Although many preferential choices in everyday life require remembering relevant information, the interplay of neural systems mediating decisions and memory has rarely been studied. We addressed this question by combining a task, in which choice options had to be retrieved from memory, with cognitive modeling and fMRI. We found that memory-guided decisions are captured by established process models of choice (sequential sampling models) but constrained by forgetting. People are biased toward remembered options and reject them only if they are very unattractive. Using a Bayesian modeling approach, we determined the posterior probability that options were remembered given the observed choices. This probability correlated with hippocampal activation during encoding. During decision making, the bias toward remembered options was linked to increased connectivity between hippocampus and ventromedial prefrontal cortex. Our results provide insights into the dependency of decisions on memory constraints and show that memory-related activation can be inferred from decisions.
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