Abstract
Most studies exploring how remote memory is represented in the brain are based on strong episodic self-related components. Because of methodological reasons, much less is known about how the information concerning the semantic part of autobiographical memory is retrieved, and whether the brain correlates differ according to the autobiographical moment of the memory formation. In the present study, we explored the neural concomitants of the retrieval of texts learnt at different periods of life, in a comedian with exceptional verbal memory skills. This 49-year-old comedian was instructed to recite aloud a total of 30 texts he learnt during three different epochs: before the age of 15 years (E1), between the age of 15 and 25 years (E2), and after the age of 25 years (E3). The most salient activation was observed for memory from the farthest period, with a preponderance of the medial rostral prefrontal cortex (PFC) and of the precuneus. There was no hippocampal activation during text retrieval by comparison to a control condition, whatever the learning period. This study supports the assumption that the recall of remote semantic memories can occur without hippocampal activation. We discussed the activation of the rostral PFC during retrieval of the oldest (and best consolidated) memories as the possible involvement of control meta-memory processes rather than memory processes per se.
Highlights
Autobiographical memory, the recollection of episodes from an individual’s life, is composed of both episodic and semantic memories (Levine et al, 2002; Tulving, 2002)
There is a converging evidence that the hippocampus has a time-limited role in the acquisition and storage of semantic knowledge: the hippocampus appears to be essential for the formation and maintenance of semantic memory for a period of a few years after learning, while, as time passes, increasing involvement of multiple neocortical, especially frontal regions, was demonstrated (Smith & Squire, 2009)
We conducted a functional magnetic resonance imaging experiment to investigate the cerebral activation underlying the retrieval of semantic memories in this subject with exceptional verbal memory skills, comparing brain activation for texts learnt in three different periods of his lifetime
Summary
Autobiographical memory, the recollection of episodes from an individual’s life, is composed of both episodic (personal experiences that are specific in time and place) and semantic (general knowledge about the self-related world) memories (Levine et al, 2002; Tulving, 2002). While the recall of episodic memory along different periods of life has been extensively studied, this is much less true for semantic memory, and the process of consolidation of semantic memory into long-. We were able to overcome these difficulties by examining performance of a professional comedian who started to learn texts in the early childhood, and who is able to exactly settle texts acquisition in different periods of his life. This case represents a unique opportunity to better understand how semantic memories are represented in the brain according to the moment of acquisition in life. We conducted a functional magnetic resonance imaging (fMRI) experiment to investigate the cerebral activation underlying the retrieval of semantic memories in this subject with exceptional verbal memory skills, comparing brain activation for texts learnt in three different periods of his lifetime
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