Hippocampal Activation for Autobiographical Memories over the Entire Lifetime in Healthy Aged Subjects: An fMRI Study

Abstract

We used functional magnetic resonance imaging to determine the cerebral structures required during the recollection of episodic autobiographical memories according to 5 time periods covering the whole lifespan to test the 2 concurring models of memory consolidation, which propose either a temporary (standard model) or a permanent (multiple-trace model) role of the hippocampus in episodic memory retrieval. The experimental paradigm was specially designed to engage subjects (67.17 +/- 5.22 years old) in the retrieval of episodic autobiographical memories, whatever the time period, from personally relevant cues selected by questioning a family member. Moreover, the nature of the memories was checked at debriefing by means of behavioral measures to control the degree of episodicity. Behavioral data showed that recollected memories were characterized by specificity and details whatever their remoteness. Main neuroimaging data (Statistical Parametric Mapping 99) revealed the activation of a network including the left superior frontal gyri, bilateral precuneus/posterior cingulate and lingual gyri, left angular gyrus, and left hippocampus, although the subtraction analyses detected subtle differences between certain time periods. Small volume correction centered on the hippocampus detected left hippocampal activation for all time periods and additional right hippocampal activation for the intermediate periods. Further confirmation was provided by using a 3-way analysis of variance on blood oxygen level-dependent values, which revealed hippocampal activation whatever the time interval. The present data challenge the standard model of memory consolidation and support the multiple-trace model, instead. The comparison with previous literature stresses the idea that a bilateral involvement of the hippocampus characterizes rich episodic autobiographical memory recollection.

Functional neuroimaging of autobiographical memory

“…SCM predicts greater hippocampal activity for recent than remote AMs (i.e., a remoteness effect), whereas MTT predicts that if both types of AMs are equally detailed and vivid, they should elicit similar hippocampal activity (i.e., no remoteness effect). Although a few functional neuroimaging studies found the remoteness effect predicted by SCM (Niki & Luo, 2002;Piefke, et al, 2003) most of the studies comparing remote and recent AMs did not, supporting MTT Conway, et al, 1999;Gilboa, et al, 2004;Maguire & Frith, 2003b;Maguire, et al, 2001;Piolino et al, 2004;Rekkas & Constable, 2005;Ryan, et al, 2001;Viard et al, 2007) and consistent with emerging evidence in the patient literature, which suggests that MTL damage can impact remote AMs greater than was previously found (Steinvorth, et al, 2005). However, neuroimaging evidence cannot irrefutably determine the necessity of the hippocampus in the retrieval of remote AMs.…”

“…Also, there is evidence of hemispheric asymmetries in the remoteness effect (Maguire & Frith, 2003b;Viard, et al, 2007), and aging is known to reduce hemispheric asymmetries in brain activity (Cabeza, 2002). In fact, fMRI studies have found activity in the left hippocampus in young adults, whereas, bilateral activity has been found in older adults for some remote periods (Maguire & Frith, 2003a;Viard, et al, 2007), but the effects of remoteness and age have not been disentangled.…”

Subjective vs. documented reality: A case study of long-term real-life autobiographical memory

“…Some authors consider the hippocampus essential for consolidation and for retrieval of recent but not remote declarative memories (Squire Kirwan et al 2008). Others propose that the hippocampus remains vital in recollection (Nadel and Moscovitch 1997;Rosenbaum et al 2008), provided the remote memories are reexperienced vividly Viard et al 2007;Piolino et al 2008). Since AM recollection tends to lose its vividness over time Piolino et al 2008), we contend that the attenuation in hippocampal activity might be attributed to reduced vividness in recollection.…”

“…These regions were selected based on their reported involvement in consolidation and retrieval of episodic memories Cabeza and Jacques 2007;Viard et al 2007). Data from the VQ test at both Recent and Remote interval scans were extracted for the above ROIs, using GLM 1 (''general'' model) and GLM 3 (''confidence'' model).…”

Bewusstsein und Gedächtnis: Die Bedeutung der Kohärenz und Konsistenz von Erinnerungen

“…Andere Bildgebungsstudien berichten flache oder keine Zeitgradienten der Hippocampusaktivität im Zusammenhang mit dem Abruf autobiographischer Episoden und unterstützten insofern eher die MTT (z.^B. Ryan et al 2001;Viard et al 2007;Cabeza und St. Jacques 2007). Abbildung 4 zeigt die differentiellen Aktivierungen des Hippocampus während des Abrufs rezenter emotionaler autobiographischer Episoden (relativ zu emotionalen Erinnerungen an Kindheitsepisoden), die Piefke et al (2003) berichteten.…”