ROME - Cell phone signals alter the excitability of the nearby motor cortex, according to researchers here, who don't know what the finding means, if anything.
ROME, June 26 - Cell phone signals alter the excitability of the nearby motor cortex, according to researchers here, who don't know what the finding means, if anything.
In 12 of 15 volunteers, 45 minutes of exposure to the electromagnetic field emitted by a standard cell phone resulted in noticeable changes in motor cortex excitability, said the researchers, led by Paolo Maria Rossini, M.D., Ph.D., of the Hospital Fatebenefratelli here.
"Intracortical excitability was significantly modified," they reported in the July issue of Annals of Neurology. "Short intracortical inhibition was reduced and facilitation enhanced." The effects were transient and the subjects' brains tended to return to baseline within an hour of exposure.
"This study has shown definitively an effect of cellular phone emissions on the excitability of the motor cortex adjacent to the electromagnetic field source," Dr. Rossini and colleagues said.
But, they added, "we still do not know whether this effect is neutral or potentially dangerous or beneficial to cortical and brain functioning." They suggested further study, both in healthy participants and in those suffering from neurological diseases characterized by altered cortical excitability, such as epilepsy.
Cell phone signals have been studied for several years, mainly because of fears they could somehow cause cancer. But a major study published in January by British researchers - the largest analysis of the issue - found no link between cell phone use and brain cancer.
Dr. Rossini and colleagues used transcranial magnetic stimulation - a non-invasive method of brain imaging - to carry out their study, which they said is the first to report the effect of electromagnetic field exposure on the physiology of the brain.
They recruited 15 male volunteers, ranging in age from 15 to 36, for a crossover, double-blind study, in which the participants were exposed either to 45 minutes of signals from a commercially available cell phone or to a sham exposure of the same length.
The phone was mounted in a helmet that kept it a constant 15 millimeters from the participant's left ear; an identical phone, but without a battery, was mounted on the other side of the helmet. On both sides, the aerial was about 40 mm from the scalp, and positioned over the parietal-temporal area.
The volunteers had two sessions, one in which the power to the phone was on and one with the power off; changes in motor cortex excitability were measured by transcranial magnetic stimulation.
Averaged over all the participants, the right hemispheres of the brains showed no changes between the real and sham condition, Dr. Rossini and colleagues found, because the dummy phone was positioned on that side.
However, on the left, the researchers noted a significant alteration (at P<0.001) in excitability at the end of the real exposure, compared to the sham exposure.
When they looked at the data for each participant, Dr. Rossini and colleagues said, they saw the same pattern in 12 of the 15.