[Biphasic response of the human nervous system to geomagnetic storms studied by EEG]

In two subjects: a male phlegmatic, 56, and a female melancholic, 22, the EEG was recorded at resting. The EEG patterns were juxtaposed with the geomagnetic activity index Ar and the solar activity index SF, as well as between themselves. The results revealed qualitatively similar biphasic responses: a generalised diminishing of the EEG spatial synchronisation and, on the next day, a generalised augmentation of the phenomenon, as compared with a prolonged quiet period. A general unspecific stress response is supposed to underlie the aforementioned dynamics, whereas a reduced cortical tone during a magnetic storm and an enhanced one after its cessation correspond to the two phases observed. Specifics of responses in both subjects corresponded to their individual profiles of interhemisphere asymmetry.