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Effect of number and placement of EEG electrodes on measurement of neural tracking of speech

Measurement of neural tracking of natural running speech from the electroencephalogram (EEG) is an increasingly popular method in auditory neuroscience and has applications in audiology. The method involves decoding the envelope of the speech signal from the EEG signal, and calculating the correlati...

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Autores principales: Montoya-Martínez, Jair, Vanthornhout, Jonas, Bertrand, Alexander, Francart, Tom
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7877609/
https://www.ncbi.nlm.nih.gov/pubmed/33571299
http://dx.doi.org/10.1371/journal.pone.0246769
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author Montoya-Martínez, Jair
Vanthornhout, Jonas
Bertrand, Alexander
Francart, Tom
author_facet Montoya-Martínez, Jair
Vanthornhout, Jonas
Bertrand, Alexander
Francart, Tom
author_sort Montoya-Martínez, Jair
collection PubMed
description Measurement of neural tracking of natural running speech from the electroencephalogram (EEG) is an increasingly popular method in auditory neuroscience and has applications in audiology. The method involves decoding the envelope of the speech signal from the EEG signal, and calculating the correlation with the envelope of the audio stream that was presented to the subject. Typically EEG systems with 64 or more electrodes are used. However, in practical applications, set-ups with fewer electrodes are required. Here, we determine the optimal number of electrodes, and the best position to place a limited number of electrodes on the scalp. We propose a channel selection strategy based on an utility metric, which allows a quick quantitative assessment of the influence of a channel (or a group of channels) on the reconstruction error. We consider two use cases: a subject-specific case, where the optimal number and position of the electrodes is determined for each subject individually, and a subject-independent case, where the electrodes are placed at the same positions (in the 10-20 system) for all the subjects. We evaluated our approach using 64-channel EEG data from 90 subjects. In the subject-specific case we found that the correlation between actual and reconstructed envelope first increased with decreasing number of electrodes, with an optimum at around 20 electrodes, yielding 29% higher correlations using the optimal number of electrodes compared to all electrodes. This means that our strategy of removing electrodes can be used to improve the correlation metric in high-density EEG recordings. In the subject-independent case, we obtained a stable decoding performance when decreasing from 64 to 22 channels. When the number of channels was further decreased, the correlation decreased. For a maximal decrease in correlation of 10%, 32 well-placed electrodes were sufficient in 91% of the subjects.
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spelling pubmed-78776092021-02-19 Effect of number and placement of EEG electrodes on measurement of neural tracking of speech Montoya-Martínez, Jair Vanthornhout, Jonas Bertrand, Alexander Francart, Tom PLoS One Research Article Measurement of neural tracking of natural running speech from the electroencephalogram (EEG) is an increasingly popular method in auditory neuroscience and has applications in audiology. The method involves decoding the envelope of the speech signal from the EEG signal, and calculating the correlation with the envelope of the audio stream that was presented to the subject. Typically EEG systems with 64 or more electrodes are used. However, in practical applications, set-ups with fewer electrodes are required. Here, we determine the optimal number of electrodes, and the best position to place a limited number of electrodes on the scalp. We propose a channel selection strategy based on an utility metric, which allows a quick quantitative assessment of the influence of a channel (or a group of channels) on the reconstruction error. We consider two use cases: a subject-specific case, where the optimal number and position of the electrodes is determined for each subject individually, and a subject-independent case, where the electrodes are placed at the same positions (in the 10-20 system) for all the subjects. We evaluated our approach using 64-channel EEG data from 90 subjects. In the subject-specific case we found that the correlation between actual and reconstructed envelope first increased with decreasing number of electrodes, with an optimum at around 20 electrodes, yielding 29% higher correlations using the optimal number of electrodes compared to all electrodes. This means that our strategy of removing electrodes can be used to improve the correlation metric in high-density EEG recordings. In the subject-independent case, we obtained a stable decoding performance when decreasing from 64 to 22 channels. When the number of channels was further decreased, the correlation decreased. For a maximal decrease in correlation of 10%, 32 well-placed electrodes were sufficient in 91% of the subjects. Public Library of Science 2021-02-11 /pmc/articles/PMC7877609/ /pubmed/33571299 http://dx.doi.org/10.1371/journal.pone.0246769 Text en © 2021 Montoya-Martínez et al http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
spellingShingle Research Article
Montoya-Martínez, Jair
Vanthornhout, Jonas
Bertrand, Alexander
Francart, Tom
Effect of number and placement of EEG electrodes on measurement of neural tracking of speech
title Effect of number and placement of EEG electrodes on measurement of neural tracking of speech
title_full Effect of number and placement of EEG electrodes on measurement of neural tracking of speech
title_fullStr Effect of number and placement of EEG electrodes on measurement of neural tracking of speech
title_full_unstemmed Effect of number and placement of EEG electrodes on measurement of neural tracking of speech
title_short Effect of number and placement of EEG electrodes on measurement of neural tracking of speech
title_sort effect of number and placement of eeg electrodes on measurement of neural tracking of speech
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7877609/
https://www.ncbi.nlm.nih.gov/pubmed/33571299
http://dx.doi.org/10.1371/journal.pone.0246769
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