Abstract
Epilepsy is a chronic brain disease with dysfunctional brain networks, and electroencephalography (EEG) is an important tool for epileptogenic zone (EZ) identification, with rich information about frequencies. Different frequency oscillations have different contributions to brain function, and cross-frequency coupling (CFC) has been found to exist within brain regions. Cross-channel and inter-channel analysis should be both focused because they help to analyze how epilepsy networks change and also localize the EZ. In this paper, we analyzed long-term stereo-electroencephalography (SEEG) data from 17 patients with temporal lobe epilepsy. Single-channel and cross-channel CFC features were combined to establish functional brain networks, and the network characteristics under different periods and the localization of EZ were analyzed. It was observed that theta–gamma phase amplitude coupling (PAC) within the electrodes in the seizure region increased during the ictal (p < 0.05). Theta–gamma and delta–gamma PAC of cross-channel were enhanced in the early and mid-late ictal, respectively. It was also found that there was a strong cross-frequency coupling state between channels of EZ in the functional network during the ictal, along with a more regular network than interictal. The accuracy rate of EZ localization was 82.4%. Overall, the combination of single-channel and multi-channel cross-band coupling analysis can help identify seizures and localize EZ for temporal lobe epilepsy. Rhythmic coupling reveals a relationship between the functional network and the seizure status of epilepsy.
Highlights
Epilepsy is one of the most common neurological disorders, with ∼70 million patients worldwide
We found that the delta–gamma phase amplitude coupling (PAC) in patients, whose seizures ended within 2 min of the ictal period, had a sudden increase in the middle- and late-ictal
Based on the dynamic functional network extracted by crossfrequency PAC, we found that the network became more regular during the ictal, and the seizure features spread from local to global and focus on the epileptogenic zone (EZ)
Summary
Epilepsy is one of the most common neurological disorders, with ∼70 million patients worldwide. Cross-frequency coupling (CFC), which is a dynamic interaction between neural oscillations in different frequency bands, is closely related to memory, perception, and other brain functions. It provides a new perspective on a variety of physiological characteristics [10, 11]. Few studies have examined the extraction of network features from cross-channel coupling to observe changes in coupling relationships between regional channels during seizures. We prefer to effectively identify EZ channels and seizure propagation processes from all the detected channels in patients than to discuss coupling feature changes within local brain regions. The location of the epileptogenic zone and the changing pattern of information transmission in the network during the seizure were analyzed by complex graph theory to aid diagnosis and treatment
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