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Solving the Distal Reward Problem through Linkage of STDP and Dopamine Signaling

Summary: Solving the Distal Reward Problem through
Linkage of STDP and Dopamine Signaling
Eugene M. Izhikevich
The Neurosciences Institute, 10640 John Jay Hopkins Drive,
San Diego, CA 92121, USA
In Pavlovian and instrumental conditioning, reward typically comes
seconds after reward-triggering actions, creating an explanatory
conundrum known as ``distal reward problem'': How does the brain
know what firing patterns of what neurons are responsible for the
reward if 1) the patterns are no longer there when the reward
arrives and 2) all neurons and synapses are active during the
waiting period to the reward? Here, we show how the conundrum
is resolved by a model network of cortical spiking neurons with
spike-timing--dependent plasticity (STDP) modulated by dopamine
(DA). Although STDP is triggered by nearly coincident firing
patterns on a millisecond timescale, slow kinetics of subsequent
synaptic plasticity is sensitive to changes in the extracellular DA
concentration during the critical period of a few seconds. Random
firings during the waiting period to the reward do not affect STDP
and hence make the network insensitive to the ongoing activity--


Source: Andrzejak, Ralph Gregor - Departament de Tecnologia, Universitat Pompeu Fabra


Collections: Computer Technologies and Information Sciences