These authors previously reported that exposure to radiofrequency electromagnetic fields (RF EMF) was associated with an increase in regional cerebral blood flow. In the present study they compared the effects of a "base-station-like" (bstat) signal with a "handset-like" (handset) signal.

Sixteen healthy, right-handed men (mean age 22.5 years) participated, but because of "technical problems and logistical reasons" only 12 subjects completed the entire study. After a normal sleep, the subjects' left hemispheres were exposed for 30 minutes to the RF EMF at a frequency of 900 MHz. The spatial peak average SAR over 10g was 1.0 W/kg. The experiment consisted of a double-blind, sham-controlled, crossover design with two active conditions (bstat and handset). The handset signal consisted of a generic signal with a similar spectral content as the one emitted by a GSM mobile phone. The bstat signal mimicked the signal modulation emitted by a GSM base station. The interval between the exposure conditions was at least one week.

Cerebral blood flow was measured by PET scan. The interval between the end of the exposure and the first PET scan was 10 minutes.

The authors observed an increase in relative regional blood flow in the dorsolateral prefrontal cortex on the side of the exposure. This was seen only with the handset exposure. The authors state:

"This finding supports our previous observation that pulse modulation of RF EMF is necessary to induce changes in the waking and sleeping EEG, and substantiates the notion that pulse modulation is crucial for RF EMF-induced alterations in brain physiology".