Speech perception, production, and the sensorimotor mu rhythm

The EEG mu (μ) rhythm is considered a measure of sensorimotor integration. This rhythm is commonly identified by co-occuring peaks at ~10´Hz(alpha) and ~20 Hz (beta) across the sensorimotor cortex. Suppression of the power within peaks are thought to reflect somatosensory and motor aspects of processing respectively. Suppression of μ power (especially in the beta peak) has been found when performing, imagining or perceiving relevant action (e.g., while watching hand movements and oro-facial movements). μ suppression has also been found to visual speech perception, listening to speech in noise, and when mentally segmenting speech for auditory discrimination, suggesting that it is a sensitive measure of audio-motor integration in speech. The two main goals in this study are to bolster understanding of the timing and function of dorsal stream activity in speech perception by examining ERS/ERD patterns in quiet and noisy discrimination conditions and to provide initial evidence that, via the application of ICA / ERSP, the use of EEG can be extended effectively into speech production. 17 of 20 participants provided left and right p components that were common to perception and production tasks. The most probably source of these components was the premotor cortex (BA 6) with primary motor cortex (BA 4) and primary somatosensory (BA 2/3) cortex providing additional possible sources. Fewer (8 and 7 of 20) participants provided components with average equivalent dipoles emanating from BA 22 and BA 7, respectively, with alpha activity suggesting entrainment within the dorsal stream.