Does phase-modulation of applied 40-Hz transcerebral magnetic fields affect subjective experiences and hypnotic...

12 men and 12 women were exposed to a sham-field, a 5-Hz sine-wave magnetic field, a 40-Hz sine-wave magnetic field, or the latter field-phase modulated five times per sec. (5-Hz) for 30 min. between two administrations of the Spiegel's Hypnotic Induction Profile. To replicate the geometry that has produced significant increases in these scores in previous studies, the weak (1 microT) magnetic fields were applied over the right parietotemporal region through a modified helmet. The hypothesis that the enhanced suggestibility previously observed was due to an intrinsic phase-modulation of the fields was not supported. However, the ratings of overall pleasantness of the experiences were negatively correlated (r = -.36) with global geomagnetic activity at the time of the experiment. The pleasantness was ranked significantly greater by subjects exposed to the 40-Hz field (explaining 41% of the variance) relative to subjects exposed to the 5-Hz field who also reported more visual experiences within their left peripheral visual fields. The percentages of time alpha rhythms were measured over the temporal lobes (but not frontal or occipital lobes) during the treatments were moderately and positively correlated with scores on questionnaires administered before the experiment, from which the capacity to imagine, temporal lobe signs, and religious (but not exotic) beliefs were inferred. The groups exposed to either the 5-Hz or 40-Hz/5-Hz phase-modulated field displayed greater durations of alpha rhythms over the temporal lobes than the other two groups.