Connectionists: New Paper

[Arjen van Ooyen]

Attention-Gated Reinforcement Learning of Internal Representations for 
Classification

Pieter R. Roelfsema & Arjen van Ooyen, Neural Computation (2005) 17: 
2176-2214.


Abstract

Animal learning is associated with changes in the efficacy of 
connections between neurons. The rules that govern this plasticity can 
be tested in neural networks. Rules that train neural networks to map 
stimuli onto outputs are given by supervised learning and reinforcement 
learning theories. Supervised learning is efficient but biologically 
implausible. In contrast, reinforcement learning is biologically 
plausible but comparatively inefficient. It lacks a mechanism that can 
identify units at early processing levels that play a decisive role in 
the stimulus-response mapping. Here we show that this so-called credit 
assignment problem can be solved by a new role for attention in 
learning. There are two factors in our new learning scheme that 
determine synaptic plasticity: (1) a reinforcement signal that is 
homogeneous across the network and depends on the amount of reward 
obtained after a trial, and (2) an attentional feedback signal from the 
output layer that limits plasticity to those units at earlier processing 
levels that are crucial for the stimulus-response mapping. The new 
scheme is called attention-gated reinforcement learning (AGREL). We show 
that it is as efficient as supervised learning in classification tasks. 
AGREL is biologically realistic and integrates the role of feedback 
connections, attention effects, synaptic plasticity, and reinforcement 
learning signals into a coherent framework.


For full text, go to 
http://www.bio.vu.nl/enf/vanooyen/papers/agrel2005_abstract.html



-- 
Dr. Arjen van Ooyen
Center for Neurogenomics and Cognitive Research (CNCR)
Department of Experimental Neurophysiology
Vrije Universiteit
De Boelelaan 1085
1081 HV Amsterdam
The Netherlands

E-mail: arjen.van.ooyen at falw.vu.nl
Phone:  +31.20.5987090
Fax:    +31.20.5987112
Room:   B329
Web:    http://www.bio.vu.nl/enf/vanooyen