Thalamo-centric causal connectivity mapping in human brain with intracranial electrical stimulation
Dian Lyu1 (email@example.com), Josef Parvizi1; 1Department of Neurology and Neurological Sciences, Stanford University
In this study we explore the whole-brain causal connectivity with a central focus on the thalamus' role in shaping whole-brain connectivity motifs, investigated through multi-site stimulation and recording using deep intracranial electrodes. The study involved 27 participants with focal epilepsy and implanted electrodes. Whole-brain causal connectivity was examined by stimulating each bipolar channel while recording from others. The Uniform Manifold Approximation and Projection (UMAP) algorithm was employed to encode neural signals, utilizing time-variant power and inter-trial phase coherence spectrograms of stimulation evoked potentials (SEPs). Activation labeling was derived through semi-supervised learning, and group-level supervised UMAP was used to map activated spectrograms to anatomical identities. Neural features 1&2, characterized by gamma/beta and high theta respectively, were distinguished in cortical stimulations. A unique third cluster (Feature3) emerged in thalamus stimulations, revealing delayed and persistent theta oscillations. Whole-brain causal connectivity matrices unveiled modularity in adjacent areas within hemispheres (Feature-1), widespread representations across hemispheres (Feature-2), and widespread delayed thalamocortical feedback (Feature-3). Comparing thalamic subdivisions, anterior thalamus exhibited recurrent connectivity with the frontal areas, while the posterior thalamus showed stronger connections with parietal and occipital areas. In conclusion, the study encoded whole-brain stimulation-evoked potentials into three neural features, representing direct cortical connectivity, indirect connectivity via cortex, and thalamocortical feedback. Thalamus was found to receive direct connectivity from the whole brain, while its direct cortical projection was hemisphere-limited. Indirect thalamocortical feedback, persisting in cortical signals for approximately 200 ms with a late onset (>165ms upon stimulation), acts as a propagator of theta oscillations throughout the brain.
Topic Area: METHODS: Electrophysiology
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April 13–16 | 2024