Deficits in spatial learning after exposure of mice to a 50 Hz magnetic field

Abstract

A series of four experiments was performed to determine the effect of exposure to a 50 Hz magnetic field on memory‐related behaviour of adult, male C57BL/6J mice. Experimental subjects were exposed to a vertical, sinusoidal magnetic field at 0.75 mT (rms), for 45 min immediately before daily testing sessions on a spatial learning task in an eight‐arm radial maze. Control subjects were only exposed to a background time‐varying field of less than 50 nT and the ambient static field of about 40 μT. In each experiment, exposure significantly reduced the rate of acquisition of the task but did not affect overall accuracy. This finding is consistent with the results of another study that found that prior exposure to 60 Hz magnetic fields affected spatial learning in rats. Bioelectromagnetics 19:79–84, 1998. © 1998 Wiley‐Liss, Inc.

Chronic exposure to low-intensity magnetic field improves acquisition and maintenance of memory

“…Over decades of studies, problems concerning the biological effects of ELF MF are still controversial and inconsistent. Accumulating evidence suggests that ELF MF exerts influence on the process of learning and memory in both animals [1] and human beings [2].…”

“…For example, Lai [3] reported that exposure to 1 mT, 60-Hz magnetic field (MF) for 1 h immediately before each training session of the Morris water maze test impaired the spatial memory retention. Likewise, in radial maze test, exposure to 0.45 mT ELF MF for 45 min shortly before daily testing sessions reduced the acquisition rate of spatial learning task [1]. More recently, it was found that 20-min exposure to 8 mT MF after training sessions impaired the consolidation of spatial memory [4].…”

Single, brief exposure to a 50 Hz magnetic field does not affect the performance of an object recognition task in adult mice

“…In these studies using rats and mice, animals who had been exposed at 0.75 mT for 45 min before testing made signi®cantly more errors in a radial arm maze than control animals during performance of a food-reinforced task [Lai, 1996;Sienkiewicz et al, 1998aSienkiewicz et al, , 1998b although in the case of the mice at least, overall accuracy was not impaired, and the ®nal levels of performance were comparable to the control animals [Sienkiewicz et al, 1998a]. Further evidence for an effect of magnetic ®elds on spatial memory comes from a recent study using a Morris water maze [Lai et al, 1998].…”

“…There is growing evidence to suggest that the processing of spatial information in adult animals can be affected by exposure to speci®c combinations of static and time-varying ®elds at about 50 mT [Creim et al, 1990;Lovely et al, 1991Lovely et al, , 1992Lovely et al, , 1993Lovely et al, , 1994Cheryshev et al, 1997], and by exposure to power frequency ®elds at 100 mT [Kavaliers et al, 1993[Kavaliers et al, , 1996Lai, 1996;Lai et al, 1998;Sienkiewicz et al, 1998aSienkiewicz et al, , 1998b. Both increases and decreases in learning pro®ciency have been reported, although some studies have failed to ®nd any signi®cant ®eld-dependent effects Sienkiewicz et al,1996].…”

Study of high-frequency electromagnetic field effect on some somatic and neuro-behavioral characteristics in healthy and neurodefective mice

“…Recently, rats exposed also for 2 h to GSM MWs (915 MHz, SAR 0.4 mW/g) exhibited affected expression of genes in cerebellar cells (Belyaev et al 2006). Behavioral experiments in animals showed performance deficits in spatial learning in rats (Lai et al 1998) and in mice (Sienkiewicz et al 1998) exposed to low-frequency EMF (50 and 60 Hz). Affected learning process was also described in rats exposed to HF EMF (2,450 Hz) and examined in the radial and the Morris water maze (Lai et al 1994;Wang and Lai 2000).…”