The Role of the Ventral Tegmental Area in the Extinction of Probabilistic Rewards
Committee ChairFallous, Jean-Marc
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PublisherThe University of Arizona.
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AbstractBecause most of the events in the world are probabilistic and changing, the extinction of probabilistic events that no longer occur is important for survival. Here, we investigated the effect of reward probability on the rate of extinction using behavioral and pharmacological experiments in rats and temporal difference model simulations. Our experimental results suggested that ambiguity during extinction and the value of probabilistic reward are the two major causes that resulted in the inverted U-shaped relationship between the rate of extinction and reward probability. Using pharmacological activation and inactivation of midbrain dopamine neurons, we reasoned that ambiguity may not be signaled by dopamine neurons. By adding an ambiguity signal into an existing temporal difference model, we reproduced the inverted U-shape for the first time and supported our conclusion. Our study provides insights into the extinction of probabilistic rewards and gives a useful computational model for further investigation.
Degree ProgramGraduate College