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How Thalamo-Cortical Loops Modulate Cortico-Cortical Evoked Potentials?
Odile Feys1,2, Samuel Medina Villalon3,4, Christian-George Bénar4
1Department of Epileptology and Cerebral Rhythmology, Timone Hospital - APHM, Marseille, France. odile.feys@pennmedicine.upenn.edu.
Higher-order thalamic nuclei, specifically the pulvinar, actively shape cortico-cortical evoked potentials (CCEPs) through iterative cortico-thalamic loops. This challenges the view of CCEPs as solely direct cortical connections.
Area of Science:
- Neuroscience
- Systems Neuroscience
- Epilepsy Research
Background:
- The origin of late cortico-cortical evoked potentials (CCEPs) has been linked to the thalamus.
- The specific role of higher-order thalamic nuclei in modulating CCEP dynamics via cortico-thalamo-cortical loops is not well understood.
Purpose of the Study:
- To investigate the involvement of higher-order thalamic nuclei in CCEP generation and modulation.
- To explore the dynamics of cortico-thalamo-cortical interactions in shaping CCEP responses.
Main Methods:
- Analysis of stereoelectroencephalography (SEEG) recordings from epilepsy patients undergoing cortical stimulation.
- Identification of cortico-thalamic evoked potentials (CTEPs) and CCEPs using t-tests.
- Assessment of effective connectivity using nonlinear h2 correlation and intertrial correlations.
Main Results:
- Significant CTEPs were identified in the pulvinar following cortical stimulation.
- Iterative recruitment of cortico-thalamic loops was observed, with alternating corticothalamic and thalamocortical connectivity.
- Delayed thalamocortical connectivity suggested polysynaptic pathways, indicating thalamic influence across different timescales.
Conclusions:
- Cortico-thalamic loops, involving higher-order thalamic nuclei, iteratively shape CCEP dynamics at both short and long timescales.
- These findings challenge the traditional view of CCEPs as purely direct cortical pathways.
- Higher-order thalamic nuclei actively modulate cortico-cortical connectivity, impacting CCEP interpretation and neuromodulation mechanisms in epilepsy.
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