Consolidation of human memory over decades revealed by functional magnetic resonance imaging

Medial temporal lobe (MTL) lesions typically produce retrograde amnesia characterized by the disproportionate loss of recently acquired memories. Temporally graded memory loss is interpreted traditionally as evidence for a consolidation process guided by the MTL. Here, using functional magnetic resonance imaging (fMRI), we show temporally graded changes in MTL activity in healthy older adults taking a famous faces remote memory test. Evidence for temporally graded change in the hippocampal formation was mixed, suggesting it may participate only in consolidation processes lasting a few years. Entorhinal cortex was associated with temporally graded changes extending up to 20 years. These findings support the basic tenets of consolidation theory and suggest that the entorhinal cortex, rather than the hippocampal formation, participates in memory consolidation over decades.