Single microwave pulses can suppress startle reflexes in mice

Modification of the acoustic startle reflex (ASR) exhibited by mice was used as a basis for determining the neural effectiveness of single microwave pulses (1 to 10 mu s, 1250 MHz). The authors utilized a tail clamp body motion detector to monitor the ASR while the mice were constrained within an exposure chamber which focused microwave energy selectively in the head and neck region. Complete suppression of the ASR was seen when single microwave pulses yielding absorbed energies of 0.2 J/kg or more were applied anywhere from 500 to 5 ms before the sound burst. Partial suppression of the ASR could be seen with even lower energy pulses or with pulses delivered over a wider range of prestimulus delays. These results cannot be attributed to bulk thermal effects, but may be due to thermoelastic or microthermal phenomena leading to neural intervention acting at the cochlea or within the CNS.<>