Remote Autobiographical Memories Research Articles

Different Patterns of Autobiographical Memory Loss in Semantic Dementia and Medial Temporal Lobe Amnesia: a Challenge to Consolidation Theory.

Temporally graded retrograde memory loss, with a disproportionate impairment of recent relative to remote memories, is considered a hallmark of medial temporal lobe amnesia. According to consolidation theory, the hippocampal complex, which includes the hippocampal formation, parahippocampal gyrus, the entorhinal and perirhinal cortex, plays a time-limited role in memory, needed only until consolidation in the neocortex is complete (Squire, Psychological Review 1992; 99: 195–231). Recent support for this theory comes from findings of a reverse gradient in people with semantic dementia with neocortical degeneration but a relatively preserved hippocampal complex (Hodges and Graham, Neuropsychologia 1998; 36: 803–25). Consolidation theory is challenged by evidence that remote autobiographical memory is not always spared in amnesia (Nadel and Moscovitch, Current Opinion in Neurobiology 1997; 7: 217–27) and that semantic memory becomes highly personalized in semantic dementia (Snowden et al., Memory 1995; 3: 225–46). According to Nadel and Moscovitch, the hippocampal complex is needed to retain and retrieve detailed memories of autobiographical episodes no matter how old they are. To test consolidation theory against the opposing view, we investigated the role of the hippocampal complex in recent and remote autobiographical and personal semantic memory by contrasting the memory of a semantic dementia patient, EL, with that of an amnesic patient, KG, using family photographs as recall cues. KG demonstrated a complete loss of autobiographical episodes with a sparing of autobiographical facts; EL demonstrated well-preserved memory for episodes with a reverse gradient for personally relevant names. The influence of autobiographical significance on memory for names of public figures was examined further by comparing the effect that familiarity and recollection had on recognition of names of famous people and famous places. EL’s memory was influenced by autobiographical significance, whereas KC’s was not. We propose that the hippocampal complex plays a permanent role in the storage and retrieval of autobiographical episodes and that autobiographical significance may affect semantic representations.

Hippocampal complex and retrieval of recent and very remote autobiographical memories: evidence from functional magnetic resonance imaging in neurologically intact people.

It has been argued that the role of the hippocampus in memory is time-limited: during a period of memory consolidation, other brain regions such as the neocortex are said to acquire the ability to support memory retention and retrieval on their own. An alternative view is that retention and retrieval of memory for autobiographical episodes depend on the hippocampal complex, regardless of the age of the memory. We examined the participation of the hippocampal complex in a functional magnetic resonance imaging (fMRI) study in which participants were asked to recollect autobiographical events that occurred either within the last 4 years or more than 20 years ago. We found equivalent levels of hippocampal activation in both conditions in all participants (N = 10). In addition, activation in neocortical regions did not differ as a function of the age of the memory, even though most of the recent memories recalled were less than 2 years old and the remote memories more than 35 years old. The results support the notion that the hippocampal complex participates in retention and recovery of even very old autobiographical memories, and place boundary conditions on theories of memory consolidation.

A Study of Remote Memory Impairment in Alzheimer’s Disease by Using the Family Line Test

We evaluated remote autobiographical memory impairment in 25 patients with probable Alzheimer’s disease (AD) and 25 sex-, age- and education-matched healthy subjects by using a newly developed, highly effective assessment tool for remote memory, the Family Line Test (FLT). The FLT yields a total score, scores for 3 lifetime periods and the duration of remote memory impairment. In the patients with AD, the total score was significantly lower and the duration of remote memory impairment was significantly longer than in the healthy controls. A prominent temporal gradient in remote memory impairment was documented in the patients with AD. The total FLT score and duration of remote memory impairment correlated with recent memory and general cognitive dysfunctions.