Test-retest reliability of transcranial magnetic stimulation EEG evoked potentials

Background

Transcranial magnetic stimulation (TMS)-evoked potentials (TEPs), recorded using electroencephalography (TMS-EEG), offer a powerful tool for measuring causal interactions in the human brain. However, the test-retest reliability of TEPs, critical to their use in clinical biomarker and interventional studies, remains poorly understood.

Objective/Hypothesis

We quantified TEP reliability to: (i) determine the minimal TEP amplitude change which significantly exceeds that associated with simply re-testing, (ii) locate the most reliable scalp regions of interest (ROIs) and TEP peaks, and (iii) determine the minimal number of TEP pulses for achieving reliability.

Methods

TEPs resulting from stimulation of the left dorsolateral prefrontal cortex were collected on two separate days in sixteen healthy participants. TEP peak amplitudes were compared between alternating trials, split-halves of the same run, two runs five minutes apart and two runs on separate days. Reliability was quantified using concordance correlation coefficient (CCC) and smallest detectable change (SDC).

Results

Substantial concordance was achieved in prefrontal electrodes at 40 and 60?ms, centroparietal and left parietal ROIs at 100?ms, and central electrodes at 200?ms. Minimum SDC was found in the same regions and peaks, particularly for the peaks at 100 and 200?ms. CCC, but not SDC, reached optimal values by 60–100 pulses per run with saturation beyond this number, while SDC continued to improve with increased pulse numbers.

Conclusion

TEPs were robust and reliable, requiring a relatively small number of trials to achieve stability, and are thus well suited as outcomes in clinical biomarker or interventional studies.