Abstract
Speech production involves widely distributed brain regions. This MEG study focuses on the spectro-temporal dynamics that contribute to the setup of this network. In 21 participants performing a cue-target reading paradigm, we analyzed local oscillations during preparation for overt and covert reading in the time-frequency domain and localized sources using beamforming. Network dynamics were studied by comparing different dynamic causal models of beta phase coupling in and between hemispheres. While a broadband low frequency effect was found for any task preparation in bilateral prefrontal cortices, preparation for overt speech production was specifically associated with left-lateralized alpha and beta suppression in temporal cortices and beta suppression in motor-related brain regions. Beta phase coupling in the entire speech production network was modulated by anticipation of overt reading. We propose that the processes underlying the setup of the speech production network connect relevant brain regions by means of beta synchronization and prepare the network for left-lateralized information routing by suppression of inhibitory alpha and beta oscillations.
Highlights
Speech production is one of the most complex human motor acts as it bases upon linguistic processing but further requires precise sensorimotor integration
While a broadband low frequency effect was found for any task preparation in bilateral prefrontal cortices, preparation for overt speech production was associated with left-lateralized alpha and beta suppression in temporal cortices and beta suppression in motor-related brain regions
We propose that the processes underlying the setup of the speech production network connect relevant brain regions by means of beta synchronization and prepare the network for left-lateralized information routing by suppression of inhibitory alpha and beta oscillations
Summary
Speech production is one of the most complex human motor acts as it bases upon linguistic processing but further requires precise sensorimotor integration. Sensorimotor processing is more accessible than linguistic processing given the measurable physical auditory and motor signal properties. It is ideally suited to study spectro-temporal dynamics of large scale brain networks. As for other motor acts, motor preparation for speech production has been related to beta suppression in motor cortex (Salmelin et al, 2000; Saarinen et al, 2006). These processes could reflect covert feedforward processing prior to execution induced by a start signal and could serve as a model for the feedforward component of speech production
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