Articulation Artifacts During Overt Language Production in Event-Related Brain Potentials: Description and Correction

Abstract

Overt articulation produces strong artifacts in the electroencephalogram and in event-related potentials (ERPs), posing a serious problem for investigating language production with these variables. Here we describe the properties of articulation-related artifacts and propose a novel correction procedure. Experiment 1 co-recorded ERPs and trajectories of the articulators with an electromagnetic articulograph from a single participant. The generalization of the findings from the single participant to standard picture naming was investigated in Experiment 2. Both experiments provided evidence that articulation-induced artifacts may start up to 300 ms or more prior to voice onset or voice key onset-depending on the specific measure; they are highly similar in topography across many different phoneme patterns and differ mainly in their time course and amplitude. ERPs were separated from articulation-related artifacts with residue iteration decomposition (RIDE). After obtaining the artifact-free ERPs, their correlations with the articulatory trajectories dropped near to zero. Artifact removal with independent component analysis was less successful; while correlations with the articulatory movements remained substantial, early components prior to voice onset were attenuated in reconstructed ERPs. These findings offer new insights into the nature of articulation artifacts; together with RIDE as method for artifact removal the present report offers a fresh perspective for ERP studies requiring overt articulation.

Word onset phonetic properties and motor artifacts in speech production EEG recordings

“…Note that the increases in gamma and beta band power were detected earliest around 150 ms before vocal onset for the voiceless phoneme /p/ and around 100 ms for the voiced phoneme /b/. These observations are at variance with previous studies, which found different (i.e., earlier) time distribution of the artifact (see Ouyang et al, 2016;Porcaro et al, 2015). Such differences could be largely due to methodological decisions (see van der Linden et al, 2014).…”

“…Muscular activity incidental to speech production (such as prephonatory breath) is also associated with cortical potentials recorded by EEG and MEG that might be indiscernible from the cortical activity generated by the cognitive processes of interest (Deecke, Engel, Lang, & Kornhuber, 1986;Tremoureux et al, 2014;Yoshida et al, 1999). In addition, research using vocal response paradigms faces the problem of concomitant muscular activity (e.g., face muscles for jaw movements, glossokinetic artifacts from tongue movements) during speech production or in the period preceding articulation (e.g., De Vos et al, 2010;Ganushchak & Schiller, 2008;Goncharova, McFarland, Vaughan, & Wolpaw, 2003;Ouyang et al, 2016;Porcaro, Medaglia, & Krott, 2015;van der Linden et al, 2014;Whitham et al, 2007). This EMG activity is known to contaminate the EEG signal of interest.…”

The Effect of Lexical Cohort Size Is Independent of Semantic Context Effects in a Picture–Word Interference Task: A Combined ERP and sLORETA Study

“…Studies regarding speech production have shown that stimulusaligned Event-Related Potentials (ERPs) could be well employed without significant contamination to the signals before articulation (Dell'Acqua et al, 2010;Aristei et al, 2011;Janssen et al, 2015;Rose and Abdel Rahman, 2017). Since articulation-related artifacts may emerge around 150 ms (Fargier et al, 2017) or 300 ms before voice onset (Ouyang et al, 2016), it is effective to analyze the semantic context effects occurring in the stage of word planning rather than articulatory buffering (Roelofs and Piai, 2015).…”

Variation in the speech signal as a window into the cognitive architecture of language production

“…Note, however, that studies in which the EEG is recorded while the participants perform an overt production task have usually avoided exploiting the signal during the articulation or shortly before. The electromyographic activity resulting from movement of the articulators contaminates the EEG signal during and before the articulation (e.g., De Vos et al, 2010;Ganushchak & Schiller, 2008;Goncharova, McFarland, Vaughan, & Wolpaw, 2003;Ouyang et al, 2016;Porcaro, Medaglia, & Krott, 2015). How long before the articulation the signal is contaminated is a matter of discussion (e.g., Fargier, Bürki, Pinet, Alario, & Laganaro, 2017;Ouyang et al, 2016;Porcaro et al, 2015), but several studies have suggested that the phonological encoding process and at least part of the phonetic encoding processes can be investigated with EEG (see Bürki, Pellet-Cheneval, & Laganaro, 2015, or Laganaro, Python, & Toepel, 2013.…”

“…The electromyographic activity resulting from movement of the articulators contaminates the EEG signal during and before the articulation (e.g., De Vos et al, 2010;Ganushchak & Schiller, 2008;Goncharova, McFarland, Vaughan, & Wolpaw, 2003;Ouyang et al, 2016;Porcaro, Medaglia, & Krott, 2015). How long before the articulation the signal is contaminated is a matter of discussion (e.g., Fargier, Bürki, Pinet, Alario, & Laganaro, 2017;Ouyang et al, 2016;Porcaro et al, 2015), but several studies have suggested that the phonological encoding process and at least part of the phonetic encoding processes can be investigated with EEG (see Bürki, Pellet-Cheneval, & Laganaro, 2015, or Laganaro, Python, & Toepel, 2013. Important efforts have also been put into developing and testing ways of removing artifacts from the EEG signal of interest (James & Hesse, 2005;Ouyang et al, 2016;Pham, Fine, & Semrud-Clikeman, 2011;Urigüen & Garcia-Zapirain, 2015;Vigario & Oja, 2008).…”