Speech Understanding Oppositely Affects Acoustic and Linguistic Neural Tracking in a Speech Rate Manipulation Paradigm
When listening to continuous speech, the human brain can track features of the presented speech signal. It has been shown that neural tracking of acoustic features is a prerequisite for speech understanding and can predict speech understanding in controlled circumstances. However, the brain also tra...
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Published in | The Journal of neuroscience Vol. 42; no. 39; pp. 7442 - 7453 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
United States
Society for Neuroscience
28.09.2022
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Subjects | |
Online Access | Get full text |
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Summary: | When listening to continuous speech, the human brain can track features of the presented speech signal. It has been shown that neural tracking of acoustic features is a prerequisite for speech understanding and can predict speech understanding in controlled circumstances. However, the brain also tracks linguistic features of speech, which may be more directly related to speech understanding. We investigated acoustic and linguistic speech processing as a function of varying speech understanding by manipulating the speech rate. In this paradigm, acoustic and linguistic speech processing is affected simultaneously but in opposite directions: When the speech rate increases, more acoustic information per second is present. In contrast, the tracking of linguistic information becomes more challenging when speech is less intelligible at higher speech rates. We measured the EEG of 18 participants (4 male) who listened to speech at various speech rates. As expected and confirmed by the behavioral results, speech understanding decreased with increasing speech rate. Accordingly, linguistic neural tracking decreased with increasing speech rate, but acoustic neural tracking increased. This indicates that neural tracking of linguistic representations can capture the gradual effect of decreasing speech understanding. In addition, increased acoustic neural tracking does not necessarily imply better speech understanding. This suggests that, although more challenging to measure because of the low signal-to-noise ratio, linguistic neural tracking may be a more direct predictor of speech understanding.
An increasingly popular method to investigate neural speech processing is to measure neural tracking. Although much research has been done on how the brain tracks acoustic speech features, linguistic speech features have received less attention. In this study, we disentangled acoustic and linguistic characteristics of neural speech tracking via manipulating the speech rate. A proper way of objectively measuring auditory and language processing paves the way toward clinical applications: An objective measure of speech understanding would allow for behavioral-free evaluation of speech understanding, which allows to evaluate hearing loss and adjust hearing aids based on brain responses. This objective measure would benefit populations from whom obtaining behavioral measures may be complex, such as young children or people with cognitive impairments. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 E.V. and M.G. contributed equally to this work as co-first authors. Author contributions: E.V., M.G., L.D., J.V., and T.F. designed research; E.V. and M.G. performed research; E.V., M.G., and L.D. analyzed data; E.V. wrote the first draft of the paper; E.V., M.G., L.D., J.V., and T.F. edited the paper; E.V. and M.G. wrote the paper. |
ISSN: | 0270-6474 1529-2401 |
DOI: | 10.1523/JNEUROSCI.0259-22.2022 |