Effects of Electromagnetic Radiation from Smartphones on Learning Ability and Hippocampal Progenitor Cell Proliferation in Mice

Effects of Electromagnetic Radiation from Smartphones on Learning Ability and Hippocampal Progenitor Cell Proliferation in Mice

Yu-Jin Choi, Yun-Sik Choi. Effects of Electromagnetic Radiation from Smartphones on Learning Ability and Hippocampal Progenitor Cell Proliferation in Mice. Osong Public Health and Research Perspectives. Available online 23 December 2015. 

Abstract

Objectives

Nonionizing radiation is emitted from electronic devices, such as smartphones. In this study, we intended to elucidate the effect of electromagnetic radiation from smartphones on spatial working memory and progenitor cell proliferation in the hippocampus.

Methods

Both male and female mice were randomly separated into two groups (radiated and control) and the radiated group was exposed to electromagnetic radiation for 9 weeks and 11 weeks for male and female mice, respectively. Spatial working memory was examined with a Y maze, and proliferation of hippocampal progenitor cells were examined by 5-bromo-2′-deoxyuridine administration and immunohistochemical detection.

Results

When spatial working memory on a Y maze was examined in the 9^th week, there was no significant difference in the spontaneous alternation score on the Y maze between the two groups. In addition, there was no significant difference in hippocampal progenitor cell proliferation. However, immunoreactivity to glial fibrillary acidic protein was increased in exposed animals. Next, to test the effect of recovery following chronic radiation exposure, the remaining female mice were further exposed to electromagnetic radiation for 2 more weeks (total 11 wk), and spontaneous alternation was tested 4 weeks later. In this experiment, although there was no significant difference in the spontaneous alternation scores, the number of arm entry was significantly increased.

Conclusion

These data indicate that although chronic electromagnetic radiation does not affect spatial working memory and hippocampal progenitor cell proliferation it can mediate astrocyte activation in the hippocampus and delayed hyperactivity-like behavior.
The abstract does not appear in PubMed.
Excerpts

Mice were divided into two groups: animals from the exposed group were housed in a cage that was placed on the smartphone (Galaxy K, Samsung Electronics, South Korea) and it was maintained on operating mode throughout the study. To imitate the condition of daily smartphone use in life, we called and let mice hear the sound from the smartphone for 10 minutes a day. In the control group, animals were housed under normal conditions without electromagnetic radiation exposure. Mice were exposed to electromagnetic radiation for 9 weeks, and spontaneous alternation was tested. To verify the effect of recovery following electromagnetic radiation exposure, female mice were further exposed to electromagnetic radiation for 2 more weeks. After the smartphone was removed, female mice were housed under normal conditions for 4 weeks to provide a recovery period, and spontaneous alternation was tested (Figure 1).
In our study, there was no significant difference in progenitor cell proliferation in the hippocampus and in spatial working memory. However, some reports indicate that electromagnetic radiation influences progenitor cell proliferation and/or spatial working memory [14,15]. The reason for the discord is unknown, although it is worth noting that we provided exposure to electromagnetic radiation for a relatively long term.
... we exposed electromagnetic radiation to female mice for 11 weeks and provided a recovery period under normal housing condition for
4 weeks. To our surprise, although the percentage of spontaneous alternation was not affected, the number of arm entries was significantly increased by providing a recovery for 4 weeks following an 11-week-long period of exposure to a radiation field. These data further support the previous evidence showing that exposure to electromagnetic radiation may be able to induce delayed hyperactivity-like behavior.
Interestingly, recent data indicate that although electromagnetic fields influence learning and memory in rodents, the animals can adapt to long-term exposure [16]. In addition, long-term whole-body exposure to an electromagnetic field from a mobile phone does not cause any adverse effects on memory function and development [17]. Therefore, it is tempting to hypothesize that our nervous system can adapt to long-term exposure to electromagnetic radiation from smartphones. However, we cannot exclude the possibility that acute whole-body exposure to electromagnetic radiation changes working memory and/or hippocampal progenitor cell proliferation. Further study will be needed to elucidate this hypothesis.
In summary, we provided herein further solid evidence supporting the hypothesis that chronic exposure to electromagnetic radiation may induce delayed hyperactivity-like behavior without affecting spatial working memory and hippocampal progenitor cell proliferation.

-- 
Joel M. Moskowitz, Ph.D., Director
Center for Family and Community Health
School of Public Health
University of California, Berkeley

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