Policy Adjustment in a Dynamic Economic Game

• Published in: PloS one Vol. 1; no. 1; p. e103
• Main Authors: Li, Jian, McClure, Samuel M., King-Casas, Brooks, Read Montague, P.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 20.12.2006; Public Library of Science (PLoS)
• Subjects: Adult; Behavior; Brain; Brain - physiology; Choice learning; Circuits; Computational Biology/Computational Neuroscience; Contingency; Corpus Striatum - physiology; Cortex (frontal); Decision making; Decision Making - physiology; Dopamine; Emotions; Female; Frontal gyrus; Functional magnetic resonance imaging; Game theory; Harvesting; Humans; Laboratories; Learning; Learning - physiology; Magnetic Resonance Imaging; Male; Medical imaging; Medicine; Mental task performance; Models, Economic; Models, Neurological; Models, Psychological; Neostriatum; Neuroimaging; Neurology; Neuroscience/Cognitive Neuroscience; Neurosciences; Operant conditioning; Paradigms; Prefrontal cortex; Prefrontal Cortex - physiology; Reinforcement; Reinforcement (Psychology); Reward; Task complexity; Young Adult; United States > US; Texas
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0000103

Making sequential decisions to harvest rewards is a notoriously difficult problem. One difficulty is that the real world is not stationary and the reward expected from a contemplated action may depend in complex ways on the history of an animal's choices. Previous functional neuroimaging work combined with principled models has detected brain responses that correlate with computations thought to guide simple learning and action choice. Those works generally employed instrumental conditioning tasks with fixed action-reward contingencies. For real-world learning problems, the history of reward-harvesting choices can change the likelihood of rewards collected by the same choices in the near-term future. We used functional MRI to probe brain and behavioral responses in a continuous decision-making task where reward contingency is a function of both a subject's immediate choice and his choice history. In these more complex tasks, we demonstrated that a simple actor-critic model can account for both the subjects' behavioral and brain responses, and identified a reward prediction error signal in ventral striatal structures active during these non-stationary decision tasks. However, a sudden introduction of new reward structures engages more complex control circuitry in the prefrontal cortex (inferior frontal gyrus and anterior insula) and is not captured by a simple actor-critic model. Taken together, these results extend our knowledge of reward-learning signals into more complex, history-dependent choice tasks. They also highlight the important interplay between striatum and prefrontal cortex as decision-makers respond to the strategic demands imposed by non-stationary reward environments more reminiscent of real-world tasks.