Abstract
Objective. Direct electrical stimulation of the brain through intracranial electrodes is currently used to probe the epileptic brain as part of pre-surgical evaluation, and it is also being considered for therapeutic treatments through neuromodulation. In order to effectively modulate neural activity, a given neuromodulation design must elicit similar responses throughout the course of treatment. However, it is unknown whether intracranial electrical stimulation responses are consistent across sessions. The objective of this study was to investigate the within-subject, cross-session consistency of the electrophysiological effect of electrical stimulation delivered through intracranial electroencephalography (iEEG). Approach. We analysed data from 79 epilepsy patients implanted with iEEG who underwent brain stimulation as part of a memory experiment. We quantified the effect of stimulation in terms of band power modulation and compared this effect from session to session. As a reference, we made the same measurements during baseline periods. Main results. In most sessions, the effect of stimulation on band power could not be distinguished from baseline fluctuations of band power. Stimulation effect was consistent in a third of the session pairs, while the rest had a consistency measure not exceeding the baseline standards. Cross-session consistency was highly correlated with the degree of band power increase, and it also tended to be higher when the baseline conditions were more similar between sessions. Significance. These findings can inform our practices for designing neuromodulation with greater efficacy when using direct electrical brain stimulation as a therapeutic treatment.
Highlights
Introduction ceAbout 35% of patients with epilepsy are drug-resistant and require additional treatment [1, 2]
Direct electrical stimulation is currently used in three ways: first, functional mapping of the cortex so that eloquent cortical areas are preserved in resective epilepsy surgery [3, 4]; second, measuring the “epileptogenicity” of the stimulated and surrounding areas [5]; third, exploring the neuromodulatory potential of direct electrical stimulation which can be the basis for therapeutic interventions
We showed that the within-subject, cross-session consistency of stimulation effect, as measured by band power modulation, is relatively low in a group of 36 subjects who had multiple stimulation sessions through intracranial electroencephalography (iEEG)
Summary
About 35% of patients with epilepsy are drug-resistant and require additional treatment [1, 2]. In this context, direct electrical stimulation through intracranial electroencephalography (iEEG) has become an invaluable tool for clinicians. In this work we will focus on the neuromodulatory potential of intracranial electric stimulation. To achieve any therapeutic goals, the effect of stimulation should be consistent across multiple sessions in each patient [9]. The consistency of iEEG stimulation effect has not been studied systematically
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