Test-retest reliability in electroencephalographic recordings

The electroencephalography is a technique used in brain mapping with applications in research and clinical practice. The current work aims to assess the reliability of quantitative electroencephalography and coherence measurements. Two electroencephalography sessions, obtained 4 to 6 weeks apart during resting state and memory condition, were recorded in 15 young healthy subject. For each subject power spectrum and coherence were calculated in six frequency bands: delta, 1-4 Hz; theta, 4-8Hz; alpha1, 8-10Hz; alpha2, 10-13Hz; beta, 13-30Hz; and gamma, 30-50Hz. Measurements were averaged into 8 regions of interest trying to cover different brain regions. The reliability of each measure for frequency band and ROI was calculated using the intraclass correlation coefficient (ICC). Significant reliability was obtained for qEEG (ICC = 0.74 in resting recordings and ICC = 0.66 in memory recordings, p<;0.006 corrected for multiple comparison) but not for coherence. These results suggest that qEEG metrics are sufficiently reliable to be considered in longitudinal studies.