Radio waves mobile phones from appears to increase activity in parts of the brain that are closest to the devices, according to US Government antennas scientists.
Researchers found, 50 minute call led to a localized increase in brain activity of 7%, but they said there was no evidence to suggest the increase was harmful.
In order to exclude variation in brain activity, which would be expected when someone is listening to a call normally, changes in activity was monitored while the phone takes a call but was dampened.
Team, led by Nora volkow, Director of the National Institute on drug addiction in Maryland, found this brain activity increased in line with the strength of the electromagnetic field as the region specific brain was exposed.
Mobile phones use radio waves to send and receive calls and these produce small electromagnetic fields that can be absorbed by the head and brain.
"Even if we can't determine the clinical importance, our results provide evidence that the human brain is sensitive to the effects of radio frequency electromagnetic fields from acute cellphone exposures", said Dr. Volkow. the study appears in the Journal of the American Medical Association.
The dramatic increase in mobile phone use in the world has prompted concern about the possible adverse effects, including brain tumours. Last year, it was very late Interphone report no hard evidence that mobile phones increase the risk of cancer, but the question remains unresolved.
In the new survey had 47 voluntary two brain scans, each on different days. Scans, which used a technique known as positron emission tomography (PET), was designed to monitor changes in the way, the brain becomes glucose, fuel it requires to work.
Before being scanned, volunteers had a mobile phone located at each ear. In one scan, were both phones switched off. But in others the scan, the phone on the right ear was turned on, muted and set to receive a lengthy recorded message. Volunteers were given not to know what scanning was like.
When they compared scans taken in these two different scenarios, Volkow's team discovered a pattern of increased brain activity in the right orbitofrontal cortex and the right superior temporal gyrus lower parts. In these areas of the brain increased glucose metabolism from 33.3 to 35.7 micromoles of glucose per 100 g every minute.
Brain activity may increase much more than this, when a person just look at the images on a screen. In 2006, Andrei Vlassenko at Washington University School of Medicine reported to show images could increase brain activity by between six and 51%. Vokow said these increases were caused by way of thinking about images, while mobile phones appeared to increase activity "artificially".
She said it was unclear how mobile phone radiation can affect the brain metabolism and added that more research was needed to examine whether the effects could be harmful. Since completing the investigation, she is started by using a set with his mobile phone, a Move she described as "conservative, not paranoid".
If increases in brain activity caused by mobile phone use is, however, to be harmless, Volkow said, this phenomenon could be used to stimulate patients have underactive brain regions.
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