Geophysical variables and behavior: XCI. Ambulatory behavior in rats following prenatal exposures to complex magnetic fields designed to interact with genetic expression

Conspicuous Histomorphological Anomalies in the Hippocampal Formation of Rats Exposed Prenatally to a Complex Sequenced Magnetic Field within the Nanotesla Range

The brains of adult rats, exposed prenatally to one of four intensities (between 10 nanoTesla and 1.2 microTesla) of either a frequency-modulated magnetic field or a complex sequenced field designed to affect brain development, were examined histologically. Although from each intensity some rats that had been exposed to the complex sequenced magnetic field showed minor anomalies, those exposed to intensities between 30 nT and 180 nT exhibited conspicuous anomalous organizations of cells within the hippocampal formation. In other studies, rats that had been exposed during their entire prenatal development to the complex sequenced field displayed significantly more activity in the open field and poorer spatial memory during maze learning. Photomicrographs are shown of one conspicuous morphological anomaly within the right hippocampus of an adult rat exposed prenatally to the complex sequenced magnetic field with intensities between .3 mG and .5 mG (30 nT to 50 nT). The results suggest that complex magnetic fields, whose temporal structures approach the time constants of normal biochemical processes, can permanently alter the development of the brain.

COMPLEX MAGNETIC FIELDS ENABLE STATIC MAGNETIC FIELD CUE USE FOR RATS IN RADIAL MAZE TASKS

Male Wistar rats were trained in an eight-arm radial maze task (two sessions per day, delayed-non-matching-to-sample) that included an intramaze static magnetic field "cue" (185 microT) specific to the entrance point of one of the arms. Rats were exposed daily for 60 min to a complex magnetic field waveform (theta-burst pattern, 200-500 nT), presented with several different interstimulus intervals (ISIs), either immediately following training sessions or immediately preceding testing sessions. Application of the theta-burst stimulus with a 4000 ms ISI significantly improved the rats' memory for the arm of the radial maze whose position was indicated by the presence of a static magnetic field cue. Reference memory errors were homogeneously distributed among all eight arms of the maze for sham-exposed rats, and among the other seven arms of the maze for complex magnetic field-treated rats. These results suggest that static magnetic field cues may be salient orienting cues even in a microenvironment such as a radial maze, but their use as a cue during maze learning in rats is dependent on whole-body application of a specific time-varying complex magnetic field.

Radial maze proficiency of adult Wistar rats given prenatal complex magnetic field treatments

Exposure to sinusoidal (power-frequency) magnetic fields during prenatal development is implicated in adulthood behavioral impairments. However, the effects of prenatal exposure to weak-intensity, nonsinusoidal complex magnetic fields (CMFs), an increasingly common feature of the modern environment, have not been rigorously examined. In the present study, male and female Wistar-strain rats were exposed continually during prenatal development to one of three extremely low-frequency CMFs or a sham condition. As adults, rats were trained in an acquisition/reversal radial maze task. All rats exposed to the prenatal CMFs increased their commission of reference memory errors, but differences in working memory and motivation to complete the maze task were specific to the type of prenatal CMF. These results provide the first evidence that prenatal exposures to specific shapes of CMFs impair complex learning behaviors into adulthood.

Geophysical variables and behavior: XCVII. Increased proportions of the left-sided sense of presence induced experimentally by right hemispheric application of specific (frequency-modulated) complex magnetic fields

12 young men and women who were not aware of the stimulus order were exposed to 8 configurations of weak 1 microTesla) magnetic fields for 5 min. each, applied primarily over the right parietotemporal region. The numbers of sensed presences along the left side, right side, or front/back, as inferred by button presses at the time of the experience, were recorded. There were significantly (eta2= .37) more experiences along the left side than the right side during the presentations of a frequency-modulated (Thomas) pattern with 3-msec. point durations compared to the presentation of its temporally reversed structure or to patterns that were more or less complex. 40% of all left-sided presences occurred during the 5-min. presentation of this specific frequency-modulated pattern. These results suggest that the subjective lateralization of a sensed presence to the left during right hemispheric stimulation by weak magnetic fields is enhanced by the specific temporal structure of the applied field.