Essential tremor disrupts rhythmic brain networks during naturalistic movement

Area of Science:

• Neuroscience
• Neurology
• Biophysics

Background:

• Essential Tremor (ET) is a common neurological disorder causing involuntary rhythmic movements due to abnormal brain circuit synchronization.
• Previous research often studied tremor in isolation, neglecting its impact on naturalistic motor control during tasks like reaching.

Purpose of the Study:

• To investigate how ET disrupts the sequential engagement of large-scale brain networks during upper-limb reaching.
• To determine if ET-related network disturbances contribute to both tremor and motor planning/execution deficits.

Main Methods:

• Used high-density electroencephalography (EEG) and optically pumped magnetoencephalography (MEG) in ET patients and healthy controls during a reaching task.
• Applied a novel dimensionality reduction technique to analyze brain-wide oscillations and network engagement.
• Correlated neuroimaging findings with tremor severity and movement kinematics.

Main Results:

• Key motor regions showed synchronization with tremor rhythms in ET patients.
• ET patients exhibited increased low beta desynchronization in the supplementary motor area, correlating strongly with tremor severity (R² = 0.85).
• A novel analysis revealed four distinct motor networks, with ET altering their sequential engagement, particularly affecting the frontoparietal beta network crucial for motor planning.

Conclusions:

• ET fundamentally disrupts distributed motor control networks, affecting both tremor generation and motor planning/execution.
• Altered network engagement in ET patients correlates with slower movements, suggesting a shift towards feedback-dependent motor control.
• Identified novel biomarkers in brain oscillations and network dynamics for ET, offering targets for advanced brain stimulation therapies.