Impact of stimulus signal-to-noise ratio on prepulse inhibition of acoustic startle


  • Portions of this research were supported by a grant from the Wake Forest University Social Science Research Fund.

Address reprint requests to: Terry D. Blumenthal, Department of Psychology, Wake Forest University, Winston-Salem, NC 27109, USA. E-mail:


Prepulse inhibition (PPI) of the human acoustic startle response is reduced in the presence of background noise of a sufficient intensity, possibly due to a reduction in signal-to-noise ratio (prepulse intensity relative to background noise). We examined this hypothesis by varying prepulse intensity and background noise intensity in order to hold three different signal-to-noise ratios constant (5, 15, and 25 dB(A) above background noise intensity). The results showed that signal-to-noise ratio proved to be a more important factor than absolute stimulus intensity in determining the degree of PPI of startle eyeblink response magnitude. Therefore, the effectiveness of a prepulse is determined by prepulse salience, not intensity, and this effectiveness is equivalent across a range of physical intensities.