Geophysical variables and behavior: XXV. Alterations in memory for a narrative following application of theta...

Subjects were asked to listen to a 3-min. narrative. During Min. 1, 2, or 3 of the narrative, subjects were exposed for 60 sec. to either 5-Hz or 20-Hz electromagnetic fields or to a sham field condition. The fields were generated by commercial devices and applied externally to the side of the head at the level of the temporal lobe. The transcript of each subject's version of the narrative was evaluated by discourse analyses for the numbers of direct recalls or of inferences for each of the three segments. Subjects who had received the 5-Hz fields during Min. 1 and 2 of the narrative displayed twice as many inferences for the material that had been presented during Min. 1 only compared to the 20-Hz groups who did not differ from the sham-field subjects. We hypothesize that there are small alterations in the processing of complex series of verbal stimuli by these weak, theta frequency electromagnetic fields. They might not affect the amount of recall but they may influence the details of recall.