Huizeling, E. | bioRxiv Science

bioRxiv2022

The Interaction of Context Constraints and Predictive Validity during Sentence Reading

Words are not processed in isolation, instead they are commonly embedded in phrases and sentences. The sentential context influences the perception and processing of a word. However, how this is achieved by brain processes and whether predictive mechanisms underlie this process remains a debated topic. To this end we employed an experimental paradigm in which we orthogonalized sentence context constraints and predictive validity, which was defined as the ratio of congruent to incongruent sentence endings within the experiment. While recording electroencephalography, participants read sentences with three levels of sentential context constraints (high, medium and low). Participants were also separated into two groups, which differed in their ratio of valid congruent to incongruent target words that could be predicted from the sentential context. For both groups we investigated modulations of alpha power before, and N400 amplitude modulations after target word onset. The results reveal that the N400 amplitude gradually decreases with higher context constraints. Contrary, alpha power is non-monotonically influenced, displaying the strongest decrease for high context constraints over frontal electrode sites, while alpha power between medium and low context constraints does not differ. This indicates that both neural correlates are influenced by the degree of context constraint but are not affected by changes in predictive validity. The results therefore suggest that both N400 and alpha power are not unequivocally linked to the predictability of a target word based on larger contextual information.

neuroscience↗

bioRxiv2020

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

Typical adults read remarkably quickly. Such 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 intact and scrambled sentences. 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 confirms that frequency influences word processing independently of predictability, and that contextual constraints affect word-by-word brain responses. With a conservative multiple comparisons correction, only the interaction between lexical frequency and surprisal survived, in anterior temporal and frontal cortex, and not between lexical frequency and entropy, nor between lexical frequency and index. However, interestingly, the uncorrected index*frequency interaction revealed an effect in left frontal and temporal cortex that reversed in time and space for intact compared to scrambled sentences. Finally, we provide evidence to suggest that, in sentences, lexical frequency and predictability may independently influence early (<150ms) and late stages of word processing, but also interact during late stages of word processing (>150-250ms), thus helping to converge previous contradictory eye-tracking and electrophysiological literature. Current neuro-cognitive models of reading would benefit from accounting for these differing effects of lexical frequency and predictability on different stages of word processing.

neuroscience↗