Oscillatory coupling in writing and writer's cramp

Area of Science:

• Neuroscience
• Movement Disorders
• Motor Control

Background:

• Writer's cramp is a focal task-induced dystonia impairing writing due to involuntary muscle contractions.
• The exact pathophysiological mechanisms of writer's cramp remain unclear.
• Understanding neural networks in writing is crucial for this movement disorder.

Purpose of the Study:

• To investigate the oscillatory neural network during physiological writing in healthy subjects.
• To unravel the oscillatory network underlying dystonic writing in writer's cramp patients.
• To compare cerebro-muscular and cerebro-cerebral coherence during writing between groups.

Main Methods:

• Whole-head magnetoencephalography (MEG) and dynamic imaging of coherent sources (DICS) were employed.
• Simultaneous surface electromyography (EMG) recorded muscle activity.
• Eleven healthy subjects and eight writer's cramp patients participated, writing for five minutes.

Main Results:

• Six brain areas showed consistent cerebro-muscular and cerebro-cerebral coherence in both groups: sensorimotor cortex, cerebellum, thalamus, premotor, and parietal cortex.
• Cerebro-muscular coherence occurred at writing frequencies (3-7 Hz); cerebro-cerebral coherence was observed around 10 Hz (8-13 Hz).
• Writer's cramp patients exhibited consistent coupling between both sensorimotor cortices, unlike controls.

Conclusions:

• The findings highlight distinct oscillatory network differences between healthy and writer's cramp subjects.
• Altered sensorimotor integration and bilateral pathophysiology are implicated in writer's cramp.
• This research provides insights into the neural basis of writer's cramp.