Human retrograde amnesia and memory consolidation.

This paper reports a reassessment of published literature on the question of whether retrograde amnesia data from patients with severe trauma supports the idea that there is ongoing consolidation of long-lasting memories. That is, memory consolidation continues for decades with older memories being increasingly consolidated, and, thus, more protected from forgetting. Our analysis was limited to patients with specific traumas rather than neurodegenerative conditions that can be complicated by the additional presence of significant anterograde amnesia. These constraints were used because trauma patients have a definitive start to their amnesia allowing comparison of their memories before this event, unlike when there is an undefined amnesia onset. Our results revealed that the standard account of retrograde amnesia only fits part of the data, with more than half not conforming to this account. Specifically, damage to different brain areas was associated with different patterns of retrograde amnesia. Those cases where the standard retrograde amnesia account was held tended to involve damage to the hippocampus and temporal lobes, as expected. Future directions to better understand the influence of retrograde amnesia and memory consolidation are suggested.