Correcting MEG artifacts caused by overt speech

Abstract

Recording brain activity during speech production using magnetoencephalography (MEG) can help us to understand the dynamics of speech production. However, these measurements are challenging due to the induced artifacts coming from several sources such as facial muscle activity, lower jaw and head movements. Here, we aimed to characterise speech-related artifacts and subsequently present an approach to remove these artifacts from MEG data. We recorded MEG from 11 healthy participants while they pronounced various syllables in different loudness. Head positions/orientations were extracted during speech production to investigate its role in MEG distortions. Finally, we present an artifact rejection approach using the combination of regression analysis and signal space projection (SSP) in order to correct the induced artifact from MEG data. Our results show that louder speech leads to stronger head movements and stronger MEG distortions. Our proposed artifact rejection approach could successfully remove the speech-related artifact and retrieve the underlying neurophysiological signals. As the presented artifact rejection approach was shown to remove artifacts induced by overt speech in the MEG, it will facilitate research addressing the neural basis of speech production with MEG.

The Role of Motor and Environmental Visual Rhythms in Structuring Auditory Cortical Excitability

“…As seen in the current and many previous studies, phase reset and entertainment of ongoing oscillations is most prevalent in extragranular layers (Lakatos et al, , 2007(Lakatos et al, , 2009O'Connell et al, 2011), and modulatory inputs targeting these layers have long thought to cause phase reset, and if stimuli are rhythmic, entrainment (Barczak et al, 2019;Lakatos et al, 2009;O'Connell et al, 2011O'Connell et al, , 2014. Besides anatomical studies, recent magnetoencephalographic studies investigating predictions in auditory scenes in humans found significant effective connectivity from motor cortex toward auditory areas (Abbasi and Gross, 2020;Morillon and Baillet, 2017). In addition, besides direct projections, an indirect source of motor influences on the auditory system could stem from the cochlea, as a recent study reported oscillations of the eardrum coinciding with saccade onset in the absence of sound (Gruters et al, 2018).…”

Oscillatory brain networks in continuous speaking and listening

“…b . Artefacts were removed from the recorded MEG data 41 . Individual MRIs were used to estimate source models per participant which were interpolated to a template volumetric grid.…”

“…Audio data was captured with a microphone, which was placed at a distance of 155 cm from the participants’ mouth, in order not to cause any artefacts through the microphone itself. Three pairs of EMG surface electrodes were placed after tactile inspection to find the correct location to capture muscle activity from the m. genioglossus, m. orbicularis oris, and m. zygomaticus major (for exact location see Figure 1 in Abbasi et al 41 ). One pair of electrodes was used for each muscle with about 1 cm between electrodes.…”

“…For removing the speech-related artefacts we used the pipeline presented in our recently published study 41 . In a nutshell, the artefact rejection comprises four major steps: (i) head movement-related artefact was initially reduced by incorporating the head position time-series into the general linear model (GLM) using regression analysis 85 .…”

“…Recently, we characterised the effects of head movement on the recorded MEG data during speech production 41 . In the same study, we also suggested an artefact rejection approach, based on regression analysis and signal space projection (SSP), to remove the induced head movement artefacts from the recorded MEG data and make the current study feasible.…”