Search

The aim of this study was to explore the role of expectancies and beliefs about the potential effects of electromagnetic fields (EMFs) (what the subject thought the effect was going to be) and the effects of 50 Hz magnetic fields (400 microT(rms)) acute exposure on cognitive performance, the reporting of physical symptoms and some psychological and physiological parameters. Seventy-four healthy male volunteers aged between 40 and 60 years of age were randomly assigned to one of five groups, which differed in (1) the type of information they were given concerning the expected magnetic field effect on performance in cognitive tests (positive = enhancement of the performance; negative = impairment of the performance; neutral) and (2) the type of exposure (real or sham). Three groups were sham exposed with positive (group+), negative (group-) and neutral information (group+/-); one group was really exposed with neutral information (group expo) and one group was not exposed, though they wore the helmet, and did not receive any field-related information (control group). All the volunteers, except the control group, were led to believe that they would be exposed to a magnetic field of 400 microT(rms). The experimental design respected a double blind procedure and the experimental session involved three steps (pre-testing, exposure, and post-testing). Various measurements were taken, including cognitive performance, psychological parameters such as mood, vigilance, and reporting of symptoms. Physiological parameters such as blood pressure and pulse rate were also recorded. The information given did not significantly modify beliefs. No significant difference was found among the five groups depending on the type of information and the type of exposure in cognitive performance, psychological and physiological parameters. In the context of the study, with our population, the type of information given failed to induce expected changes in parameters measured. Our results do not support the hypothesis that an acute exposure to extremely low frequency magnetic fields (50 Hz, 400 microT(rms)) affects the parameters measured.

The purpose of this study was to reproduce and extend two earlier studies of the effects of human exposure to 50 Hz magnetic fields (MF). In a recent paper, we described results of two double-blind investigations performed to examine effects of 100 microT(rms) 50 Hz MF exposure on psychological parameters in the same group of healthy human volunteers. In each exposure session, at 1 week intervals, with sham, continuous, and intermittent (15 s ON/OFF cycles) MF conditions, mood ratings, performance measures, and electrophysiological measures were taken. In the first study, significant amplitude changes were observed in the event-related brain potentials (ERP) recorded during a dichotic listening task. In the second study, latency and reaction time (RT) slowing were seen on a visual discrimination task (P(300) paradigm). Although these results were little related to the number of parameters analysed, they indicate that low level 50 Hz MF might have a slight influence on ERP and RT under specific circumstances of sustained attention. Before concluding that moderately strong MF exposure can influence cognitive function, previous results should be replicated, using the same paradigms with another group of healthy volunteers. In the present study, 18 healthy subjects were exposed to three experimental sessions of 30 min each, given at 1 week intervals. The sessions consisted of continuous 100 microT(rms) 50 Hz MF exposure, sham condition, and bright light (5000 lux) exposure. The study was performed double-blind, with the exposure order counter-balanced. The data on mood, ERP, RT, and other performance measures did not show any differences among the sham exposure, light exposure, and MF exposure conditions. The results of this study do not support the hypothesis that extremely low frequency (ELF) MF exposure affects the brain's electrical activity or cognitive function at field strength (100 microT(rms)) similar to that found in very close proximity of some household and industrial electrical appliances and well in excess of the average MF strength (c. 0.1 microT) found in homes. The sensitivity of the experiment was possibly not sufficient to detect an effect at this relatively low MF, and larger sample sizes would be required in further studies.

The aim of the present study was to investigate cognitive effects of a continuous, vertical extremely low frequency (ELF) magnetic field (MF) of 20 and 400 microT 50 Hz in healthy young men during performance on cognitive tests. Thirty-two volunteers (20-30 years old, mean 22.6 +/- 2.2 years) participated in this double blind study. The test protocol consisted of a set of tests: divided attention, flexibility, memory updating, digit span, digit span with articulary suppression, and time perception. The total duration of the exposure was 65 min. Participants were assigned four sessions: three conditions in the helmet (sham exposure, 20 and 400 microT) and one condition out of the helmet (to control the expectancy effect). No effect of MF exposure was observed on performance., (2004 Wiley-Liss, Inc.)

In this study, serum melatonin and urinary 6-sulfatoxymelatonin (aMT6s) were measured in 14 major depressive inpatients, compared to 14 matched controls according to age, gender, season and hormonal treatment in women. Moreover, the relationship between serum melatonin and urinary aMT6s levels was analysed in the two groups. Results indicated that the two groups of subjects showed a clear melatonin rhythm without significant difference in the mean level of melatonin or aMT6s, in the area under the curve of melatonin or in the melatonin peak. However, the time of the nocturnal melatonin peak secretion was significantly delayed in depressive subjects as compared to healthy controls. Moreover, the depressed patients showed urinary aMT6s concentrations enhanced in the morning compared to night time levels, while these concentrations were lowered from the night to the morning in the control group. These results suggest that the melatonin production is phase-shifted in major depression.

This paper reviews the effect of 50-60 Hz weak electric, magnetic and combined electric and magnetic field exposure on cognitive functions such as memory, attention, information processing and time perception, as determined by electroencephalographic methods and performance measures. Overall, laboratory studies that have investigated the acute effects of power frequency fields on cognitive functioning in humans are heterogeneous, in terms of both electric and magnetic field (EMF) exposure and the experimental design and measures used. Results are inconsistent and difficult to interpret with regard to functional relevance for possible health risks. Statistically significant differences between field and control exposure, when they are found, are small, subtle, transitory, without any clear dose-response relationship and difficult to reproduce. The human performance or event related potentials (ERPs) measures that might specifically be affected by EMF exposure, as well as a possible cerebral structure or function that could be more sensitive to EMF, cannot be better determined.

A radioimmunoassay of urinary 6-sulphatoxymelatonin (a-MT6s) was performed in 90 normal subjects: 44 males and 46 females (17-67 years). Patients treated with betablokers or antidepressants were not included in this study. Urine samples were collected over three periods of time: 7 to 11 p.m., 11 p.m. to 7 a.m., and 7 to 11 a.m. Between 11 p.m. and 7 a.m., the subjects slept in their normal environment and had not ingested alcohol for 24 hours. We searched for a possible relation between urinary a-MT6s excretion (expressed in ng/l/h) and age. From 7 to 11 p.m. and from 7 to 11 a.m. no significant relation could be found. On the contrary, between 11 p.m. and 7 a.m. there was a significant relation indicating decrease of a-MT6s secretion with increasing age. Several linear or non-linear curve patters were tested: Boltzmann sigmoid (1(st), 2(nd), and 3(rd) degree), polynomial curves. The Boltzmann sigmoid showed the best fit judging by the r-squared value (0.152) and the runs test (p=0.64). On this curve the inflection point was located at 53 4 years (SDM, standard deviation of the mean). From 19 to 45 years, the upper sigmoid plateau was located at 1381 91 ng/l/h (SDM). The decrease was found between 45 and 60 years and the lower sigmoid plateau then stabilized at 467 370 ng/l/h (\SDM). In the study group, there was no significant difference between men and women according to the Mann-Withney test. Finally, use of oral contraceptives did not affect urinary a-MT6s (Mann-Withney).

Concern about the health effects of extremely low frequency (ELF) magnetic fields (MF) has been raised by epidemiological studies indicating an association between certain cancers and living near power lines or working in high electric field environments. Alterations in pineal function have been proposed as a mechanism through which power-frequency MFs may interact with living organisms. A double blind laboratory study was performed to evaluate daytime exposure effects of 100 microT root mean square (rms) 50 Hz MF. Three head exposure sessions of 30 min each were performed: sham, continuous, and intermittent (15 s on/off cycles) MFs were presented to each subject in early or late afternoon (13:30 or 16:30 hr). Twenty-one healthy male volunteers (20-27 yr old) participated in these 3-weekly experimental conditions. Blood samples were drawn for serum melatonin measurement, hourly at night (from 20:00 to 07:00 hr) under controlled environmental conditions. Urinary excretion of 6-sulfatoxymelatonin (aMT6s), the main melatonin metabolite, was measured for a 17 hr period, by means of urine samples taken at 19:00 hr (14:00-19:00 hr "afternoon period"), 23:00 hr (19:00-23:00 hr "evening period"), and 07:00 hr, day 2 (23:00-07:00 hr day 2 "night-time period"). There were no significant differences in either plasma melatonin or in aMT6s excretion profiles in the three experimental conditions. However, a tendency for a smaller increase of night-time urinary aMT6s after continuous MF exposure was found (P=0.08) particularly in men with the lower excretion rate of aMT6s ("Low Group") (P=0.07). We conclude that this study does not indicate that daytime acute MF exposure influences either melatonin secretion or aMT6s excretion. Inter-individual differences in pineal production of melatonin, however, have to be taken into account in further studies.

The use of CNV in clinical practice requires the choice of a standardised protocol, the constitution of reference normative data and the consideration of intra- and interindividual variability. For this purpose, we recorded CNV in 86 control subjects (44 men and 42 women, 18 to 62 years old (mean age = 34 +/- 13 years) during a reaction time paradigm with a warning signal and a 1-second S1-S2 interval. Moreover, the role of inter-stimulation interval was analysed in a group of 12 subjects through the comparison of recordings made with 1- and 3-second intervals. The CNV amplitude, its morphology and topographic distribution as well as its resolution mode and evolution through the recording were studied. The subjects' performances and their interactions with electroencephalographic data were also included in the analyses. Our results underscore the contribution of age and gender and psychological factors to CNV variability. CNV amplitude (both M1 and M2) increased and changed topographic distribution toward more central sites in older. Men had faster reaction times than women and lower post-S1 P300. Moreover, the life events-related stress and the subject's current anxiety level were accompanied by a decreased CNV amplitude.

Melatonin is a hormone mainly secreted by the pineal gland during the dark phase of the light-dark cycle. The most known function of melatonin in mammals is to transmit information concerning light-dark cycles playing the role of an active neuroendocrine transducer of environmental information. Given this chronobiologic role of pineal melatonin, it seems to be useful in the management of shift work, jet lag and some sleep disorders. In vitro like in vivo melatonin seems to be effective as an antioxidant and oncostatic agent. Melatonin may provide protection against aging process, degenerative diseases, cancer and play a role also in sexual maturation, reproduction, immune function and psychiatric illness. The administration of melatonin in the jet-lag syndrome is well codified. Further clinical research is needed for a better understanding and definition of other indications, treatment regimens and safety of the hormone. The aim of this paper is to review the current knowledge on its clinical implications.

Melatonin is a hormone mainly secreted by the pineal gland during the dark phase of the light-dark cycle. The best known function of melatonin in mammals is to transmit information concerning light-dark cycles playing the role of an active neuroendocrine transducer of environmental information. Although melatonin circadian rhythm is endogenous, based on 25 hour cycles, it is modulated by light-dark cycle. During the day, the light signal is sent to the pineal gland through a special neuronal pathway and inhibits melatonin secretion. During the night, the last neuron of this pathway which is coming from the cervical ganglion superior releases nonadrenalin in the interstitium. Nonadrenalin stimulates melatonin synthesis through cAMP accumulation. Some factors other than light can also influence melatonin levels. Electromagnetic fields, age, male sex, Cushing syndrome, hypogonadotrophic hypogonadism, alcoholism seem to be associated with lower melatonin secretion. Female sex, hypergonadotrophic hypogonadism, sport and fasting seem to be linked to higher melatonin secretion. Some pathologies and drugs can modulate some steps of the neuroanatomic pathway of melatonin synthesis. Stress has no effect. The influence of weight and height is still investigated. Once released, melatonin can act on different organs through specific receptors (retina, supra-chiasmatic nucleus, hypophysis, brain, blood vessels, digestive tract, ovaries).

Two double-blind studies were performed to examine magnetic field (MF) exposure effects and to determine the impact of temporal variation (continuous vs. intermittent exposure) of 100 mu T(rms) 50 Hz MF diurnal exposure on psychological and psychophysiological parameters in healthy humans. Three cephalic 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 1-wk intervals. In each session, mood ratings and performance measures were obtained before, during, or after exposure and several electrophysiological data (event-related brain potentials [ERP]) were recorded after each exposure session. These criteria were chosen to evaluate sensory functions as well as automatic and voluntary attentional processes. In experiment 1, 21 healthy male volunteers (20 to 27 years of age) were studied. Ten subjects were exposed at 13:30 h, and 11 subjects were exposed at 16:30 h. Statistically significant changes in the amplitude of ERP were observed after MF exposure in the dichotic listening task, indexing selective attention processes. Eighteen of the 21 original male volunteers took part in experiment 2, undertaken to better understand the results 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 changes of the ERP recorded in the dichotic listening task. Moreover, they demonstrated ERP latency and reaction time slowing in the oddball paradigm, a visual discrimination task after real MF exposure. These results also indicate that a low level 50 Hz MF may have a slight influence on event-related potentials and reaction time under specific circumstances of sustained attention., (Copyright 1999 Wiley-Liss, Inc.)

The use of P300 in psychopathology raises the important problem of the constitution of reference normative data and of the high variability of auditive ERP's in controls. To handle better this problem, we recorded 86 control subjects, using an auditory oddball paradigm with motor response. We analyzed the successive components of the ERP's evoked by target and standard stimuli (N1, P2, N2, P3a, P3b and slow wave negativity). Our results underlined the role of age, sex and psychological factors on the ERP's interindividual variability: P3 amplitude decreased and its latency increased with age, while its topography was more frontal in the older than in the younger subjects. The P300 occurrence after standard stimuli and P3 amplitude after target stimuli were different according to sex. Moreover, P300 amplitude, latency and topography were related to the subject's anxiety level. Finally, our results also propose new description modes of ERP's relying on P3a and P3b relative peak amplitude (P300 with prominent P3a or P3b), topographical predominance (frontal or parietal P300) and duration of the late positive complex (brief or long-lasting P300). These data will improve the clinical use of P300.