The Cerebral Oscillatory Network of Writing – An MEG Study

Writing is a highly overlearned and complex movement. Functional MRI studies showed the involvement of both cortical and subcortical structures. A characterization of the dynamic interplay between the structures involved in writing is lacking up to now. We studied simultaneously brain activity with magnetoencephalography (MEG) and muscle activity with surface electromyography (EMG) during writing in 11 healthy subjects. Taking the muscle activity as reference we localized brain regions involved in the writing task by using the analysis tool Dynamic Imaging of Coherent Sources (DICS) and characterized the dynamic interplay of these sources. Analysis revealed that writing involves a spatially distributed oscillatory network including the bilateral primary sensorimotor cortex, the ipsilateral cerebellum, the contralateral premotor and posterior parietal cortex and the contralateral thalamus. These cerebral sources are coherent with the muscles primarily at writing frequency (3–7Hz), whereas the cerebral sources mainly show coherence at around 7–13Hz. Our results show that writing is based on an extensive motor network. The involved brain regions are coherent at around 10Hz. Therefore, our study supports the notion of a common motor frequency around 10Hz.