Single pulse electrical stimulation to probe functional and pathological connectivity in epilepsy

Abstract

In the last decade, single pulse electrical stimulation (SPES) has been used as an investigational tool in the field of epilepsy surgery. Direct cortical stimulation applied at a frequency of ∼1 Hz can probe cortico-cortical connections by averaging electrocorticogram time-lock to the stimuli (2 x 20–30 trials). These evoked potentials that emanate from adjacent and remote cortices have been termed cortico-cortical evoked potentials (CCEPs). Although limited to patients undergoing invasive presurgical evaluations with intracranial electrodes, CCEP provides a novel way to explore inter-areal connectivity in vivo in the living human brain to probe functional brain networks such as language and cognitive motor networks. In addition to its impact on systems neuroscience, this method, in combination with 50 Hz electrical cortical stimulation, could contribute clinically to map the functional brain systems by tracking the cortico-cortical connections among the functional cortical regions in each individual patient. This approach may help identify the normal cortico-cortical network within pathology as well as reveal connections that might arise from neural plasticity. Because of its high practicality, it has been recently applied for intraoperative monitoring of the functional brain networks for patients with brain tumor. With regard to epilepsy, SPES has been used for the two major purposes, one to probe cortical excitability of the focus, namely, epileptogenicity, and the other to probe seizure networks. Both early (i.e., CCEP) and delayed responses, and probably their high frequency oscillation counterparts, are regarded as a surrogate marker of epileptogenicity. With regards to its impact on the human brain connectivity map, worldwide collaboration is warranted to establish the standardized CCEP connectivity map as a solid reference for non-invasive connectome researches.

Evoked directional network characteristics of epileptogenic tissue derived from single pulse electrical stimulation

“…In a recent review, Matsumoto, Kunieda, and Nair (2017) suggested that the amplitude of the ERs in epileptogenic and “normal” tissue is higher when stimuli are applied to the SOZ (Enatsu, Piao, et al, 2012), but the distribution of these ERs is not adapted in the epileptogenic network. In this study, we did not investigate the amplitude of an ER, but we found specific network properties of epileptogenic tissue.…”

Illusory own body perceptions mapped in the cingulate cortex—An intracranial stimulation study

“…Multiple stimulation protocols were carried out routinely as part of the standard presurgical assessment (Trebuchon & Chauvel, ) using low frequency 1 Hz (Munari et al, ) and single‐pulse electrical stimulation (Donos, Mîndruţă, Ciurea, Mălîia, & Barborica, ; Matsumoto, Kunieda, & Nair, ), as well as high frequency 50 Hz (HFS; Bernier et al, ) direct electrical stimulation; however, only HFS was able to elicit clinical effects of changes in body perception. Therefore, functional mapping of the cortex was systematically reviewed using direct electrical high frequency stimulation of the brain delivered at a rate of 50 Hz (Figure c).…”

Human entorhinal cortex electrical stimulation evoked short‐latency potentials in the broad neocortical regions: Evidence from cortico‐cortical evoked potential recordings

“…The aim of CCEPs was to identify functional and seizure networks by stimulating the majority of implanted electrodes for research and clinical purposes (Kobayashi et al, ; Matsumoto, Kunieda, & Nair, ). We used the highest current intensity at which (a) the patient did not notice the stimulation and no apparent symptoms were evoked, (b) adjacent electrodes did not show excessive artifacts interfering with the recording, and (c) no afterdischarges were detected.…”