Enhanced cortical specialization to distinguish older and newer memories in highly superior autobiographical memory

There is a growing consensus on the role played by the hippocampus and the medial prefrontal cortex in autobiographical memory. However, it is not clear whether and how these key regions play a central role in enabling forms of enhanced memory, such as highly superior autobiographical memory (HSAM). Here, we investigated the role of the hippocampus, the ventromedial (vmPFc) and dorsomedial (dmPFc) prefrontal cortices in discriminating older vs newer autobiographical events in a group of rare individuals with HSAM through multivoxel pattern analysis of functional neuroimaging data. During fMRI scanning, participants with HSAM and normal memory controls were asked to recollect remote and more recent events. We found a stronger neural signature of older vs newer autobiographical memories within the vmPFc of HSAM subjects as compared to controls. In this brain region, the discriminability between the multivariate neural patterns of the two types of memories increased as a function of the temporal distance that separated older and newer events in HSAM subjects. Comparable neural patterns of older vs newer memories were found instead within the dmPFc and hippocampus of both groups. Overall, these findings highlight for the first time that HSAM relies on enhanced vmPFc specialization to represent past experiences, therefore contributing to uncover the neurobiological mechanisms potentially enabling enhanced forms of memory. Implications of the current findings for the extant models of autobiographical memory are discussed.