PhD Scientific Days 2025

Poster Session I. - Q: Neurosciences

Intracortical mechanisms of after-discharges elicited by intracranial 50 Hz stimulation of epileptic patients

Name of the presenter

Szabó Johanna Petra

Institute/workplace of the presenter

Semmelweis University Clinic for Neurosurgery and Neurointervention

Authors

Johanna Petra Szabó¹, Boglárka Hajnal¹, Anna Sákovics¹, Loránd Erőss¹, Dániel Fabó²

1: Semmelweis University Clinic for Neurosurgery and Neurointervention
2: Semmelweis University Institute of Behavioural Sciences

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 poorly understood.
Our goal was to delineate cortical domain-specific characteristics of polyspike burst type ADs derived from intracranial macro- and microelectrode recordings. Our study examines the data of 7 drug-resistant epileptic patients undergoing presurgical evaluation with subdural grid electrodes, presenting ADs after 50 Hz stimulation. Simultaneously, laminar multielectrode arrays (LME) were implanted in the hypothesized epileptogenic zone.
Recordings were evaluated during stimulation (n = 6) and ADs (n = 5). We examined 989 stimulation events along with 50 AD-series with overall 797 AD events. Stimulation elicited either increased (81/989), decreased (430/989) or no change (189/989) in multi-unit activity (MUA), depending on the localization of stimulated site relative to the LME. More pronounced change in MUA predicted AD appearance. Additionally, non AD-generating events showed higher MUA when stimulating an otherwise AD-producing site compared to regions where no ADs emerged.
ADs proved to be very localized, detectable changes were found on LME in 17/50 series. The initial AD spikes, associated with infragranular sinks and prominent MUA, were followed by an upper-middle layer wave gradually extending to deep layers.
In sum, stimulation induces excitation in cortical neurons, accompanied by pronounced surround inhibition. The magnitude of this effect is related to the cortical susceptibility to generate ADs. ADs engage cortical layers in a specific sequence. A better understanding of stimulation-dependent neural dynamics may shed light to epileptogenic process within the cortex.
Supported by the EKÖP-2024-205 New National Excellence Program of the Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund.