The use of wireless communication devices in both the private and the public sector continues to grow. Even though more and more studies on the impact of microwave radiation on human health are being published, there is no unanimous consensus on the negative effects. Data from several studies indicate that 2.45 GHz microwave radiation (emitted by e.g. Wi-Fi routers) leads to cognitive impairment. Exposure to both continuous and pulsed microwaves leads to increased neuronal cell death in the hippocampus. The hippocampus is a distinct structure of the brain and represents a central node of the limbic system. The neuronal damage in the brain due to microwaves is caused by the excessive production of free radicals and reactive oxygen species (ROS). Negative effects of microwave radiation have been challenged by several studies, which showed that whole-body exposure to 2.45 GHz microwave radiation has no effect on learning and memory formation. The authors of the present study examined the effect of microwave radiation on the hippocampal region, memory performance and parameters of synaptic plasticity. Synaptic plasticity is closely related to memory formation by changing the strength of a synaptic transmission. Therefore, the frequent use of certain synapses allows easier excitement of postsynaptic neurons.
This study was conducted with adult male Sprague Dawley rats. Twenty-one rats took part in the experiments: 11 animals were exposed, 10 animals were sham-exposed and served as the controls. The sham group underwent the same exposure procedure as the exposure group, but the radiation source was switched off. A 2.45 GHz Wi-Fi device was used to expose the rats for two hours a day for a total of 40 days. This resulted in a whole-body SAR value of 0.017 W/kg. After the exposure period, behavioral tests were conducted to address memory performance. First, a radial arm mace test was performed. Depending on how fast and reliably the rats pass through the mace, conclusions can be drawn about their memory performance. In addition, the animals were subjected to a passive avoidance test. During the learning phase, the animals were placed in the white chamber of an apparatus consisting of two chambers. When entering the dark chamber, the passage between both chambers was closed and the animals suffered
an electric shock through the floor grid. In the actual experiment, the time when the animals entered the dark chamber was recorded. After completion of the passive avoidance test, an electrophysiological study was carried out. The neuronal stimulus transmission in the hippocampus was investigated by use of field electrodes. Afterwards, the cell physiology of the rat brain was evaluated by histochemical methods.
The microwave radiation led to deficits in learning behavior and spatial memory performance of the experimental animals. During the learning phase of the radial arm mace test, the exposed animals were significantly slower in meeting the experimental criteria. In addition, significantly more mistakes were made during the experiment and the exposed animals required more time to pass through the mace. During the avoidance test, the animals of the exposed group went statistically significantly faster into the dark chamber. The electrophysiological study showed a reduced excitability of CA1 pyramidal neurons of the hippocampus after exposure. The difference was statistically significant between a stimulation strength of 450 and 1200 μA (minimum stimulation 50 μA, maximum stimulation 1200 μA). Furthermore, the scientists were able to show that microwave radiation has a negative effect on long-term, but not short-term synaptic plasticity. The histochemical approach discovered a statistically significant reduction in the number of CA1 pyramidal neurons in the brain of exposed rats.
The researchers were able to show that 2.45 GHz microwave radiation from a Wi-Fi device impairs the spatial memory formation and learning behavior in rats. To understand the cause of this deterioration, the scientists performed an electrophysiological study that suggests a reduced excitability of hippocampal pyramidal neurons. In addition, the synaptic plasticity of the neurons seems to be adversely affected in the long term.