Electrode placement in transcranial direct current stimulation—how reliable is the determination of C3/C4?

Tonya L. Rich, Bernadette T. Gillick

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


The 10/20 electroencephalogram (EEG) measurements system often guides electrode placement for transcranial direct current stimulation (tDCS), a form of non-invasive brain stimulation. One targeted region of the brain is the primary motor cortex (M1) for motor recovery after stroke, among other clinical indications. M1 is identified by C3 and C4 of the 10/20 EEG system yet the reliability of 10/20 EEG measurements by novice research raters is unknown. We investigated the reliability of the 10/20 EEG measurements for C3 and C4 in 25 adult participants. Two novice raters were assessed for inter-rater reliability. Both raters received two hours of instruction from a registered neurodiagnostic technician. One of the raters completed the measurements across two testing days for intra-rater reliability. Relative reliability was determined using the intraclass coefficient (ICC) and absolute reliability. We observed a low to fair inter and intra-rater ICC for motor cortex measurements. The absolute reliability was <1.0 cm by different novice raters and on different days. Although a low error was observed, consideration of the integrity of the targeted region of the brain is critical when designing tDCS interventions in clinical populations who may have compromised brain structure, due to a lesion or altered anatomy.

Original languageEnglish (US)
Article number69
JournalBrain Sciences
Issue number3
StatePublished - Mar 2019

Bibliographical note

Funding Information:
Funding: This work was supported by NIH (5K01HD078484-03, PI: Gillick), Foundation for Physical Therapy, Cerebral Palsy Foundation, Minnesota’s Discovery, Research, and Innovation Economy (MnDRIVE) Fellowship, and University of Minnesota Marie Louise Wales Fellowship.

Publisher Copyright:
© 2019, MDPI AG. All rights reserved.


  • Adults
  • Children
  • Electroencephalogram
  • Neuroplasticity
  • Non-invasive brain stimulation
  • Stroke
  • Transcranial direct current stimulation


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