Brief exposure to 60 Hz magnetic fields improves sexually dimorphic spatial learning performance in the meadow vole, Microtus pennsylvanicus

Abstract

1. This study examined spatial learning and memory in breeding adult male and female meadow voles, Microtus pennsylvanicus, and the effects of brief exposure to weak (0.1 mT or 1.0 Gauss rms) 60 Hz magnetic fields on their spatial performance.2. There were significant sex differences in the spatial performance of the polygynous meadow voles. Reproductive male voles displayed significantly better spatial learning and retention than reproductive females in a Morris water maze task, whereby individual voles had to learn and remember the location of a submerged hidden platform using extramaze visual cues. Males showed over 9 days of daily blocks of 4 trials both a faster rate and greater overall level of acquisition (shorter latency to find hidden platform) of the spatial task than did the females.3. Brief (maximum 5 min) exposure to 60 Hz magnetic fields during acquisition of the water maze task significantly enhanced the spatial performance of both the male and female meadow voles. Females showed a relatively greater facilitation of spatial acquisition and retention than did the males, resulting by day 9 in the elimination of sex differences in water maze performance. 4. The time-varying magnetic fields may be: (i) functioning as orientation cues and providing directional cues, and/or (ii) affecting neuromodulatory systems that are involved in the mediation of spatial learning and memory. Exposure to weak time-varying magnetic fields has been shown to attenuate the activity of endogenous opioid systems, enhance protein kinase C (PKC) activity, and alter calcium ion flux. These effects have been shown to affect spatial learning and memory and are consistent with an enhancement of water maze performance.

Long‐term Exposure to Extremely Low‐frequency Magnetic Fields Impairs Spatial Recognition Memory in Mice

“…However, some studies have shown that acute exposure to 50 Hz fields has no effect on spatial learning in the radial arm maze in mice 10 . Moreover, other studies have demonstrated that brief exposure to weak 60 Hz fields enhances spatial learning performance in the water maze in both meadow voles 11 and deer mice 12 . These differences in outcome may depend on experimental variables, such as behavioural tasks, field strength and exposure conditions.…”

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

“…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].…”

Investigations of a simulated geomagnetic field experienced by the international space station on attentional performance

“…In fact, in the literature there are some reports that EMF exposure can modify spatial memory and place learning in animals [Kavaliers et al, 1993[Kavaliers et al, , 1996Lai, 1996;Sienkiewicz et al, 1998a,b;Lei et al, 2005] and cognitive process in humans [Cook et al, 2002;Crasson, 2003;Sienkiewicz et al, 2005]. In this article we report the results of the second part of our study [Del Seppia et al, 2006] on the effects of exposure to a magnetic field simulating the one encountered by the ISS on human attentional performance as evaluated by a series of standardized tests.…”