Distinct Spectral and Directional Thalamocortical Network Dynamics Define Focal Seizure Evolution.

Area of Science:

• Neuroscience
• Epilepsy Research
• Neuromodulation

Background:

• Neuromodulation targeting thalamic nuclei is a growing treatment for drug-resistant focal epilepsy.
• Limited human intracranial EEG studies exist on thalamocortical interactions during seizures.

Purpose of the Study:

• To define frequency-specific thalamocortical network dynamics from seizure onset to termination.
• To compare thalamocortical and cortico-cortical network activation.
• To assess if thalamic EEG features can classify seizure states for adaptive neuromodulation.

Main Methods:

• Retrospective analysis of stereo-EEG recordings from 19 epilepsy patients with thalamic and cortical sampling.
• Computation of spectral power, imaginary coherence, and Granger causality in slow, beta, and gamma bands.
• Training random forest classifiers using thalamic features to distinguish ictal from non-ictal states.

Main Results:

• Thalamic involvement was observed at seizure onset (81.2%) and increased by termination.
• Thalamocortical connectivity in slow and beta bands increased throughout seizures.
• Seizure state classification achieved high accuracy (AUC ~0.83) using thalamic spectral power and connectivity features.

Conclusions:

• Coordinated, frequency- and direction-specific thalamocortical network dynamics during seizures were defined.
• Slow and beta-band thalamocortical interactions are key targets for adaptive, closed-loop neuromodulation.
• Findings provide a mechanistic basis for optimizing seizure outcomes through thalamic neuromodulation.