Memory is essential for adaptive behavior. Conscious access to the past improves our ability to make accurate predictions about the future and to engage in intelligent goal-directed behavior. In order for memory to be adaptive, incoming sensory representations must be stored flexibly in the brain so they can be recalled under varying cognitive conditions and used to guide diverse behavioral repertoires. While some of the brain regions critical for episodic memory have been identified, the mechanisms that transform perceptual experiences into flexible memory representations are not well understood.

The experiments in this thesis were designed to characterize the hippocampal and neocortical mechanisms that shape simple visual experiences into adaptive memories. In these experiments, human subjects were exposed to visual stimuli and then later asked to remember them. Functional magnetic resonance imaging was used to measure the neural representation of perceived and remembered stimuli under different cognitive conditions. In the first chapter, I test whether interference resolution mechanisms in the hippocampus adapt to experience. I demonstrate that the hippocampus resolves competition during learning by minimizing neural overlap between perceptually similar stimuli. I show that this benefits behavior by reducing memory interference when these stimuli are encountered again. In the second chapter, I characterize the role of the lateral parietal cortex in flexibly retrieving memories. I show that lateral parietal cortex representations are stronger for remembered than perceived visual stimuli, opposing the bias seen in visual cortex. Further, I show that memory representations in dorsal parietal regions are biased toward stimulus features that align with retrieval goals. In the final chapter, I quantify how stimulus-triggered activity in the visual system differs from memory-triggered activity. I show that while memory-triggered activity is retinotopically mapped, even in the earliest visual areas, memory activity is also transformed by spatial pooling in the visual system during perception. Together, the results of these experiments provide insight into how experience, goals, and intrinsic neural organization shape the way that visual stimuli come to be stored in the brain long-term.