PhD Scientific Days 2024

Budapest, 9-10 July 2024

Poster Session I - Neurosciences 2.

Intracortical Mechanisms of After-discharges Elicited by Intracranial 50 Hz Stimulation of Epileptic Patients


Johanna Petra Szabó1, Boglárka Hajnal1, Anna Sákovics1, Loránd Erőss2, Dániel Fabó1
1: Epilepsy Unit, Department of Neurosurgery and Neurointervention , Semmelweis University, Budapest, HU
2: Functional Neurosurgery Unit, Department of Neurosurgery and Neurointervention , Semmelweis University, Budapest, HU

Text of the abstract

Rhythmic stimulation-induced discharges, known as after-discharges (AD), have long been correlated with epileptogenic processes. Nevertheless, the latent neuronal processes are still unknown.
Our goal was to delineate cortical domain-specific characteristics of ADs derived from intracranial macro- and microelectrode recordings.
Our study examines the data of 12 drug-resistant epileptic patients undergoing presurgical evaluation with subdural grid electrodes, presenting prominent ADs elicited by 50 Hz stimulation. Simultaneously, laminar multielectrode arrays (LME) were also implanted in the hypothesized EZ. Polyspike type ADs were identified on the macroelectrode recordings of all patients. Four patients with LMEs placed near an AD-presenting electrode, were selected for further analysis.
We have examined both macro- and microelectrode recordings of 36 series of ADs with overall 551 AD events. ADs detected on macroelectrode recordings proved to be very localised, only LMEs located in proximity (<1 cm) were able to register visible discharges. ADs variably engaged both supra- and infragranular layers. Current-source density revealed a prominent sink in the infragranular domain. MUA appeared to start in middle layers, propagating to both lower and higher domains. High frequencies mostly occurred in lower layers.
In sum, our data suggests that beside infragranular domain, upper layers might also participate in AD generation.