A complementary systems account of word learning: neural and behavioural evidence

Abstract

In this paper we present a novel theory of the cognitive and neural processes by which adults learn new spoken words. This proposal builds on neurocomputational accounts of lexical processing and spoken word recognition and complementary learning systems (CLS) models of memory. We review evidence from behavioural studies of word learning that, consistent with the CLS account, show two stages of lexical acquisition: rapid initial familiarization followed by slow lexical consolidation. These stages map broadly onto two systems involved in different aspects of word learning: (i) rapid, initial acquisition supported by medial temporal and hippocampal learning, (ii) slower neocortical learning achieved by offline consolidation of previously acquired information. We review behavioural and neuroscientific evidence consistent with this account, including a meta-analysis of PET and functional Magnetic Resonance Imaging (fMRI) studies that contrast responses to spoken words and pseudowords. From this meta-analysis we derive predictions for the location and direction of cortical response changes following familiarization with pseudowords. This allows us to assess evidence for learning-induced changes that convert pseudoword responses into real word responses. Results provide unique support for the CLS account since hippocampal responses change during initial learning, whereas cortical responses to pseudowords only become word-like if overnight consolidation follows initial learning.

When words fail us: insights into language processing from developmental and acquired disorders

“…One, as discussed by Nation [25], is the growing literature exploring learning and lexical acquisition in adults (e.g. [55,56]). These experiments demonstrate the continuous and dynamic nature of learning and provide a potentially powerful methodology to consider individual differences in learning.…”

Bedding down new words: Sleep promotes the emergence of lexical competition in visual word recognition

“…This theory proposes a dual learning process whereby new information is initially encoded temporarily in the hippocampus, and then subsequently transitions to more stable, long-term representations in the neocortex. In particular, the word learning studies suggest a process of transition from hippocampal to neocortical lexical memory systems, facilitated by sleep (Davis & Gaskell, 2009). …”

The Impact of L2 Learning on Cognitive Aging

“…As discussed above, this result suggests bilingualism is associated with better maintenance of WM integrity in the course of cognitive aging [65]. However, Cummine and Boliek found greater integrity for adult monolinguals over bilinguals in the right inferior fronto-occipital fasciculus and the anterior thalamic radiation [66], which seems contradictory to Luck's findings (2011), but more consistent with those of Mohades et al (2012) in which no significant differences were observed between monolingual and bilingual children (aged 8 to 11) [67].…”

“…The hippocampus may be critically involved in the memory processes or vocabulary acquisition [77]. The learning of grammatical rules is linked to the frontal-striatal system, which connects frontal lobe regions with caudate nucleus and putamen [78].…”