Phase-amplitude coupling of ripple activities during seizure evolution with theta phase

Abstract

High-frequency activities (HFAs) and phase-amplitude coupling (PAC) are gaining attention as key neurophysiological biomarkers for studying human epilepsy. We aimed to clarify and visualize how HFAs are modulated by the phase of low-frequency bands during seizures. MethodsWe used intracranial electrodes to record seizures of symptomatic focal epilepsy (15 seizures in seven patients). Ripples (80-250 Hz), as representative of HFAs, were evaluated along with PAC. The synchronization index (SI), representing PAC, was used to analyze the coupling between the amplitude of ripples and the phase of lower frequencies. We created a video in which the intracranial electrode contacts were represented by circles that were scaled linearly to the power changes of ripple. ResultsThe main low frequency band modulating ictal-ripple activities was the θ band (4-8 Hz), and after completion of ictal-ripple burst, δ (1-4 Hz)-ripple PAC occurred. The video showed that fluctuation of the diameter of these circles indicated the rhythmic changes during significant high values of θ-ripple PAC. ConclusionsWe inferred that ripple activities occurring during seizure evolution were modulated by θ rhythm. In addition, we concluded that rhythmic circles' fluctuation presented in the video represents the PAC phenomenon. Our video is thus a useful tool for understanding how ripple activity is modulated by the low-frequency phase in relation with PAC.

Motor and sensory cortical processing of neural oscillatory activities revealed by human swallowing using intracranial electrodes

“…Epilepsy studies reported a positive correlation between coupling values and high-frequency amplitude (Hashimoto et al, 2021a;Weiss et al, 2016). We showed the continuous positive correlation between…”

“…EEG studies suggest that q oscillations are related to both sensory and motor behaviors (Tomassini et al, 2017) and a general property of brain activity (Ramayya et al, 2020). In the epileptic brain, the hippocampal q rhythm was increased (Kitchigina and Butuzova, 2009) and seizure-related HFA was coupled with q band (Hashimoto et al, 2020b(Hashimoto et al, , 2021a. The q oscillations are involved in both sensory and motor neural processing, and both physiological and pathological neural processing, and in this study, we provide a new insight into the sensory-related q-HG coupling.…”

“…HG activity is a key oscillation that reflects the neural processing and shows better functional localization than lower-frequency activity (Canolty et al, 2006;Crone et al, 1998a;Miller et al, 2007). HG activities are physiological activities; pathological high-frequency activities (HFAs) have been reported in epilepsy (Ayoubian et al, 2013;Hashimoto et al, 2021a;Jacobs et al, 2009;Matsumoto et al, 2013).…”

“…PAC plays different functional roles in cortical processing, such as motor execution (Yanagisawa et al, 2012b) and somatosensory processing (Lakatos et al, 2008). PAC is thought to be related to physiological neural processing, whereas PAC has also been reported to be associated with pathological neural processing, such as epileptic seizures (Hashimoto et al, 2020b(Hashimoto et al, , 2021a) and Parkinson's disease (de Hemptinne et al, 2015).…”

Phase-amplitude coupling between infraslow and high-frequency activities well discriminates between the preictal and interictal states

“…PAC analysis measures the degree of synchronization between the phases with low-frequency oscillation and high-frequency amplitude 18 . Ictal HFA amplitudes coupled with δ 19 , 20 , θ 21 , 22 , and α 21 phases, and β-HFA coupling are reported as useful markers for seizure detection 23 . Moreover, coupling θ waves with HFOs has been reported to well discriminate normal brain regions from the seizure onset zone (SOZ) 24 .…”