Cell phone emissions excite the part of the brain cortex nearest to the phone, but it is not clear if these effects are harmful, Italian researchers reported on June 26.
Their study, published in the Annals of Neurology, adds to a growing body of research about mobile phones, their possible effects on the brain, and whether there is any link to cancer.
Dr Paolo Rossini of Fatebenefratelli hospital in Milan and colleagues used Transcranial Magnetic Stimulation or TMS to check brain function while people used these phones.
The cortex is the outside layer of the brain and the motor cortex is known as the "excitable area" because magnetic stimulation has been shown to cause a muscle twitch.
The researchers stressed that they had not shown that using a cell phone is bad for the brain in any way, but people with conditions such as epilepsy, linked with brain cell excitability, could potentially be affected.