P50 suppression and prepulse inhibition of the startle reflex in humans: Acorrelational study

Background: Sensory gating is an important feature of the normally function ing brain. When not operating correctly, it can contribute to different kin ds of psychiatric illnesses by flooding the higher brain functions with use less information. Over the years, two paradigms have evolved to quantify th e amount of sensory gating: the prepulse inhibition (PPI) of the startle re flex and the suppression of the P50 evoked potential. To enable comparison across studies it is important to find out to what extent these paradigms r eflect the same processes. In the present study, this relationship was expl ored. Methods Thirty-one healthy male volunteers with no personal or family histo ry of mental illness were tested on their ability to suppress the P50 wave and to inhibit the startle reflex. Results: A significant positive correlation was found between PPI and P50 s uppression mainly early in testing, when habituation of the startle reflex is taking place. Furthermore, a significant negative correlation was found between P50 suppression in the second half of testing and the habituation o f the startle reflex. Conclusions: PPI and P50 suppression are correlated at an early stage of te sting, when the process of habituation of the startle reflex is active. The role of the habituation in the correlation between these two measures need s to be further explored. (C) 1999 Society of Biological Psychiatry.