Lexical frequency and sentence context influence the brain’s response to single words

Abstract

Remarkably fast reading is facilitated by brain processes that are sensitive to both word frequency and contextual constraints. It is debated as to whether these attributes have additive or interactive effects on language processing in the brain. We investigated this issue by analysing existing magnetoencephalography data from 99 participants reading sentences and word-lists. Using a cross-validated model comparison scheme, we found that lexical frequency predicted the word-by-word elicited MEG signal in a widespread cortical network, irrespective of sentential context. In contrast, index (ordinal word position) was more strongly encoded in sentence words, in left front-temporal areas. This suggests that frequency influences word processing independently of predictability, and that contextual constraints affect word-by-word brain responses. Interestingly, an exploration of the index*frequency interaction revealed an effect (in left frontal and temporal cortex) that reversed in time and space for sentences compared to word-lists. These findings may improve future neuro-cognitive models of reading.