Group level magnetoencephalography source power for highest administered xenon and nitrous oxide concentrations. Xenon (Xe) effects (A) at loss of responsiveness (1.30 MAC_awake) are increases in low-frequency delta (widespread change) and theta activity (right brain lateralized). 0.75 MAC_awake nitrous oxide (N₂O) (B) results in a primarily frontal alpha reduction and a rise in high-frequency gamma activity centered around frontal and occipital regions. Maximum statistics and Bonferroni corrected t-maps ([top row] Xe, P = 0.004; N₂O, P = 0.005) of magnetoencephalographic sources across participants (n = 21). Brain slices (middle row) display region specific alterations plotted on the template Montreal Neurological Institute and Hospital (MNI) brain. Magnetoencephalography source spectral power ([bottom row] 1 to 45 Hz) is shown in the logarithmic scale for the postantiemetic baseline and the highest administered doses of the two gases averaged across all magnetoencephalographic sources and all subjects. Delta, 1 to 4 Hz; theta, 4 to 8 Hz; alpha, 8 to 13 Hz; low gamma, 30 to 49 Hz; high gamma, 51 to 99 Hz. MAC_awake, minimum alveolar concentration–awake.