More than words: Neurophysiological correlates of semantic dissimilarity depend on comprehension of the speech narrative. Eur J Neurosci 2022 Oct;56(8):5201-5214
Date
08/23/2022Pubmed ID
35993240DOI
10.1111/ejn.15805Scopus ID
2-s2.0-85137990883 (requires institutional sign-in at Scopus site) 18 CitationsAbstract
Speech comprehension relies on the ability to understand words within a coherent context. Recent studies have attempted to obtain electrophysiological indices of this process by modelling how brain activity is affected by a word's semantic dissimilarity to preceding words. Although the resulting indices appear robust and are strongly modulated by attention, it remains possible that, rather than capturing the contextual understanding of words, they may actually reflect word-to-word changes in semantic content without the need for a narrative-level understanding on the part of the listener. To test this, we recorded electroencephalography from subjects who listened to speech presented in either its original, narrative form, or after scrambling the word order by varying amounts. This manipulation affected the ability of subjects to comprehend the speech narrative but not the ability to recognise individual words. Neural indices of semantic understanding and low-level acoustic processing were derived for each scrambling condition using the temporal response function. Signatures of semantic processing were observed when speech was unscrambled or minimally scrambled and subjects understood the speech. The same markers were absent for higher scrambling levels as speech comprehension dropped. In contrast, word recognition remained high and neural measures related to envelope tracking did not vary significantly across scrambling conditions. This supports the previous claim that electrophysiological indices based on the semantic dissimilarity of words to their context reflect a listener's understanding of those words relative to that context. It also highlights the relative insensitivity of neural measures of low-level speech processing to speech comprehension.
Author List
Broderick MP, Zuk NJ, Anderson AJ, Lalor ECAuthor
Andrew J. Anderson PhD Assistant Professor in the Neurology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Auditory PerceptionComprehension
Electroencephalography
Humans
Semantics
Speech
Speech Perception
