Elsevier

NeuroImage

Volume 198, September 2019, Pages 283-295
NeuroImage

Frequency-specific brain dynamics related to prediction during language comprehension

https://doi.org/10.1016/j.neuroimage.2019.04.083Get rights and content
Under a Creative Commons license
open access

Highlights

  • MEG was recorded in naturalistic comprehension settings (auditory narratives).

  • We formalized prediction-related processing with word perplexity and word entropy.

  • We estimated MEG oscillatory power in theta, beta, alpha, and gamma bands.

  • Beta-band power was decreased for highly perplexing (unexpected) words.

  • Theta-band power was increased in high entropy (less predictable) contexts.

Abstract

The brain's remarkable capacity to process spoken language virtually in real time requires fast and efficient information processing machinery. In this study, we investigated how frequency-specific brain dynamics relate to models of probabilistic language prediction during auditory narrative comprehension. We recorded MEG activity while participants were listening to auditory stories in Dutch. Using trigram statistical language models, we estimated for every word in a story its conditional probability of occurrence. On the basis of word probabilities, we computed how unexpected the current word is given its context (word perplexity) and how (un)predictable the current linguistic context is (word entropy). We then evaluated whether source-reconstructed MEG oscillations at different frequency bands are modulated as a function of these language processing metrics. We show that theta-band source dynamics are increased in high relative to low entropy states, likely reflecting lexical computations. Beta-band dynamics are increased in situations of low word entropy and perplexity possibly reflecting maintenance of ongoing cognitive context. These findings lend support to the idea that the brain engages in the active generation and evaluation of predicted language based on the statistical properties of the input signal.

Keywords

MEG
Language model
Surprisal
Entropy
Neural oscillations

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