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Abstract

Recent experimental studies have focused on the specialization of different neural
structures for different types of instrumental behavior. Recent theoretical work
has provided normative accounts for why there should be more than one control
system, and how the output of different controllers can be integrated. Two par-
ticlar controllers have been identified, one associated with a forward model and
the prefrontal cortex and a second associated with computationally simpler, habit-
ual, actor-critic methods and part of the striatum. We argue here for the normative
appropriateness of an additional, but so far marginalized control system, associ-
ated with episodic memory, and involving the hippocampus and medial temporal
cortices. We analyze in depth a class of simple environments to show that episodic
control should be useful in a range of cases characterized by complexity and in-
ferential noise, and most particularly at the very early stages of learning, long
before habitization has set in. We interpret data on the transfer of control from the
hippocampus to the striatum in the light of this hypothesis.