50 hz magnetic field exposure influence on human performance and psychophysiological parameters: Two double-blind experimental studies

Two double-blind studies were performed to examine magnetic field (MF) expo sure effects and to determine the impact of temporal variation (continuous vs, intermittent exposure) of 100 mu T-rms 50Hz MF diurnal exposure on psyc hological and psychophysiological parameters in healthy humans. Three cepha lic exposure sessions of 30-min, i.e., sham, continuous, and intermittent ( 15 s ON/OFF cycles) MF conditions, were involved. Each subject participated in all sessions, which were spaced at l-wk intervals. In each session, moo d ratings and performance measures were obtained before, during, or after e xposure and several electrophysiological data (event-related brain potentia ls [ERP]) were recorded after each exposure session. These criteria were ch osen to evaluate sensory functions as well as automatic and voluntary atten tional processes. In experiment 1, 21 healthy male volunteers (20 to 27 yea rs of age) were studied. Ten subjects were exposed at 13:30 h, and 11 subje cts were exposed at 16:30 h. Statistically significant changes in the ampli tude of ERP were observed after MF exposure in the dichotic listening task, indexing selective attention processes. Eighteen of the 21 original male v olunteers took part in experiment 2, undertaken to better understand the re sults related to information processing involved in selective attention and control for ultradian rhythmicity. Exposure time for all the subjects was at 13:30 h. The analysis of the data again revealed significant amplitude c hanges of the ERP recorded in the dichotic listening task. Moreover, they d emonstrated ERP latency and reaction time slowing in the oddball paradigm, a visual discrimination task after real MF exposure. These results also ind icate that a low level 50 Hz MF may have a slight influence on event-relate d potentials and reaction time under specific circumstances of sustained at tention. (C) 1999 Wiley-Liss, Inc.