Left-lateralization of speech production is indexed by the amplitude of preparatory alpha desynchronization

Large scale brain networks are ideal to study communication between brain regions. Given that the speech production network consists of various control, motor and sensory regions we hypothesized that different brain rhythms contribute to the intention to speak. By using a cue-target paradigm during MEG, allowing us to separate cognitive preparation from motor preparation, we investigated how the speech production network is prepared and set up. When intending to read aloud, delta power increases in the bilateral mesial alertness system. A decrease in alpha and low-beta is observed in regions performing sensorimotor integration. High-beta power decreases in feedforward articulatory motor areas. This indicates that the status quo of the motor system is already altered by cognitive processes prior to motor preparation. A task dependent decrease in alpha power is primarily found in visual and auditory cortices. A decrease in inhibitory alpha could engage these brain regions in the reading / speech production network. Interestingly, alpha decrease is lateralised to the left in secondary auditory cortices. This supports the notion that properties of secondary auditory cortices contribute substantially to left-lateralisation of speech production*.

Literatur: * Kell et al. (2011) Cereb Cortex, 21:932-937