Single pulse electrical stimulation (SPES) is an investigational direct electrical stimulation (DES) pattern. Direct cortical stimulation applied at a frequency of ∼1Hz can probe cortico-cortical connections by averaging electrocorticogram time-lock to the stimuli.

Paired-pulse stimulation paradigm associates a conditioning and a test stimulation to induce intracortical inhibition or facilitation by modifying the response amplitude.

Stepwise frequency stimulation is a DES protocol that incrementally increases the stimulation frequency, starting from a lower to higher.

Burst stimulation is a DES patterned repetitive stimulation method; it represents a "more precise" and "smarter" electrical stimulation paradigm. Within a group, high-frequency pulses are emitted, and between groups, low-frequency pulses are delivered. This pattern of pulse delivery more closely mimics the physiological activity of neurons within the brain.

Investigators use single-pulse electrical stimulations at 1Hz to elicit cortico-cortical evoked potentials

Investigators calculate normalized the Modulation Factors of single-pulse electrical stimulation, paired electrical stimulation, stepwise electrical stimulation, and burst electrical stimulation patterns using (stimulation-pre-stimulation)/(stimulation + pre-stimulation)

Using SEEG-implanted electrodes, the investigators applied electrical stimulation single-pulse electrical stimulation, paired electrical stimulation, stepwise electrical stimulation, and burst electrical stimulation while observing and recording EEG power changes across six spectral frequency bands during the pre-stimulation, stimulation, and post-stimulation periods.

EEG Frequency Bands delta (1-4 Hz) theta (5-8 Hz) alpha (9-12 Hz) beta (13-30 Hz) low gamma (31-70 Hz) high gamma (71-150 Hz)

To estimate functional connectivity through the oscillatory synchrony of two brain regions, phase locking value (PLV) provides a measure of inter-regional synchrony based on phase difference between the paired signals.