title: Removing speech artifacts from electroencephalographic recordings during overt picture naming.
abstract: A number of electroencephalography (EEG) studies have investigated the time course of brain activation during overt word production. The interpretation of their results is complicated by the fact that articulatory movements may mask the cognitive components of interest. The first aim of the present study was to investigate when speech artifacts occur during word production planning and what effects they have on the spatio-temporal neural activation pattern. The second aim was to propose a new method that strongly attenuates speech artifacts during overt picture naming and to compare it with existing methods. EEG and surface electromyograms (EMGs) of the lips were recorded while participants overtly named pictures in a picture-word interference paradigm. The comparison of the raw data with lip EMG and the comparison of source localizations of raw and corrected EEG data showed that speech artifacts occurred mainly from ~400 ms post-stimulus onset, but some earlier artifacts mean that they occur much earlier than hitherto assumed. We compared previously used methods of speech artifacts removal (SAR) with a new method, which is based on Independent Component Analysis (SAR-ICA). Our new method clearly outperformed other methods. In contrast to other methods, there was only a weak correlation between the lip EMG and the corrected data by SAR-ICA. Also, only the data corrected with our method showed activation of cerebral sources consistent with meta-analyses of word production.
authors.affiliation: LET'S-ISTC-CNR, Ospedale Fatebenefratelli, Isola Tiberina, Rome, Italy; Institute of Neuroscience, Newcastle University, UK; Neural Control of Movement Lab, Department of Health Sciences and Technology ETH Zurich, Switzerland. Electronic address: camillo.porcaro@istc.cnr.it.
authors.forename: Camillo
authors.initials: C
authors.lastname: Porcaro
authors.affiliation: LET'S-ISTC-CNR, Ospedale Fatebenefratelli, Isola Tiberina, Rome, Italy; School of Psychology and BUIC, University of Birmingham, UK.
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Medaglia
authors.affiliation: School of Psychology and BUIC, University of Birmingham, UK.
authors.forename: Andrea
authors.initials: A
authors.lastname: Krott
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000502:physiology*; D004569:Electroencephalography / Q000379:methods*; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D012815:Signal Processing, Computer-Assisted; D013060:Speech / Q000502:physiology*; D055815:Young Adult
keywords: Electroencephalography (EEG); Independent Component Analysis (ICA); Overt speech production; Speech artifacts