ECoG high-gamma activity peak during speech production increases the ECS effect
Poster No:
29
Submission Type:
Abstract Submission
Authors:
Christoph Kapeller1, Kyousuke Kamada2, Mostafa Mohammadpour1, Christoph Guger1
Institutions:
1g.tec medical engineering GmbH, Schiedlberg, Austria, 2Megumino Hospital, Eniwa, Hokkaido
First Author:
Co-Author(s):
Introduction:
Electrical cortical stimulation (ECS) has the capability to induce behavioral and cognitive changes through precise modulation of targeted brain regions. This phenomenon manifests in effects such as involuntary motor movements, visual distortions, and transient language impairments, particularly when specific brain areas related to motor control, vision, or language processing are targeted. Notably, the surgical removal of these regions often results in postoperative functional deficits, underscoring the importance of ECS as a preoperative and perioperative tool for functional mapping. In the context of language mapping, ECS serves as a benchmark for preserving speech function [1].
While established ECS protocols for language tasks exist, they are primarily based on empirical observations and adapted to individual patient variations. Therefore, it is crucial to have a comprehensive understanding of the causal relationship between stimulation parameters and resulting behavioral outcomes. Broadband high-gamma activity (HGA), detected through electrocorticography (ECoG), serves as an additional biomarker with superior spatial resolution, reflecting neural activity related to language [2, 3].
This study aimed to investigate whether the timing of ECS initiation during a naming task influences symptom frequency and how this timing aligns with the trajectory of HGA.
While established ECS protocols for language tasks exist, they are primarily based on empirical observations and adapted to individual patient variations. Therefore, it is crucial to have a comprehensive understanding of the causal relationship between stimulation parameters and resulting behavioral outcomes. Broadband high-gamma activity (HGA), detected through electrocorticography (ECoG), serves as an additional biomarker with superior spatial resolution, reflecting neural activity related to language [2, 3].
This study aimed to investigate whether the timing of ECS initiation during a naming task influences symptom frequency and how this timing aligns with the trajectory of HGA.
Methods:
Two epilepsy patients from Megumino Hospital, Japan, provided informed consent for the clinical ECS language mapping extension before brain surgery. Prior to ECS, a picture naming task was used to capture task-related HGA. Subsequent ECS identified stimulation sites inducing transient language impairments through 5-7mA stimulation. The site with the most pronounced HGA was selected for ECS with variable onsets (0.35 to 1 second post-picture onset). ECS, administered at 50Hz for 1 second, resulted in trial classifications as 'no symptom' or 'symptom' based on speech anomalies.
Results:
HGA peaked at 5.44 and 4.72 z-scores at 684 and 454 milliseconds for the first and second patients, respectively, with corresponding intervals of 383-955 and 333-764 milliseconds. Figure 1 shows the HGA together with the time-frequency maps of the the stimulation target area (ROI). The symptom occurrence in Figure 2 was 92% and 47% before the HGA peak for the first and second patients, decreasing to 37% and 13% post-peak
Conclusions:
Stimulation before the HGA peaks significantly reduced the response speed compared sham stimulation. This underscores the crucial interplay between speech production, HGA, and ECS efficacy. Moreover, faster-responding patients require earlier ECS, suggesting tailored protocols for efficient functional mapping, particularly in time-sensitive procedures like awake craniotomies.
Brain Stimulation:
Direct Electrical/Optogenetic Stimulation 1
Language:
Speech Production 2
Modeling and Analysis Methods:
Activation (eg. BOLD task-fMRI)
Neuroanatomy, Physiology, Metabolism and Neurotransmission:
Cortical Anatomy and Brain Mapping
Novel Imaging Acquisition Methods:
Multi-Modal Imaging
Keywords:
Aphasia
Cortex
ELECTROCORTICOGRAPHY
ELECTROPHYSIOLOGY
Language
Other - Electrical Stimulation
1|2Indicates the priority used for review
·Figure 2: Stimulation effect (left) and response time (right) with respect to HGA peak.
·Figure 1: Stimulation target area inside ROI with time-frequency map and HGA time course.
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[2] Wang, P., et al. (2021). Clinical applications of neurolinguistics in neurosurgery. Frontiers of medicine, 15(4), 562-574.
[3] Sonoda, M. et al. (2022). Naming-related spectral responses predict neuropsychological outcome after epilepsy surgery, Brain, Volume 145, Issue 2, Pages 517–530.