Enhanced Phase and Amplitude Synchronization Toward Focal Seizure Offset

Abstract

Recent studies involving individual neurons in the seizure focal and surrounding areas have established heterogeneous firing patterns in single cells. However, the patterns become more homogeneous approaching the seizure offset. In this article, we show that similar observations are possible from intracranial recording if the right quantitative or engineering techniques are used. We have observed an increase in Hilbert transformation-based phase synchronization in the focal electrocorticoencehalogram (ECoG) in the gamma band (30-40 Hz) towards the end of the majority of focal epileptic seizures. An amplitude correlation measure shows an enhanced principal component (and hence enhanced correlation among the channels involved) approaching the offset of the large majority of seizures. Surprisingly, there are seizures which show the enhanced phase synchronization approaching offset but no enhanced amplitude correlation during the same period and vice versa. This study shows that suitable computational tools can sometimes compensate for more expensive and technologically demanding data acquisition systems. A possible neurophysiological explanation behind the observed phenomenon is also presented.

Enhanced gamma band mutual information is associated with impaired consciousness during temporal lobe seizures

“…This trend has been observed in the gamma band, particularly by phase synchronization and mutual information. High synchronization leading to seizure termination has already been observed in multiple studies (Schindler et al, 2007;Jiruska et al, 2013;Prasad et al, 2013;Majumdar et al, 2014). During the course of this work, we have observed that high synchronization often persists beyond termination from least involved channels to SOZ in beta and gamma bands and impairs consciousness (results not presented).…”

A Peak Synchronization Measure for Multiple Signals

“…In fact evolution of synchronization across different channels during an epileptic seizure is a complex process. Synchronization is less at the onset of seizure, but more at the offset and even beyond as measured by phase synchronization and amplitude correlation [49], [50]. Quantitative outcomes of the two methods differ significantly and even some time contradicted each other (see ref.…”

NREM Sleep and Antiepileptic Medications Modulate Epileptiform Activity by Altering Cortical Synchrony

“…Using Shannon entropy method, ensemble phase synchronization 16 was computed between the 8 EEG channels (ie, F8-A1, F7-A2, T4-A1 and T3-A2, C4-A1 and C3-A1, O2-A1 and O1-A2) to study the peri-IED change in SI in patients having generalized epilepsy (JME). For patients having focal epilepsy (TLE and Ex-TLE), pairwise phase synchronization 17 was computed to study peri-IED change in SI between channels pairs of interest (ie, channel pairs that showed highest spike amplitude). The phase synchronization (SI) was analyzed in 4 different frequency bands, namely, delta, theta, alpha, and beta.…”

“…The mean and SD of SI in various categories has been tabulated ( Table 2). D. Beta (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) band. There were differences noted between study groups (P < .001), sleep stages (P < .001) as well as between IED and background period (P < .001).…”