EVALUATION OF SPONTANEOUS AND ELECTRICALLY EVOKED ELECTROPHYSIOLOGICAL PHENOMENA IN EPILEPTIC PATIENTS IMPLANTED WITH LAMINAR MICROELECTRODES
Hajnal Boglárka Zsófia
János Szentágothai Neurosciences
Dr. Bereczki Dániel
Egészségtudományi Kar, Budapest, Szentkirályi u. 12-14. I.emelet 1.07-es tanterem
2025-07-02 14:00:00
Clinical Neurological Research
Dr. Kovács Tibor
Dr. Fabó Dániel
Dr. Gulyás Szilvia
Dr. Meszéna Domokos
Dr. Bereczki Dániel
Dr. Lukács Melinda
Dr. Szatmári Szabolcs
Our study (9, 10) investigates the layer-specific dynamics of sleep spindles and cortico-cortical evoked potentials (CCEPs) in the human neocortex using intracranial laminar microelectrode (LME) and electrocorticography (ECoG) recordings from seven epileptic patients. The goal was to explore how these phenomena reflect thalamocortical and cortico-cortical processing in different cortical layers. Regarding sleep spindles, we found that spindles recorded in cortical layers are often localized events. However, in 50-80% of cases, spindles co-occur across adjacent layers, with larger spindles showing more frequent co-occurrence, and LME-ECoG co-occurrence decreased with greater distance between electrodes. While LME-only spindles were common, most ECoG spindles had corresponding LME spindles. This supports the idea that intracortical spindles are more localized than those detected by ECoG. We did not find distinct laminar profiles for different spindle subtypes (e.g., slow vs. fast spindles), suggesting that any differences between subtypes are more likely driven by local neuronal activity rather than selective contribution of different thalamocortical pathways. Single-unit activity (SUA) peaked during spindle troughs with a phase preference for the positive-negative LFPg transition, while multi-unit activity (MUA) exhibited an antiphase relationship with local field potentials (LFPs), consistent with previous findings. Overall, SUA and MUA were negatively correlated to LFP, with variations by patient, layer, and spindle type, indicating heterogeneous contributions to the local field potential across layers. In the analysis of CCEPs, we identified five major components: early (P1, N1), middle (P2, N2), and late (P3). Based on the laminar profile of CCEPs, we developed a hypothetical model to represent the sequence of intracortical activation during SPES-evoked potentials. Initially, layer V pyramidal neurons are depolarized (P1), creating a local feed-forward excitation (N1) that propagates to layers I-II, where it disrupts local inhibitory processes and contributes to the active inhibition observed in P2. This is followed by a sleep slow wave (SW)-like cycle, with a downstate reflecting widespread disfacilitation across all layers (N2) and an upstate (P3), with increased cell-firing. In conclusion, our research highlights that sleep spindle subtypes are influenced by local neuronal dynamics, not distinct thalamocortical pathways (9). CCEP components involve complex interactions across cortical layers, with late components resembling sleep slow waves, revealing that stimulation can evoke sleep-like cortical dynamics in awake states (10).
