Ntzouni MP, Stamatakis A, Stylianopoulou F, Margaritis LH. Short-term memory in mice is affected by mobile phone radiation. Pathophysiology. Nov 25, 2010. Ahead of print.
Mobile phone use has increased exponentially over the last decade and there is a deep public concern that frequent use and hence, frequent exposure to electromagnetic fields (EMF) effects brain development, function, and memory. Although a considerable amount of research has focused on memory and learning deficits, the published data is controversial and has a range of outcomes from no effects to worrisome effects that require further investigations. This group attempts to tackle many unknown questions including both acute and chronic exposure to EMF and the effect that is has on short-term memory.
The objective of this study was to determine the effects of acute and chronic mobile phone exposure on mouse short-term memory function.
Three separate groups of 8 young male mice were used in each memory study: the first group was exposed to the EMF through three different phases of exposure, the second group was sham-exposed and the third group were left in their cages. The memory test involved three days of activity. Day1 (habituation session), the mice were allowed to explore the apparatus for 5 minutes. Day 2 (acquisition phase), the mice were allow to explore two identical objects placed at opposite ends of the apparatus for 10 minutes. Day 3 (test session), the mice were exposed to two trials in the apparatus. The first trial the objects placed in the apparatus were the same as Day 2 objects and the mice were allowed to explore these for 10 minutes (Test 1). The mice were then removed and after a 10 minute interval (known as inter-trial interval), the mice were placed in the apparatus again with one object the same as in Test 1 and one new object (Test 2). The memory test is based on the time the mouse spent exploring the new versus the familiar object. The inter-trial interval between the two tests is considered to be a memory consolidation phase where a memory is stabilized after initial acquisition. Three different combinations of exposure to EMF before and three separate memory tests were used in this experiment: 1) acute exposure: mice were exposed to EMF during day 1, 2 and 3 of the memory test. They were not exposed during the inter-trial period. 2) Chronic exposure-I: the same mice were then exposed to EMF for 17 days at 90 min/day. The mice were exposed to their daily 60 minutes before the memory test began but not exposed during the actual test itself. On day 3 the mice were exposed an additional 10 during the inter-trial interval but not during the tests themselves. 3) Chronic exposure II: the same mice continued daily exposure for 31 days. The memory test was then performed one day after the last EMF exposure and mice were not exposed during any part of the three day memory test.
The researchers found that mice exposed to long term EMF radiation in the second phase of the experiment, chronic exposure I, had a significantly reduced short-term memory function compared to the sham-exposed mice. In this phase, the mice were exposed to EMF during the inter-trial interval, and the investigators surmised that the poor memory performance was due to EMF exposure during this phase.
Interpretation and Limitations
The researchers concluded that exposure to EMF during the inter-trial interval phase interfered with the establishment of memory in the brain. However the acute phase and the chronic 31 day exposure (without the inter-trial interval phase exposure) did not show any significant decrease in short-term memory. It should also be noted that the same mice were used for all three phases of the experiment. Therefore although the mice were compromised during the second phase of the experiment, during the third phase they seemed to have regained their short-term memory function even though the mice had been exposed to an additional 14 days of radiation.
This study suggests that exposure to EMF interferes or slows the stabilization process of memory in the brain.