TABLE 1.

Overview of passive and active markers of cortical excitability.

	Passive			Active
	Spikes	HFOs	Background EEG	Single pulse	Train of pulses
Current use	Clinical evaluation of the irritative zone for surgical planning		Research	Research	Trigger clinical seizures for surgical planning
What is measured	Visual identification of spikes Spike quantity and network	Visual identification of HFOs HFO quantity and network	Spectral measures Connectivity measures	CCEP amplitude Triggered epileptiform responses Connectivity measures	Visual identification of seizure onset
What is localized	Spike zone	HFO zone	Not established	Not established	Seizure onset zone
Monitoring over time	Strong modulation by brain states: frequency, amplitude, and propagation variable across sleep– wake, circadian, and multidien cycles			Not established	Not established
Modulation by ASMs	Expected decrease	Expected decrease	Not established	Expected decrease in excitability	Expected increase in seizure threshold

Abbreviations: ASM, antiseizure medication; CCEP, corticocortical evoked potential; EEG, electroencephalogram; HFO, high-frequency oscillation.