Table 1.

Novel approaches to approximate the epileptogenic zone from interictal intracranial EEG

Recording style	Potential biomarkers	The characteristics of the method
Resting-state EEG	High-frequency oscillation (HFO): 80-500 Hz	- HFO reflects cortical hyperexcitability. - HFO indicates the excitatory activity of pyramidal cells.
Resting-state EEG	Gamma oscillation regularity (GOR): 30-80 Hz	- Increased GOR (i.e., lower entropy) reflects cortical inhibition. - GOR indicates synchronization of inhibitory interneurons through GABAergic activity.
Evoked responses by SPES	CCEP connectivity (Remote region)	- Increased internal functional connectivity can be observed within the epileptogenic region. - Increased inhibitory input from the non-epileptogenic to ictogenic regions can also be observed.
Evoked responses by SPES	CCEP excitability (Neighboring region)	- Local cortical excitability is demonstrated as enhanced N1 amplitudes and increased HFOs overriding N1 waveforms close to the stimulation site.

CCEP, corticocortical evoked potential; EEG, electroencephalography; HFO, High-frequency oscillation; GABA, gamma-aminobutyric acid; SPES, single-pulse electrical stimulation