Cortical activity during speech and non-speech oromotor tasks: A magnetoencephalography (MEG) study

We used whole-head magnetoencephalography to investigate cortical activity during two oromotor activities foundational to speech production. 13 adults performed mouth opening and phoneme (/pa/) production tasks to a visual cue. Jaw movements were tracked with an ultrasound-emitting device. Trials were time-locked to both stimulus onset and peak of jaw displacement. An event-related beamformer source reconstruction algorithm was used to detect areas of cortical activity for each condition. Beamformer output was submitted to iterative K-means clustering analyses. The time course of neural activity at each cluster centroid was computed for each individual and condition. Peaks were identified and latencies submitted for statistical analysis to reveal the relative timing of activity in each brain region. Stimulus locked activations for the mouth open task included a progression from left cuneus to left frontal and then right pre-central gyrus. Phoneme generation revealed the same sequence but with bilateral frontal activation. When time locked to jaw displacement, the mouth open condition showed left frontal followed by right frontal–temporal areas. Phoneme generation showed a complicated sequence of bilateral temporal and frontal areas. This study used three unique approaches (beamforming, clustering and jaw tracking) to demonstrate the temporal progression of neural activations that underlie the motor control of two simple oromotor tasks. These findings have implications for understanding clinical conditions with deficits in articulatory control or motor speech planning.

► Timing of cortical activations during 2 oromotor speech-related tasks was examined.
► Event-related beamformer source reconstruction and iterative clustering used.
► Ultrasound emitting jaw tracking device used to time-lock to jaw displacement.
► Individual time courses were peak picked to see temporal progression of activations.
► Study has implications for conditions with articulatory or motor planning deficits.