EEG data were recorded under field conditions from 11 members of the Santo Daime Doctrine, a Brazilian shamanistic religion, before and after ingesting the psychoactive alkaloid preparation, ayahuasca, or daime, as they term it. Post-ingestion, we observed increases in power in the 36-44 Hz frequency band ("40 Hz") from the left occipital-temporal-parietal scalp electrodes in the eyes-closed...