Retrieval of autobiographical memory in Alzheimer's disease: Relation to volumes of medial temporal lobe and other structures

Abstract

The representation of autobiographical memory is distributed over a network of brain structures, with the medial temporal lobe (MTL) at its epicenter. Some believe that, over time, all memories become independent of their MTL component ("consolidation theories"). Others have suggested that this is true only of semantic memory, while episodic aspects of autobiographical memories are dependent on the MTL for as long as they exist, such as multiple trace theory (MTT). In the present study, the volumes of 28 brain regions, including the MTL, and their relation to autobiographical memory were investigated in a group of patients with Alzheimer's disease with varying degrees of retrograde memory loss as assessed by the Autobiographical Memory Interview (AMI). We used the multivariate analysis method of partial least squares (PLS) to assess patterns of atrophy that can lead to retrograde amnesia. We found that different aspects of autobiographical memory were associated with different patterns of tissue loss. Personal semantics were related to a pattern of bilateral anterior and posterior lateral temporal cortex degeneration, more pronounced on the left, as well as right frontal degeneration. Autobiographical event memory ("episodic") was associated with combined atrophy in bilateral MTL and anterior lateral temporal neocortex, more pronounced on the right. This pattern was invariant for memories from childhood, early adulthood, and recent memories, in line with the predictions of MTT, suggesting that MTL tissue is crucial for retrieval of episodic memories regardless of their age.

Retrograde amnesia in patients with hippocampal, medial temporal, temporal lobe, or frontal pathology

“…Significant correlations with medial temporal lobe volume were found only in the diencephalic group, in whom they were thought to reflect the distal effects of thalamic changes, but not in patients whose principal pathology was in the temporal lobes (herpes encephalitis and hypoxic cases). This latter finding was inconsistent with one of the main predictions of multiple trace theory (but see Gilboa et al 2005). Other observations failed to support consolidation theory, suggesting again that the empirical evidence does not appear to lend full support to either of these theories (Kopelman et al 2003).…”

“…The correlational analyses, in which there was only limited evidence for an association between autobiographical memory scores and medial temporal lobe volumes, also failed to support the predictions of MTT (cf. the findings of Kopelman et al 2003 in a differing set of patients of focal lesion patients, but see Gilboa et al 2005 in Alzheimer patients).…”

Personal semantics: at the crossroads of semantic and episodic memory

“…In a series of studies using sentence verification, Maguire and colleagues reported that, even though PS and GS-related activations overlapped in lateral temporal and medial prefrontal regions [Brodmann area (BA) 10], the PS condition showed greater activation relative to GS in a left-lateralized network including the medial prefrontal cortex, retrosplenial cortex, temporal pole, and temporoparietal junction [21,22]. A concordant structural MRI study in Alzheimer's patients reported a correlation between temporopolar volumes (especially on the left side) and PS as measured by the AMI [23]. Autobiographical facts are typically relatively idiosyncratic (e.g., I know that my brother owns an old blue station wagon), which is compatible with the presumed role of the temporal pole in the retrieval of information associated with unique objects and individuals (e.g., [24,25]).…”

Episodic retrieval and the cortical binding of relational activity

“…Analyses of regions within the PFC suggest that the ventrolateral PFC is involved in the maintenance of item features, semantic access, and initiating retrieval, whereas the dorsolateral PFC is involved in updating and manipulating retrieved features and in more complex or higher-order goaldirected retrievals (see Badre, 2008;Bunge, 2004;Christoff & Gabrieli, 2000;Raposo, Han, & Dobbins, 2009;Wagner, 2002). The MTL also contributes to retrieval, presumably by accessing and activating event features through relational bindings (Eldridge, Engel, Zeineh, Bookheimer, & Knowlton, 2005;Gilboa et al, 2005; for theoretical analyses, see Moscovitch, Nadel, Winocur, Gilboa, & Rosenbaum, 2006;Shimamura, 2010).…”