Behavioral Effects


Most of the major paradigms used in behavioral research have been employed successfully to establish the existence of EMF-induced behavioral effects. These include studies of spontaneous activity, reaction time, and conditioned responses.

When motor activity was evaluated by tilt cages, traversal of open-field mazes, or other ambulatory behaviors, it was found that the responses depended on the characteristics of both the measuring system and the applied EMFs. Eakin and Thompson (30) used 320-920 MHz, 760 µW/cm2, for 47 days and found that the exposed rats were more active than the controls during the first 20 days of exposure, and less active thereafter. These results were confirmed and extended by Eakin in 1970 when hypoactivity was reported following prolonged exposure to 150-430 µW/cm2 (31). Roberti et al. (32) failed to find an effect due to 3 -10 GHz for 7 days at 1000 µW/cm2,but Mitchelletal. (33),who exposed rats to 2.45 GHz at about 600 µW/cm2 for 22 days (5 hr/day), found an EMF-induced hyperactivity in the exposed animals compared to both their pre-exposure baseline and the activity of sham-exposed controls. The field-induced activity changes in each of these studies were measured during periods when the animals were removed from the field. When activity was measured during exposure to a modulated 40-MHz electric field (34), it first increased, then decreased, during the 2-hour exposure period. This result supported an earlier finding by the same group that the field caused a similar pattern of change in the emotional response of rats as measured by the Olds self-stimulation response (35).

The pattem of a dual effect upon performance-stimulation or inhibition, depending on the circumstances-has not emerged at the low frequencies, most such studies having found only increased activity. At 1000 v/m, 60 Hz (5 days) (36), and 60,000 v/m, 50 Hz (3 hr) (37), the nocturnal activity of rodents was increased. An increase in activity in two strains of mice was also seen following exposure to 17 gauss at 60 Hz (38). Other spontaneous behaviors have been found to be susceptible to EMFs, including pain-induced aggression (I7), escape (75), avoidance (76-78) and sleep pattern (79).

A standard behavioral measure of a subject's ability to respond to changes in its environment is its reaction-time to a visual or auditory stimulus. In several studies this has been altered by low-frequency EMFs. According to Konig and Ankermuller (40), at 1 v/m, 10 Hz and 3 Hz are associated with a decrease and increase, respectively, in human reaction time as compared to the field-free situation. In an experimental design in which each subject was exposed to two frequencies in the 2-12 Hz range, at 4 v/m, Hamer found a longer reaction time at the higher frequency (41). Friedman et al. applied magnetic fields of 0.1 and 0.2 Hz to separate groups of male and female subjects, and for both groups he found a longer reaction time at the higher frequency compared to the lower frequency (42). Persinger et al. found no difference in the mean reaction time in either males or females due to 0.3-30 v/m, 3-10 Hz, but he did find a significant difference between the sexes in the variability of the response to a given field (43).

As measured by a task consisting of the addition of sets of five two-digit numbers, a 60 Hz, 1-gauss field altered the ability to concentrate in human subjects (Fig. 5.5) (39). All 6 experimental subjects demonstrated a decline in performance in the second test session of the exposure period, and all 6 improved in the first test session of the postexposure period. In contrast, the control subjects showed no consistent changes.


Fig. 5.5 Average performance of the experimental and control groups on the Wilkinson Adding Task. The subjects were confined to the test facility throughout the study, and were unaware of the exact timing of the 24-hour exposure period.


For more than a decade, Ross Adey and his colleagues have sought to understand the molecular mechanisms that underlie field-induced behavioral changes. In the late 1960's they reported that low-frequency EMFs altered the timing behavior in humans (41) and monkeys (50). The effects were frequency-dependent in the 2-12. Hz range, and later results suggested that they increased with dose (51). In 1973, they reported that cats exposed to 147-MHz EMFs, modulated at 0.5-30 Hz, exhibited altered EEGs (44). The idea that evolved from these studies and others (53), was that extremely weak EMFs-I0-5 v/m, as calculated on the basis of the simple spherical model described in chapter 2-could alter neuronal excitability, and presumably timing behavior and the EEG, if they were in the physiological frequency range (the EEG). An in vitro system involving calcium binding to brain tissue was then chosen to study the effect of weak EMFs on ionic movement under a hypothesis that altered ion-binding and the associated conformational changes constituted the mechanism of the EMF-induced effects. A complex series of results were then obtained concerning the levels of pre-incubated calcium that were released into solution: at 147 MHz, there was an increase when the EMF was modulated at 6- 10 Hz, but no increase at 0.5-3 or 25-35 Hz (65 ); with EMFs of 6 and 16 Hz, there was a decrease at 10 and 56 v/m, but not at 5 or 100 v/m (66); there was no change in calcium at 1 Hz or 32 Hz, at either 10 or 56 v/m (66); at 450 MHz, modulated at 16 Hz, there was an increase (67). Some of these results have been confirmed (71). The salient features of the in vitro studies were: (1) the emphasis on calcium; (2) the opposite results obtained following low-frequency and high-frequency EMF exposure; and (3) the existence of frequency and field-strength ranges where the effects were at a maximum. None of these features were seen in the in vivo studies. Grodsky proposed a cell-membrane model involving cooperative charge interactions as a partial explanation of Adey's results (80), but their molecular basis still remains speculative (52).

There have been reports of the effects of EMFs on conditioned responses in both operant (44-51, 74) and respondent paradigms (8, 54-58). In the operant studies, the effect of the EMFs was usually established on the basis of changes in discrete movement by the test subjects. For example, Thomas (74) found that a pulsed EMF of 1000 µW/cm2, 2.45 GHz, altered the effect of chlordiazepoxide on behavior. The drug produced a change in the bar-pressing rate which was potentiated in the presence of the EMF. In the respondent studies, typically, the field-induced effects were more generalized and consisted of responses such as impaired endurance (57). The use of EMFs as conditioned stimuli during periods preceding aversive stimuli has frequently (59-61), but not always (62-64), failed.

Chapter 5 Index