Operant behavior and colonic temperature of Macaca mulatta exposed to radio frequency fields at and above resonant frequencies med./bio.

To study operant behavior and colonic temperature of rhesus monkeys exposed to radiofrequency fields and to determine the minimal power densities affecting performance.

The animals were trained to press a lever (observing-response) thereby producing signals that indicated availability of food. In the presence of the aperiodically appearing food signals, a detection response on a different lever was reinforced by food.

• animal
• rhesus monkey (Macaca mulatta)
• whole body

Observing-response performance was impaired at increasingly higher power densities as frequency increased from the near-resonance 225 MHz to the above-resonance 5.8 GHz.
The threshold power density of disrupted response rate at 225 MHz was 8.1 mW/cm²; at 1.3 GHz it was 57 mW/cm², and at 5.8 GHz it was 140 mW/cm². These power densities were associated with reliable increases in colonic temperatures above sham-irradiated levels. The mean increase was in the range of 1°C, and response-rate changes were not found in the absence of concomitant temperature increases.
In these experiments elevation of colonic temperature was a much better predictor of behavioral disruption than was either the power density of the incident field or estimates of whole-body-averaged rates of energy absorption.