On Linking Reinforcement Learning with Unsupervised Learning Cornelius Weber, FIAS presented at Honda HRI, Offenbach, 17 th March 2009

for taking action, we need only the relevant features x y z

unsupervised learning in cortex reinforcement learning in basal ganglia state space actor Doya, 1999

actor state space 1-layer RL model of BG... go left? go right?... is too simple to handle complex input

complex input (cortex)‏ need another layer(s) to pre-process complex data feature detection action selection actor state space

models’ background: - gradient descent methods generalize RL to several layers Sutton&Barto RL book (1998); Tesauro (1992;1995) - reward-modulated Hebb Triesch, Neur Comp 19, (2007), Roelfsema & Ooyen, Neur Comp 17, (2005); Franz & Triesch, ICDL (2007)‏ - reward-modulated activity leads to input selection Nakahara, Neur Comp 14, (2002) - reward-modulated STDP Izhikevich, Cereb Cortex 17, (2007), Florian, Neur Comp 19/6, (2007); Farries & Fairhall, Neurophysiol 98, (2007);... - RL models learn partitioning of input space e.g. McCallum, PhD Thesis, Rochester, NY, USA (1996)‏

sensory input reward action scenario: bars controlled by actions, ‘up’, ‘down’, ‘left’, ‘right’; reward given if horizontal bar at specific position

model that learns the relevant features top layer: SARSA RL lower layer: winner-take-all feature learning both layers: modulate learning by δ RL weights feature weights input action

SARSA with WTA input layer

note: non-negativity constraint on weights Energy function: estimation error of state-action value identities used:

RL action weights feature weights data learning the ‘short bars’ data reward action

short bars in 12x12 average # of steps to goal: 11

RL action weights feature weights input reward 2 actions (not shown)‏ data learning ‘long bars’ data

WTA non-negative weights SoftMax non-negative weights SoftMax no weight constraints

Discussion - simple model: SARSA on winner-take-all network with δ-feedback - learns only the features that are relevant for action strategy - theory behind: derivation of value function estimation (approx.)‏ - non-negative coding aids feature extraction - link between unsupervised- and reinforcement learning - demonstration with more realistic data needed Bernstein Focus Neurotechnology, BMBF grant 01GQ0840 EU project “IM-CLeVeR”, call FP7-ICT Frankfurt Institute for Advanced Studies, FIAS Sponsors

Bernstein Focus Neurotechnology, BMBF grant 01GQ0840 EU project “IM-CLeVeR”, call FP7-ICT Frankfurt Institute for Advanced Studies, FIAS Sponsors thank you...