Echoes of time. Organization of episodic autobiographical memories in the brain according to their remoteness

: Autobiographical memories enable us to "navigate" our personal past, although how the brain organizes them over extended time periods remains unclear. Using task-based fMRI and decoding analysis we found that a distributed network of areas in the brain, including medial temporal lobes, posterior parietal cortex, prefrontal regions, and visual association areas, distinguished memory age. The analysis of representational similarity matrices suggested that different regions contributed to the representation of the identity of unique events or their temporal representation. The right hippocampus encoded both fine-grained identity and temporal structure, whereas the frontopolar and retrosplenial cortices selectively encoded temporal structure. Representational connectivity analysis confirmed the robust inter-correlations within the right medial temporal lobe and prefrontal/retrosplenial cortex. These findings support the existence of a temporally organized mnemonic schema, namely a neural "timeline", that underlies our ability to situate and differentiate personal memories across the lifespan.