title: Remote semantic memory is impoverished in hippocampal amnesia.
abstract: The necessity of the hippocampus for acquiring new semantic concepts is a topic of considerable debate. However, it is generally accepted that any role the hippocampus plays in semantic memory is time limited and that previously acquired information becomes independent of the hippocampus over time. This view, along with intact naming and word-definition matching performance in amnesia, has led to the notion that remote semantic memory is intact in patients with hippocampal amnesia. Motivated by perspectives of word learning as a protracted process where additional features and senses of a word are added over time, and by recent discoveries about the time course of hippocampal contributions to on-line relational processing, reconsolidation, and the flexible integration of information, we revisit the notion that remote semantic memory is intact in amnesia. Using measures of semantic richness and vocabulary depth from psycholinguistics and first and second language-learning studies, we examined how much information is associated with previously acquired, highly familiar words in a group of patients with bilateral hippocampal damage and amnesia. Relative to healthy demographically matched comparison participants and a group of brain-damaged comparison participants, the patients with hippocampal amnesia performed significantly worse on both productive and receptive measures of vocabulary depth and semantic richness. These findings suggest that remote semantic memory is impoverished in patients with hippocampal amnesia and that the hippocampus may play a role in the maintenance and updating of semantic memory beyond its initial acquisition.
authors.affiliation: Neuroscience Graduate Program, University of Iowa, United States.
authors.forename: Nathaniel B
authors.initials: NB
authors.lastname: Klooster
authors.affiliation: Neuroscience Graduate Program, University of Iowa, United States; Department of Communication Sciences and Disorders, University of Iowa, 250 Hawkins Drive, Iowa City, Iowa 52242, United States; Department of Neurology, University of Iowa, United States. Electronic address: melissa-duff@uiowa.edu.
authors.forename: Melissa C
authors.initials: MC
authors.lastname: Duff
mesh_terms: D000328:Adult; D000647:Amnesia / Q000473:pathology*; D000704:Analysis of Variance; D001245:Association Learning; D005260:Female; D006624:Hippocampus / Q000503:physiopathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D057567:Memory, Long-Term / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales; D011578:Psycholinguistics; D012660:Semantics; D014706:Verbal Learning / Q000502:physiology*; D014825:Vocabulary
keywords: Consolidation; Hippocampus; Remote memory; Semantic memory; Semantic richness