Presentations

Abstract

The representation of the novel word is thought to entail initial encoding in the contextual memory network (memory system
for episodes and events) and a subsequent shift to the semantic memory network (memory system for facts and knowledge).
According to the Complementary Learning System theory, this memory shift from context-based to a more lexicalised one
requires time. Behavioural works have shown that after integration, the processing of a novel word and its lexical neighbours
begin to influence each other. How is that reflected in the neural representation?
Several neuroimaging studies on novel word learning were conducted. In line with previous behavioural studies, the
lexical competition/facilitation effect emerged after a time of offline consolidation. Brain responses to novel words became
more similar to existing words also after a consolidation time. The use of two declarative memory systems, a contextual one
and a semantic one, depended on the time after learning but also on the type of information that was studied. Words with
referents or meanings were associated with more hippocampal involvement, an area which is thought to be the core structure
of episodic memory encoding and retrieval. Posterior middle temporal gyrus became more engaged when processing novel
words that had some time to consolidate. This area is known to function as a higher order association area, combining
multisensory information such as audio-visual integration, and as such it is an ideal structure to function as a lexical storage
area. We interpret the increase of this area to reflect lexicalisation of novel words.

Abstract

In line with two-stage models of memory, it has been proposed that memory traces for newly learned words are
initially dependent on medial temporal structures and acquire neocortical, more lexical representations during the first
night’s sleep after training (Davis & Gaskell, 2009). Only after sleep-dependent consolidation are novel words fully
integrated into the lexicon and are therefore able to enter into lexical competition with phonologically overlapping
existing words. This effect, observable as a slowing down of responses to existing words with a novel competitor, has
been demonstrated using various tasks including lexical decision, pause detection, semantic judgement, and wordspotting.