Evidence for Consolidation of Neuronal Assemblies after Seizures in Humans

Abstract

Continuous wide-bandwidth recordings from patients undergoing intracranial monitoring for drug-resistant epilepsy revealed reactivation of seizure-related neuronal activity during subsequent SWS, but not wakefulness. Those neuronal assemblies that were most strongly activated during seizures showed the largest correlation changes, suggesting that consolidation selectively strengthened neuronal circuits activated by seizures. These results suggest that seizures "hijack" physiological learning mechanisms and also suggest a novel epilepsy therapy targeting neuronal dynamics during post-seizure sleep.

Behavioral state classification in epileptic brain using intracranial electrophysiology

“…Determination of AW and SWS behavioral states using intracranial electrodes is motivated by potential applications for real-time behavioral state classification in implanted devices providing seizure forecasting (Cook et al 2013; Brinkmann et al 2015; Brinkmann et al 2016) and state dependent therapeutic stimulation (Bower et al 2015). We explored the feasibility of classification between two distinct behavioral states, AW and SWS, and demonstrated at the group level, patient level, and single electrode level that iEEG spectral bands can be used for automated classification using supervised learning in SVM with only ten minutes of AW and SWS data.…”

“…Slow-wave sleep (N3) was scored when high-voltage (>75 uV), low frequency delta (0.5 – 2 Hz) activity on scalp EEG was present in at least 20% of the epoch (i.e., at least 6 s within a 30 s epoch) in the frontal derivations using conventional International 10–20 System electrode placements (FP1, FP2, FZ, F3, F4, CZ, C3, C4, O1, O2, and Oz). A similar approach has been used in previous studies (Bower et al 2015, Klimes et al 2016). …”

“…Automated behavioral state classification should prove useful for implantable epilepsy devices, and would make possible behavioral-state-dependent seizure prediction (Cook et al 2013; Brinkmann et al 2015; Brinkmann et al 2016; Ramgopal et al 2014), and electrical stimulation therapies (Bower et al 2015; Lundstrom, B.N et al 2016; Salanova et al 2015). The effect of behavioral state on human scalp EEG is the cornerstone of sleep scoring (Rechtschaffen and Kales 1968).…”

Slow wave sleep and accelerated forgetting

“…The normal temporal synchronisation between hippocampal activity, spindles and/or neocortical slow waves could be disturbed (Clemens et al., 2007, Holler and Trinka, 2015). Neocortical slow waves might also trigger chaotic hippocampal activity (Holler & Trinka, 2015), which could even reflect the pattern of prior epileptiform activity (Bower et al., 2015), rather than faithful memory reactivations. Finally, it may be that the SWS-associated brain activity patterns are entirely normal but that the memory reactivations exert a negative, rather than positive, effect on memory in this patient group.…”

The Emergence of Single Neurons in Clinical Neurology

“…Furthermore, in some circumstances, a striking reproducibility of neuronal spiking patterns across different seizures has also been reported (Truccolo et al, 2011); the degree to which this is a universal feature is actively being investigated. Implications of this reproducibility extend to an understanding of the long-lasting impact of seizures on neuronal activity (Bower et al, 2015). The renewed recognition of the heterogeneous roles that single neurons may play before, during, and after a seizure implies a new wave of opportunity for diagnostic and therapeutic approaches in epilepsy, and also serves to reinforce the clinical importance of ensembles of individual neurons which may be physically separated but critically linked by underlying collective dynamics.…”