Effects of novel word consolidation on evoked and induced EEG activity

Bakker, I. 1, 2 , Takashima, A. . 1, 2 , Janzen, G. 1, 2 , Van Hell, J. 3, 1 & McQueen, J. M. 1, 2, 4

1 Behavioural Science Institute, Radboud University Nijmegen, The Netherlands
2 Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, The Netherlands
3 Pennsylvania State University
4 Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands

Integration of novel words into the mental lexicon (lexicalisation) has been hypothesised to benefit from offline consolidation. In the current study, we examined the effect of novel word consolidation on induced and evoked components of the EEG signal. On two consecutive days, participants memorised two sets of 30 novel and 30 existing words with definitions. Subsequently, we measured EEG responses to novel and existing words learned on day 1 (remote) or day 2 (recent), and to untrained words. Analysis of oscillatory activity revealed that differences between novel and existing words in the theta band decreased gradually with training and consolidation. The lower beta band showed a selective response to lexicalised words, whereas upper beta appeared to be more sensitive to (episodic) memory accessibility. In a second task, novel words were primed by either a semantically related or unrelated existing word. A consolidation effect was observed in the difference in N400 amplitude to novel versus existing words. However, an N400 reduction after related primes was found in all conditions, suggesting that the semantic N400 effect is not sensitive to lexicalisation. These data support the hypothesis that offline consolidation aids lexicalisation, but suggest that not all word-like behaviour requires lexicalised memory traces.