Autobiographical memory includes the retrieval of personal semantic data and the remembrance
of incident or episodic memories. In retrograde amnesias, it has been observed that
recall of autobiographical memories of recent events is poorer than recall of remote
memories. Alzheimer's disease (AD) may also be associated with a temporal gradient
(TG) in memory decline, though studies have yielded inconsistent results on this point.
They have also yielded inconsistent results on whether AD might differentially affect
semantic and episodic remembrance. Here, we compared autobiographical memory of childhood,
early adulthood, and recent life among healthy control (HC) subjects, patients with
early AD, and patients with amnesic mild cognitive impairment (aMCI). Both the aMCI
and AD patients exhibited declines in recall of autobiographical incidents and semantic
information. In AD patients, both components of autobiographical memory had a clear
TG, with better preservation of memories of childhood than those of early adulthood
and recent life. The TG of autobiographical memory decline in AD patients is more
compatible with the Cortical Reallocation Theory than with the Multiple Trace Theory
of memory consolidation. In contrast to AD patients, aMCI patients exhibited impaired
recall of personal facts and autobiographical incidents relating only to recent life.
The significant decline in autobiographical memory for recent life that occurred in
aMCI patients suggests that deterioration of consolidation of personal facts and events
begins with commencement of functional impairment in the hippocampus.