Two years later – Revisiting autobiographical memory representations in vmPFC and hippocampus

• Published in: Neuropsychologia Vol. 110; pp. 159 - 169
• Main Authors: Bonnici, Heidi M., Maguire, Eleanor A.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2018; Pergamon Press
• Subjects: Adult; Aging - physiology; Aging - psychology; Autobiographical memory; Brain Mapping; Consolidation; Female; Hippocampus; Hippocampus - diagnostic imaging; Hippocampus - physiology; Humans; Longitudinal; Longitudinal Studies; Magnetic Resonance Imaging; Male; Memory Consolidation - physiology; Memory, Episodic; MVPA; Prefrontal Cortex - diagnostic imaging; Prefrontal Cortex - physiology; Time Factors; vmPFC; Young Adult; Consolidation; Longitudinal; Hippocampus; MVPA; vmPFC; Autobiographical memory
• ISSN: 0028-3932; 1873-3514
• DOI: 10.1016/j.neuropsychologia.2017.05.014

A long-standing question in memory neuroscience concerns how and where autobiographical memories of personal experiences are represented in the brain. In a previous high resolution multivoxel pattern analysis fMRI study, we examined two week old (recent) and ten year old (remote) autobiographical memories (Bonnici et al., 2012, J. Neurosci. 32:16982–16991). We found that remote memories were particularly well represented in ventromedial prefrontal cortex (vmPFC) compared to recent memories. Moreover, while both types of memory were represented within anterior and posterior hippocampus, remote memories were more easily distinguished in the posterior portion. These findings suggested that a change of some kind had occurred between two weeks and ten years in terms of where autobiographical memories were represented in the brain. In order to examine this further, here participants from the original study returned two years later and recalled the memories again. We found that there was no difference in the detectability of memory representations within vmPFC for the now 2 year old and 12 year old memories, and this was also the case for the posterior hippocampus. Direct comparison of the two week old memories (original study) with themselves two years later (present study) confirmed that their representation within vmPFC had become more evident. Overall, this within-subjects longitudinal fMRI study extends our understanding of autobiographical memory representations by allowing us to narrow the window within which their consolidation is likely to occur. We conclude that after a memory is initially encoded, its representation within vmPFC has stablised by, at most, two years later. •We studied patterns of fMRI activity associated with autobiographical memories.•We focussed in particular on vmPFC and posterior hippocampus.•These brain regions preferentially supported remote autobiographical memories.•Our longitudinal study showed this effect was apparent two years after encoding.•A memory was supported by different neural populations in the hippocampus as it aged.