Fourteen healthy, right-handed male volunteers took part in this study. They performed a memory task twice - once during exposure to a RF field, and once during sham exposure. The sequence of exposure order was counterbalanced. A GSM phone was used as the exposure source. The loudspeaker was removed so that the subject was not aware of the exposure condition. The experimenters were also unaware of the exposure status.
The phone was mounted on the left side of the subject's head with the site of the removed loudspeaker over the ear canal and the microphone towards the corner of the mouth. The phone emitted a 902 MHz frequency EMF, with a mean power of 0.25 W, pulsed at a frequency of 217 Hz, and a pulse width of 0.577 ms. The SAR was 0.993 W/kg with an extrapolated peak value of 2 W/kg. The whole session took 90 minutes, with the EMF active for half the time. Cerebral blood flow was measured using PET scans.
The EMF exposure had no effect on reaction times or accuracy of the responses in the memory task.
During exposure there was reduced blood flow in an area of the left temporal lobe, compared to sham exposure. There was also reduced blood flow in the same area of the right temporal lobe, but it was considerably less pronounced. There was no significant change in cerebral blood flow elsewhere in the brain.
These results are different from those of Huber et al. (2002), who found increased blood flow in the prefrontal cortex of the same side of the brain as the exposure. However, Huber and colleagues performed the PET scan 10 minutes after exposure, and their subjects did not perform any tests of cognitive function.
The authors offer two possible explanations for the decrease in blood flow in the temporal lobe. The first is that, since other studies have shown effects remote from the area of maximum EMF exposure, the observed effect may be due to the EMF field. The other possibility, and one that the authors think more likely, is that the observed effect was due to a high frequency signal that was emitted from the phone's battery. While this "was too weak to be consciously perceived, it might lead to deactivation in the auditory cortices while the subjects are attending to the visual task at hand."