Band power modulation through intracranial EEG stimulation and its cross-session consistency

TL;DR

This study investigates the consistency of intracranial EEG stimulation effects across sessions, revealing that stimulation responses are often variable and only partially consistent, which impacts neuromodulation therapy design.

Contribution

It provides the first systematic analysis of cross-session consistency of intracranial stimulation effects, highlighting factors influencing reliability for therapeutic applications.

Findings

Stimulation effects on band power are often indistinguishable from baseline fluctuations.

Only about one-third of session pairs show higher consistency than baseline standards.

Greater consistency is linked to stronger positive stimulation effects and similar baseline conditions.

Abstract

Background: 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. It is still unknown, however, how consistent intracranial direct electrical stimulation responses are across sessions, to allow effective neuromodulation design. Objective: To investigate the cross-session consistency of the electrophysiological effect of electrical stimulation delivered through intracranial EEG. Methods: We analysed data from 79 epilepsy patients implanted with intracranial EEG 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 applied the same measures during baseline periods. Results: In most sessions, the effect of stimulation on band power could not be distinguished from baseline fluctuations of band power. Stimulation effect was also not consistent across sessions; only a third of the session pairs had a higher consistency than the baseline standards. Cross-session consistency is mainly associated with the strength of positive stimulation effects, and it also tends to be higher when the baseline conditions are more similar between sessions. Conclusion: These findings can inform our practices for designing neuromodulation with greater efficacy when using direct electrical brain stimulation as a therapeutic treatment.