barak A.

Abstract:

When sensory stimuli are encoded in a lossy fashion for efficient transmission, there are necessarily tradeoffs between the represented fidelity of various aspects of the stimuli. In the model of attention presented here, a top-down signal informs the encoder of these tradeoffs. Given the stimulus ensemble and tradeoff requirements, our system learns an optimal encoder. This general model is instantiated in a simple network: an autoencoder with a bottleneck, innervated by a top-down attentional signal, and trained using backpropagation. The modulation of neural activity learned by this model qualitatively matches that measured in animals during visual attention tasks.

http://mural.maynoothuniversity.ie/8120/

Marked Mark

Allocation of Computational Resources in the Nervous System. (2006)

Jaramillo, Santiago

Allocation of Computational Resources in the Nervous System. (2006)

Jaramillo, Santiago

Abstract:

The nervous system integrates past information together with predictions about the future in order to produce rewarding actions for the organism. This dissertation focuses on the resources underlying these computations, and the task-dependent allocation of these resources. We present evidence that principles from optimal coding and optimal estimation account for overt and covert orienting phenomena, as observed from both behavioral experiments and neuronal recordings. First, we review behavioral measurements related to selective attention and discuss models that account for these data. We show that reallocation of resources emerges as a natural property of systems that encode their inputs efficiently under non-uniform constraints. We continue by discussing the attentional modulation of neuronal activity, and showthat: (1) Modulation of coding strategies does not require special mechanisms: it is possible to obtain dramatic modulation even when signals informing the system about fid...

http://mural.maynoothuniversity.ie/1765/

Marked Mark

Attention and Optimal Sensory Codes (2004)

Jaramillo, Santiago; Pearlmutter, Barak A.

Attention and Optimal Sensory Codes (2004)

Jaramillo, Santiago; Pearlmutter, Barak A.

Abstract:

Neuronal activity can be modulated by attention even while the sensory stimulus is held fixed. This modulation implies changes in the tuning curve (or receptive field) of the neurons involved in sensory processing. We propose an information-theoretic hypothesis for the purpose of this modulation, and show using computer simulation that the similar modulation emerges in a system that is optimally encoding a sensory stimulus when the system is informed about the changing relevance of different features of the input. We present a simple model that learns a covert attention mechanism, given input patterns and tradeoff requirements. After optimization, the system gains the ability to reorganize its computational resources (or coding strategy) depending on the incoming covert attentional signal, using only threshold shifts in neurons throughout the network. The modulation of activity of the encoding units for different attentional states qualitatively matches that observed in animal selec...

http://mural.maynoothuniversity.ie/1882/

Marked Mark

Brightness Illusions as Optimal Percepts - Technical Report: NUIM-CS-TR-2006-02 (2006)

Jaramillo, Santiago ; Pearlmutter, Barak A.

Brightness Illusions as Optimal Percepts - Technical Report: NUIM-CS-TR-2006-02 (2006)

Jaramillo, Santiago ; Pearlmutter, Barak A.

Abstract:

We show that Mach bands and a number of other low-level brightness illusions can be accounted for by assuming that the perceptual system performs simple Bayesian inference using a Gaussian image prior with noisy retinal gangion cells. This theory accounts for phenomena which have proven problematic for simple energy-based and lateral-interaction models while avoiding the complexities of mid-level vision theories that involve the estimation of structure and albedo.

http://mural.maynoothuniversity.ie/2315/

Marked Mark

Optimal Coding Predicts Attentional Modulation of Activity in Neural Systems (2007)

Jaramillo, Santiago; Pearlmutter, Barak A.

Optimal Coding Predicts Attentional Modulation of Activity in Neural Systems (2007)

Jaramillo, Santiago; Pearlmutter, Barak A.

Abstract:

Neuronal activity in response to a fixed stimulus has been shown to change as a function of attentional state, implying that the neural code also changes with attention. We propose an information-theoretic account of such modulation: that the nervous system adapts to optimally encode sensory stimuli while taking into account the changing relevance of different features. We show using computer simulation that such modulation emerges in a coding system informed about the uneven relevance of the input features. We present a simple feedforward model that learns a covert attention mechanism, given input patterns and coding fidelity requirements. After optimization, the system gains the ability to reorganize its computational resources (and coding strategy) depending on the incoming attentional signal, without the need of multiplicative interaction or explicit gating mechanisms between units. The modulation of activity for different attentional states matches that observed in a variety of...

http://mural.maynoothuniversity.ie/1307/

Marked Mark

Progress in Blind Separation of Magnetoencephalographic Data (2003)

Pearlmutter, Barak A.; Jaramillo, Santiago

Progress in Blind Separation of Magnetoencephalographic Data (2003)

Pearlmutter, Barak A.; Jaramillo, Santiago

Abstract:

The match between the physics of MEG and the assumptions of the most well developed blind source separation (BSS) algorithms (unknown instantaneous linear mixing process, many sensors compared to expected recoverable sources, large data limit) have tempted researchers to apply these algorithms to MEG data. We review some of these efforts, with particular emphasis on our own work.

http://mural.maynoothuniversity.ie/8140/

Marked Mark

Use your powers wisely: resource allocation in parallel channels (2006)

Pearlmutter, Barak A.; Jaramillo, Santiago

Use your powers wisely: resource allocation in parallel channels (2006)

Pearlmutter, Barak A.; Jaramillo, Santiago

Abstract:

This study evaluates various resource allocation strategies for simultaneous estimation of two independent signals from noisy observations. We focus on strategies that make use of the underlying dynamics of each signal, exploiting the difference in estimation uncertainty between them. This evaluation is done empirically, by exploring the parameter space through computer simulations. Two cases are studied: one in which an initial allocation is maintained during estimation of the variables, and one in which allocation can be dynamically changed at each time step according to the uncertainty of the estimate from each channel. The results suggest that there are conditions in which it is advantageous to assign a high signal-to-noise ratio (SNR) to only one of the signals and guess the other one. Furthermore, comparison between the two allocation strategies shows that the dynamic strategy significantly improves estimation performance in low SNR scenarios when the signals have similar dyna...

http://mural.maynoothuniversity.ie/1361/

Displaying Results 1 - 7 of 7 on page 1 of 1