Cortical dynamics within and between parietal and motor cortex in essential tremor.

Area of Science:

• Neuroscience
• Movement Disorders
• Systems Neuroscience

Background:

• Functional imaging suggests parietal and motor cortex activity correlates with essential tremor severity under increased visual feedback.
• Previous research implicates the cerebellar-thalamo-cortical motor circuit in essential tremor.

Purpose of the Study:

• To investigate the association between cortical oscillations and connectivity in parietal and motor cortices with worsening essential tremor under high visual feedback.
• To determine how essential tremor patients' cortical activity and connectivity differ from controls in response to visual feedback.

Main Methods:

• High-density electroencephalogram (EEG) and source localization were used to measure cortical activity in 24 essential tremor patients and 17 controls.
• Cortical activity and tremor magnitude were assessed under both low and high visual feedback conditions.
• Analysis focused on power changes in the 4-12 Hz and 12-30 Hz bands and bidirectional connectivity between parietal and motor cortices.

Main Results:

• Essential tremor patients exhibited reduced power in the 4-12 Hz and 12-30 Hz bands in the contralateral motor cortex compared to controls.
• Bidirectional connectivity between the parietal and contralateral motor cortex (12-30 Hz) was decreased in essential tremor patients.
• Worsening tremor with increased visual feedback correlated with 4-12 Hz activity in the contralateral motor cortex.

Conclusions:

• Essential tremor is associated with diminished motor cortex power and reduced parietal-motor cortical connectivity.
• Findings suggest that cortico-cortical pathways, specifically the parietal-motor pathway, are involved in the network-level disturbances of essential tremor.
• The study highlights the utility of comparing group differences in motor cortex activity across feedback conditions for distinguishing essential tremor.