Subtype- and Phase-Specific Slow Oscillations Differentially Modulate Interictal Spikes in Human Epilepsy
Abstract number :
3.141
Submission category :
2. Translational Research / 2A. Human Studies
Year :
2025
Submission ID :
802
Source :
www.aesnet.org
Presentation date :
12/8/2025 12:00:00 AM
Published date :
Authors :
Presenting Author: Mahmoud Alipour, PhD – University of Chicago
David Satzer, MD – University of Chicago
Rationale: Slow oscillations (SOs; 0.5–1.5 Hz) during non-REM sleep are known to support memory consolidation but are also increasingly recognized as permissive to epileptic discharges. These rhythms are not uniform; based on their spatiotemporal dynamics, SOs can be classified into Local, Frontal, and Global subtypes. Global SOs, which propagate broadly across the cortex, are linked to sleep spindles and support memory via long-range information transfer—a feature not observed in other SO subtypes. In contrast, SOs associated with interictal spikes (IISs) often exhibit high amplitude in the frontal cortex—a characteristic of both Frontal and Global SOs. This contrast suggests that while some SO subtypes may promote cognitive function, others may facilitate pathological activity. Differentiating SO subtypes and their specific contributions to IIS occurrence is therefore critical. Such insights may guide neuromodulation to suppress epileptiform activity while preserving memory-supportive SOs. Emerging evidence also implicates thalamic structures—particularly the centromedian (CM) nucleus—in the coordination of cortical SOs. The thalamus may not only participate in SO propagation but also modulate their functional impact. Yet, the subtype- and phase-specific role of SOs in shaping IIS activity across both cortical and thalamic networks remains largely unexplored.
Methods: We analyzed 24-hour simultaneous scalp EEG and stereo-EEG (SEEG) recordings from a patient with drug-resistant epilepsy across three nights. SOs were detected and classified into Frontal or Global subtypes based on propagation patterns. IISs were detected using an algorithm based on IFCN criteria and manually reviewed. We examined the temporal relationship between IISs and SO subtype/phase in both seizure onset zone (SOZ) and CM thalamus contacts.
Results: Preliminary data showed that 88.2% of IISs in SOZ structures occurred during Frontal SOs, compared to only 11.8% during Global SOs. IISs were significantly more likely to occur during the SO up-state (63.1%) than the down-state (36.9%; p < 0.01, partial η² = 0.13; Figure 1A). This Frontal dominance—especially during the up-state—was consistent across SOZ structures (Figure 1B). In the CM thalamus, 72.1% of IISs were time-locked to scalp SOs (Figure 1C), indicating strong thalamocortical synchronization. Moreover, CM IISs were significantly more frequent during the up-state of Frontal SOs than in any other condition (p < 0.01, Cohen’s d = 0.28; Figure 1D).
Translational Research