Résumé
Magnetophosphenes are lightless visual percepts induced by exposure to extremely low-frequency magnetic fields (ELF-MF). Despite well-defined perception thresholds, electroencephalography (EEG) findings have been difficult to reproduce and focal low-frequency power changes have not provided a robust within-study marker of perceptual reports. We tested whether perception under 20 Hz global-head ELF-MF exposure is better captured by high-frequency spectral content of ongoing EEG activity. EEG was recorded in 14 healthy volunteers (13 retained after predefined quality control) during 5-s sinusoidal exposures at 0 mT (control), 5 mT (perceptual subthreshold), and 50 mT (perceptual suprathreshold), in darkness with eyes closed. Gamma-band activity (30–80 Hz) was quantified using Welch’s method. Electrode-wise effects were tested with trial-level linear mixed-effects models with Bonferroni correction across 64 channels. Perception sharply dissociated conditions (0 mT: 0/65 trials; 5 mT: 1/65; 50 mT: 57/65). At 50 mT, gamma-band power increased over frontal and occipital electrodes and remained detectable after aperiodic adjustment, without a consistent narrowband gamma peak. These results link suprathreshold magnetophosphene perception to broadband high-frequency changes rather than a single focal low-frequency marker.