Episodic memory encoding interferes with reward learning and decreases striatal prediction errors.
Learning is essential for adaptive decision making. The striatum and its dopaminergic inputs are known to support incremental reward-based learning, while the hippocampus is known to support encoding of single events (episodic memory). Although traditionally studied separately, in even simple experiences, these two types of learning are likely to co-occur and may interact. Here we sought to understand the nature of this interaction by examining how incremental reward learning is related to concurrent episodic memory encoding. During the experiment, human participants made choices between two options (colored squares), each associated with a drifting probability of reward, with the goal of earning as much money as possible. Incidental, trial-unique object pictures, unrelated to the choice, were overlaid on each option. The next day, participants were given a surprise memory test for these pictures. We found that better episodic memory was related to a decreased influence of recent reward experience on choice, both within and across participants. fMRI analyses further revealed that during learning the canonical striatal reward prediction error signal was significantly weaker when episodic memory was stronger. This decrease in reward prediction error signals in the striatum was associated with enhanced functional connectivity between the hippocampus and striatum at the time of choice. Our results suggest a mechanism by which memory encoding may compete for striatal processing and provide insight into how interactions between different forms of learning guide reward-based decision making.
Department of Psychology and Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany, and shohamy@psych.columbia.edu elliott@caa.columbia.edu.
G Elliott
http://orcid.org/0000-0002-2227-119X
GE
Wimmer
Department of Psychology and.
Erin Kendall
EK
Braun
Center for Neural Science and Department of Psychology, New York University, New York, New York 10003.
Nathaniel D
ND
Daw
Department of Psychology and Kavli Institute for Brain Science, Columbia University, New York, New York 11027, shohamy@psych.columbia.edu elliott@caa.columbia.edu.
Daphna
D
Shohamy
D000293:Adolescent; D000328:Adult; D001245:Association Learning; D002755:Choice Behavior; D003342:Corpus Striatum / Q000502:physiology*; D005260:Female; D006624:Hippocampus / Q000502:physiology; D006801:Humans; D008297:Male; D061212:Memory, Episodic; D012201:Reward
decision making; hippocampus; learning; memory; reward; striatum