The spatiotemporal dynamics of bottom-up and top-down processing during at-a-glance reading

Like all domains of cognition, language processing is affected by top-down knowledge. Classic evidence for this is missing blatant errors in the signal. In sentence comprehension, one instance of this is failing to notice word order errors, such as transposed words in the middle of a sentence: you that read wrong (Mirault et al., 2018). Our brains seem to fix such errors, since they are incompatible with our grammatical knowledge. But how do our brains do this? Following behavioral work on inner transpositions, we flashed four-word sentences for 300ms using rapid parallel visual presentation (RPVP, Snell and Grainger, 2017). We compared their magnetoencephalography responses to fully grammatical and reversed sentences. Left lateral language cortex robustly distinguished grammatical and reversed sentences starting at 213ms. Thus, the influence of grammatical knowledge begun rapidly after visual word form recognition (Tarkiainen et al., 1999). At the earliest stage of this neural "sentence superiority effect," inner transpositions patterned between grammatical and reversed sentences, showing evidence that the brain initially "noticed" the error. However, a hundred millisecond later, the inner transpositions became indistinguishable from the grammatical sentences, suggesting that at this point, the brain had "fixed" the error. These results show that after a single glance at a sentence, syntax impacts our neural activity almost as quickly as higher-level object recognition is assumed to take place (Cichy et al., 2014). The earliest stage involves a detailed comparison between the bottom-up input and grammatical knowledge, while shortly afterwards, knowledge can override an error in the stimulus.