When listening to speech, brain responses time-lock to acoustic events in the stimulus. Recent studies have also reported that cortical responses track linguistic representations of speech. However, tracking of these representations is often described without controlling for acoustic properties. Therefore, the response to these linguistic representations might reflect unaccounted acoustic processing rather than language processing. Here we tested several recently proposed linguistic representations, using audiobook speech, while controlling for acoustic and other linguistic representations. Indeed, some of these linguistic representations were not significantly tracked after controlling for acoustic properties. However, phoneme surprisal, cohort entropy, word surprisal and word frequency were significantly tracked over and beyond acoustic properties. Additionally, these linguistic representations are tracked similarly across different stories, spoken by different readers. Together, this suggests that these representations characterize processing of the linguistic content of speech and might allow a behaviour-free evaluation of the speech intelligibility.
Neural markers of speech comprehension: measuring EEG tracking of linguistic speech representations, controlling the speech acoustics
