The design and calibration of a startle measurement system

The present study sought to determine appropriate instrumentation for amplification and calibration of cages used to measure the acoustic startle response in rats. Fourier analysis indicated that the characteristic frequency of the rat startle response is about 5-15 Hz. This value was consistent in cages differing widely in resonant frequency, among several different transducers and across a range of large and small startle responses. Given this characteristic frequency range of startle, it is suggested that amplifiers fitted with band pass filters centered at about 10 Hz should be ideal for measuring startle while simultaneously excluding non-startle activity. A device is described which vibrates startle cages at 10 Hz, since this seems most appropriate for calibrating the sensitivity of a startle system. Data are presented showing that this type of calibrator is more valid than an impact-type calibrator.