Beasond R C, Semm P (2002):
Thirty four adult zebra finches were used in this study. They were anaesthetized and placed in a chamber in such a way that their head was at the centre, and exposed to RF radiation of 900 MHz, pulse-modulated at 217 Hz. The average SAR was 0.05 W/kg. A small hole was made in the skull and electrodes inserted to enable electrical activity from neurons (brain nerve cells) to be recorded. Recordings were made from 134 neurons. A 10-minute pre-stimulus period was used for baseline measures, and this was followed by a 10-minute stimulus period and then by a 10-minute post-stimulus period. The recording sites were in the cerebrum and the anterior cerebellum.
Ninety one units showed some response to the stimulation. Sixty nine (52%) responded with excitation, with increases in their rate of firing of about 3.5-fold on average. Another 22 (17%) had decreased rates of firing. The remaining 42 showed no response. In half of the responding cells the response lasted beyond the end of the stimulus period. The mean persistence beyond the end of the stimulus period was 308 ± 68 seconds.
Three cells that responded to the stimulus were also tested with an unmodulated signal of the same carrier frequency. None of these cells showed a response.
Further investigation is warranted. Sham exposures, and extension of the experiments with an unmodulated signal, should be included in future studies.