Evidence map›Paper›PMID 33516859›Full record

Trial reportBrain stimulation

Pinging the brain with transcranial magnetic stimulation reveals cortical reactivity in time and space.

Sangtae Ahn, Flavio Fröhlich

Open access · goldAbstract readRandomized Controlled Trial
PubMed Full text at PMC Publisher
In one paragraph

Trial report in Brain stimulation. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 42 papers, 2 of them syntheses that pooled it.

0numbers the graph read from it
0cells of the map it votes in
42citing papers in PubMed, 2 pooled it
6.4field-weighted citation impact, top 3% of its field
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

42 citing papers in PubMed, 2 syntheses or guidelines pooled it, 88 citations in OpenAlex.

  1. Pooled it
  2. Pooled it
  3. Trial
  4. Article
  5. Review
  6. Clinical utility and prospective of TMS-EEG: Updated review from an international expert group.Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology · 2026
    Review
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  8. Review
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  15. Concurrent TMS-EEG to characterize cortical responses in the motor and prefrontal cortices in Parkinson's disease.Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics · 2025
    Article
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4 · The record

Corrections and comments

5 · Who and what money

Authors and funding

2 authors at 1 institution in 2 countries.

Sangtae AhnSchool of Electronics Engineering, Kyungpook National University, Daegu, 41566, South Korea; School of Electronic and Electrical Engineering, Kyungpook National University, Daegu, 41566, South Korea; Carolina Center for Neurostimulation, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA; Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
Flavio FröhlichCarolina Center for Neurostimulation, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA; Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA; Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA; Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA; Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA. Electronic address: flavio_frohlich@med.unc.edu.
University of North Carolina at Chapel Hill · US

Funding

Rational Optimization of tACS for Targeting Thalamo-Cortical OscillationsR01MH111889 · NIMH · UNIV OF NORTH CAROLINA CHAPEL HILL · PI FROHLICH, FLAVIO · 2016 to 2019
$2.4M
Targeting Cortical Dynamics: Rational Design of Individualized Brain StimulationR01MH101547 · NIMH · UNIV OF NORTH CAROLINA CHAPEL HILL · PI FROHLICH, FLAVIO · 2013 to 2017
$2.2M
NIMH NIH HHS R01 MH101547NIMH NIH HHS R01 MH111889
6 · The paper itself

Abstract

backgroundSingle-pulse transcranial magnetic stimulation (TMS) elicits an evoked electroencephalography (EEG) potential (TMS-evoked potential, TEP), which is interpreted as direct evidence of cortical reactivity to TMS. Thus, combining TMS with EEG can be used to investigate the mechanism underlying brain network engagement in TMS treatment paradigms. However, controversy remains regarding whether TEP is a genuine marker of TMS-induced cortical reactivity or if it is confounded by responses to peripheral somatosensory and auditory inputs. Resolving this controversy is of great significance for the field and will validate TMS as a tool to probe networks of interest in cognitive and clinical neuroscience.

objectiveHere, we delineated the cortical origin of TEP by spatially and temporally localizing successive TEP components, and modulating them with transcranial direct current stimulation (tDCS) to investigate cortical reactivity elicited by single-pulse TMS and its causal relationship with cortical excitability.

methodsWe recruited 18 healthy participants in a double-blind, cross-over, sham-controlled design. We collected motor-evoked potentials (MEPs) and TEPs elicited by suprathreshold single-pulse TMS targeting the left primary motor cortex (M1). To causally test cortical and corticospinal excitability, we applied tDCS to the left M1.

resultsWe found that the earliest TEP component (P25) was localized to the left M1. The following TEP components (N45 and P60) were largely localized to the primary somatosensory cortex, which may reflect afferent input by hand-muscle twitches. The later TEP components (N100, P180, and N280) were largely localized to the auditory cortex. As hypothesized, tDCS selectively modulated cortical and corticospinal excitability by modulating the pre-stimulus mu-rhythm oscillatory power.

conclusionTogether, our findings provide causal evidence that the early TEP components reflect cortical reactivity to TMS.

Indexed as

Motor CortexTranscranial Direct Current StimulationBrainElectroencephalographyEvoked Potentials, MotorHumansMaleTranscranial Magnetic StimulationCortical reactivityElectroencephalographyMotor cortex excitabilitySource localizationTranscranial direct current stimulationTranscranial magnetic stimulation

Identifiers

PMID33516859
PMCPMC7987756
OpenAlexW3128185272

What OpenQuestion holds

Textmetadata
LicenceTDM
Read underepoch 390

Registered trials

None linked

Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.