Over a century ago, Freud proposed that unwanted memories can be excluded from awareness, a process called repression. It is unknown, however, how repression occurs in the brain. We used functional magnetic resonance imaging to identify the neural systems involved in keeping unwanted memories out of awareness. Controlling unwanted memories was associated with increased dorsolateral prefrontal activation, reduced hippocampal activation, and impaired retention of those memories. Both prefrontal cortical and right hippocampal activations predicted the magnitude of forgetting. These results confirm the existence of an active forgetting process and establish a neurobiological model for guiding inquiry into motivated forgetting.

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Remembering often requires the selection of goal-relevant memories in the face of competition from irrelevant memories. Although there is a cost of selecting target memories over competing memories (increased forgetting of the competing memories), here we report neural evidence for the adaptive benefits of forgetting--namely, reduced demands on cognitive control during future acts of remembering. Functional magnetic resonance imaging during selective retrieval showed that repeated retrieval of target memories was accompanied by dynamic reductions in the engagement of functionally coupled cognitive control mechanisms that detect (anterior cingulate cortex) and resolve (dorsolateral and ventrolateral prefrontal cortex) mnemonic competition. Strikingly, regression analyses revealed that this prefrontal disengagement tracked the extent to which competing memories were forgotten; greater forgetting of competing memories was associated with a greater decline in demands on prefrontal cortex during target remembering. These findings indicate that, although forgetting can be frustrating, memory might be adaptive because forgetting confers neural processing benefits.

Remembering a past event involves reactivation of content-specific patterns of neural activity in high-level perceptual regions (e.g., ventral temporal cortex, VTC). In contrast, the subjective experience of vivid remembering is typically associated with increased activity in lateral parietal cortex (LPC)-"retrieval success effects" that are thought to generalize across content types. However, the functional significance of LPC activation during memory retrieval remains a subject of active debate. In particular, theories are divided with respect to whether LPC actively represents retrieved content or if LPC activity only scales with content reactivation elsewhere (e.g., VTC). Here, we report a human fMRI study of visual memory recall (faces vs scenes) in which complementary forms of multivoxel pattern analysis were used to test for and compare content reactivation within LPC and VTC. During recall of visual images, we observed robust reactivation of broad category information (face vs scene) in both VTC and LPC. Moreover, recall-related activity patterns in LPC, but not VTC, differentiated between individual events. Importantly, these content effects were particularly evident in areas of LPC (namely, angular gyrus) in which activity scaled with subjective reports of recall vividness. These findings provide striking evidence that LPC not only signals that memories have been successfully recalled, but actively represents what is being remembered.