title: Richness of information about novel words influences how episodic and semantic memory networks interact during lexicalization.
abstract: The complementary learning systems account of declarative memory suggests two distinct memory networks, a fast-mapping, episodic system involving the hippocampus, and a slower semantic memory system distributed across the neocortex in which new information is gradually integrated with existing representations. In this study, we investigated the extent to which these two networks are involved in the integration of novel words into the lexicon after extensive learning, and how the involvement of these networks changes after 24h. In particular, we explored whether having richer information at encoding influences the lexicalization trajectory. We trained participants with two sets of novel words, one where exposure was only to the words' phonological forms (the form-only condition), and one where pictures of unfamiliar objects were associated with the words' phonological forms (the picture-associated condition). A behavioral measure of lexical competition (indexing lexicalization) indicated stronger competition effects for the form-only words. Imaging (fMRI) results revealed greater involvement of phonological lexical processing areas immediately after training in the form-only condition, suggesting that tight connections were formed between novel words and existing lexical entries already at encoding. Retrieval of picture-associated novel words involved the episodic/hippocampal memory system more extensively. Although lexicalization was weaker in the picture-associated condition, overall memory strength was greater when tested after a 24hour delay, probably due to the availability of both episodic and lexical memory networks to aid retrieval. It appears that, during lexicalization of a novel word, the relative involvement of different memory networks differs according to the richness of the information about that word available at encoding.
authors: Radboud University Nijmegen, Behavioural Science Institute, P.O. Box 9104, 6500 HE Nijmegen, The Netherlands; Radboud University Nijmegen, Donders Institute for Brain, Cognition and Behaviour, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands. Electronic address: Atsuko.Takashima@fcdonders.ru.nl.
authors: Atsuko
authors: A
authors: Takashima
authors: Iske
authors: I
authors: Bakker
authors: Janet G
authors: JG
authors: van Hell
authors: Gabriele
authors: G
authors: Janzen
authors: James M
authors: JM
authors: McQueen
mesh_terms: D000293:Adolescent; D000328:Adult; D001245:Association Learning / Q000502:physiology*; D001931:Brain Mapping; D005260:Female; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D008297:Male; D061212:Memory, Episodic; D019579:Neocortex / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D012660:Semantics; D014706:Verbal Learning / Q000502:physiology*; D055815:Young Adult
keywords: Associative memory; Complementary learning systems; FWE; GLM; HRF; Hemodynamic Response Function; IFG; Lexical acquisition; MTG; MTL; Overnight consolidation; PPI; ROI; RT; STG; SVC; fMRI; family-wise error corrected; functional magnetic resonance imaging; general linear model; inferior frontal gyrus; medial temporal lobe; middle temporal gyrus; psycho-physiological interaction; reaction time; region of interest; small volume correction; superior temporal gyrus