BCIwiki (bciwiki.com) — A collaboration involving the University of Geneva, Switzerland, and the CIBM Center for Biomedical Imaging posted a preprint to bioRxiv on September 27, 2026. It tested whether wetting hair directly with tap water could improve dry-electrode EEG signal quality. The preprint has not been peer reviewed. The study recruited 22 healthy participants and compared resting-state EEG under dry, semi-dry, and gel conditions within a single session.
The researchers analyzed electrode impedance, spectral power, and functional connectivity. Relative to the dry condition, hair-wetting improved mean electrode impedance by 75.7% and reduced the proportion of bad channels from approximately 40% to 15%. Spectral-power similarity with gel recordings increased by 7.7% during eyes-closed recordings, while functional-connectivity similarity with gel recordings improved by approximately 56–70% across frequency bands. Spectral power describes signal strength at different frequencies; functional connectivity measures statistical associations between signals.
The authors interpret hair-wetting as a possible compromise for improving EEG data quality under suboptimal recording conditions, although it did not fully match the signal quality of traditional gel systems. The observations concern resting-state EEG in healthy participants and do not establish improved brain-computer interface (BCI) task performance or clinical efficacy.