Local Sleep Slow-Wave Activity Colocalizes With the Ictal Symptomatogenic Zone in a Patient With Reflex Epilepsy: A High-Density EEG Study

Eric W. Moffet, Ruben Verhagen, Benjamin Jones, Graham Findlay, Elsa Juan, Tom Bugnon, Armand Mensen, Mariel Kalkach Aparicio, Rama Maganti, Aaron F. Struck, Giulio Tononi, Melanie Boly*

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


Background: Slow-wave activity (SWA) during non-rapid eye movement (NREM) sleep reflects synaptic potentiation during preceding wakefulness. Epileptic activity may induce increases in state-dependent SWA in human brains, therefore, localization of SWA may prove useful in the presurgical workup of epileptic patients. We analyzed high-density electroencephalography (HDEEG) data across vigilance states from a reflex epilepsy patient with a clearly localizable ictal symptomatogenic zone to provide a proof-of-concept for the testability of this hypothesis. Methods: Overnight HDEEG recordings were obtained in the patient during REM sleep, NREM sleep, wakefulness, and during a right facial motor seizure then compared to 10 controls. After preprocessing, SWA (i.e., delta power; 1–4 Hz) was calculated at each channel. Scalp level and source reconstruction analyses were computed. We assessed for statistical differences in maximum SWA between the patient and controls within REM sleep, NREM sleep, wakefulness, and seizure. Then, we completed an identical statistical comparison after first subtracting intrasubject REM sleep SWA from that of NREM sleep, wakefulness, and seizure SWA. Results: The topographical analysis revealed greater left hemispheric SWA in the patient vs. controls in all vigilance states except REM sleep (which showed a right hemispheric maximum). Source space analysis revealed increased SWA in the left inferior frontal cortex during NREM sleep and wakefulness. Ictal data displayed poor source-space localization. Comparing each state to REM sleep enhanced localization accuracy; the most clearly localizing results were observed when subtracting REM sleep from wakefulness. Conclusion: State-dependent SWA during NREM sleep and wakefulness may help to identify aspects of the potential epileptogenic zone. Future work in larger cohorts may assess the clinical value of sleep SWA to help presurgical planning.

Original languageEnglish
Article number549309
Pages (from-to)1-8
Number of pages8
JournalFrontiers in Systems Neuroscience
Issue numberOctober
Publication statusPublished - 21 Oct 2020


This work was supported by NINDS 1R03NS096379 to MB, Swiss National Foundation grants 168437 and 177873 to EJ, funding from the Dutch Research Council to RV, and Tiny Blue Dot Foundation to MB and GT.

FundersFunder number
Dutch Research Council
Swiss National Foundation168437, 177873
Tiny Blue Dot Foundation
National Institute of Neurological Disorders and Stroke1R03NS096379
Nederlandse Organisatie voor Wetenschappelijk Onderzoek


    • delta power
    • high-density EEG
    • reflex epilepsy
    • sleep
    • slow-wave activity


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