Study type: Technical/dosimetric study (experimental study)

Brain stem evoked responses associated with low-intensity pulsed UHF energy. med./bio.

Published in: J Appl Physiol 1967; 23 (6): 984-988

Aim of study (acc. to author)

The study was designed to be a parametric study of the effect of low-intensity pulse modulated ultra high frequency (UHF) energy on the functioning of the central nervous system. In this report, it is demonstrated that pulse modulated UHF energy at low power densities evokes potentials in the brain stem. The required experimental conditions are defined.



Exposure Parameters
Exposure 1: 1.2–1.525 GHz
Modulation type: pulsed
Exposure duration: more than 60000 pulses per session; exposures alternated with rest periods of 5 min

Exposure 1

Main characteristics
Frequency 1.2–1.525 GHz
Exposure duration more than 60000 pulses per session; exposures alternated with rest periods of 5 min
Additional info 1.2 GHz, 1.3 Ghz; 1.425 GHz, 1.525 GHz
Modulation type pulsed
Pulse width 10 µs
Packets per second 130
Additional info

12, 24, 36, 80, 130 pps

Exposure setup
Exposure source
Distance between exposed object and exposure source 0.5 m
Chamber non reflecting ecosorb test enclosure
Measurand Value Type Method Mass Remarks
power density 30 µW/cm² mean cf. remarks - -
power density 600 W/m² peak value cf. remarks - -

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • during exposure

Main outcome of study (acc. to author)

Evoked potentials in the brain stem were induced by illumination with pulse modulated UHF energy. The threshold power density necessary to evoke the responses was approximately 30 µW/cm² average and 60 mW/cm² peak. The results indicate that the potentials were neural rather than an artifact of the situation. Using an echosorb shield to cover the entire cat, or head, or body, it was found that the head must be exposed to the UHF energy in order to have an effect occur. Within the carrier-frequency range used (1.2-1.525 GHz), there seemed to be a reduction of effect at the highest frequency. Variation in power density has a distinct effect on the evoked potentials. Polarization of the energy, whether perpendicular or parallel to the spine, does not seem to have much effect though this is not unequivocal. As pulse-repetition frequency is changed, the evoked response does not change significantly until the pulse-repetition frequency is greater than approximately 50 pulses/sec. When greater than this, there is often an overlap of activity evoked by the series of stimuli.

Study character:

Study funded by