A widespread visually-sensitive functional network relates to symptoms in essential tremor

Area of Science:

• Neuroscience
• Neurology
• Medical Imaging

Background:

• Essential tremor (ET) is a neurological disorder primarily affecting the upper extremities, often linked to the cerebello-thalamo-cortical pathway.
• While brain activity (BOLD signal) in this pathway is associated with ET, behavioral evidence suggests visual feedback may also influence tremor severity.

Purpose of the Study:

• To investigate the direct impact of manipulating visual feedback on tremor in essential tremor patients during functional MRI.
• To explore the association between altered visual feedback, brain activity (BOLD signal and entropy), and tremor severity within and beyond the cerebello-thalamo-cortical pathway.

Main Methods:

• Functional MRI (fMRI) was used to measure brain activity while essential tremor patients and controls performed a grip force task with manipulated visual feedback.
• Bidirectional stepwise multiple regression analysis was employed to identify brain regions associated with tremor severity.
• Tremor severity was assessed both during the fMRI task and clinically using the Fahn, Tolosa, Marin Tremor Rating Scale.

Main Results:

• Increased visual feedback exacerbated tremor in essential tremor patients within the 4-12 Hz range.
• This tremor exacerbation correlated with abnormal changes in BOLD signal amplitude and entropy in the cerebello-thalamo-motor cortical pathway, extending to visual and parietal areas.
• A widespread functional network, beyond the cerebello-thalamo-motor pathway, was significantly associated with both imaging-measured and clinical tremor severity, but not with force error reduction.

Conclusions:

• The severity of essential tremor is influenced by a widespread functional network, which is exacerbated by increased visual feedback.
• This network is clinically relevant, correlating with established tremor rating scales, and highlights the potential impact of visual input on tremor.
• Findings suggest that reducing visual feedback in technology design may help mitigate tremor in essential tremor patients.