Identifying site- and stimulation-specific TMS-evoked EEG potentials using a quantitative cosine similarity metric

Michael Freedberg; Jack A Reeves; Sara J Hussain; Kareem A Zaghloul; Eric M Wassermann

doi:10.1371/journal.pone.0216185

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Identifying site- and stimulation-specific TMS-evoked EEG potentials using a quantitative cosine similarity metric

Journal article

Open access

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Identifying site- and stimulation-specific TMS-evoked EEG potentials using a quantitative cosine similarity metric

Michael Freedberg, Jack A Reeves, Sara J Hussain, Kareem A Zaghloul and Eric M Wassermann

PloS one, Vol.15(1), p.e0216185

01/01/2020

DOI: 10.1371/journal.pone.0216185

PMCID: PMC6957143

PMID: 31929531

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Abstract

The ability to interpret transcranial magnetic stimulation (TMS)-evoked electroencephalography (EEG) potentials (TEPs) is limited by artifacts, such as auditory evoked responses produced by discharge of the TMS coil. TEPs generated from direct cortical stimulation should vary in their topographical activity pattern according to stimulation site and differ from responses to sham stimulation. Responses that do not show these effects are likely to be artifactual. In 20 healthy volunteers, we delivered active and sham TMS to the right prefrontal, left primary motor, and left posterior parietal cortex and compared the waveform similarity of TEPs between stimulation sites and active and sham TMS using a cosine similarity-based analysis method. We identified epochs after the stimulus when the spatial pattern of TMS-evoked activation showed greater than random similarity between stimulation sites and sham vs. active TMS, indicating the presence of a dominant artifact. To do this, we binarized the derivatives of the TEPs recorded from 30 EEG channels and calculated cosine similarity between conditions at each time point with millisecond resolution. Only TEP components occurring before approximately 80 ms differed across stimulation sites and between active and sham, indicating site and condition-specific responses. We therefore conclude that, in the absence of noise masking or other measures to decrease neural artifact, TEP components before about 80 ms can be safely interpreted as stimulation location-specific responses to TMS, but components beyond this latency should be interpreted with caution due to high similarity in their topographical activity pattern.

Adult

Brain Mapping

Electroencephalography

Evoked Potentials, Auditory - physiology

Female

Healthy Volunteers

Humans

Male

Motor Cortex - physiology

Parietal Lobe - physiology

Transcranial Magnetic Stimulation

Young Adult

Details

Title: Subtitle: Identifying site- and stimulation-specific TMS-evoked EEG potentials using a quantitative cosine similarity metric
Creators: Michael Freedberg - Henry M. Jackson Foundation
Jack A Reeves - National Institute of Neurological Disorders and Stroke
Sara J Hussain - National Institute of Neurological Disorders and Stroke
Kareem A Zaghloul - National Institute of Neurological Disorders and Stroke
Eric M Wassermann - National Institute of Neurological Disorders and Stroke
Resource Type: Journal article
Publication Details: PloS one, Vol.15(1), p.e0216185
DOI: 10.1371/journal.pone.0216185
PMID: 31929531
PMCID: PMC6957143
NLM abbreviation: PLoS One
ISSN: 1932-6203
eISSN: 1932-6203
Language: English
Date published: 01/01/2020
Academic Unit: Psychiatry; Health, Sport, and Human Physiology
Record Identifier: 9984948041202771

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