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

Background: Sensory gating is an important feature of the normally functioning brain. When not operating correctly, it can contribute to different kinds of psychiatric illnesses by flooding the higher brain functions with useless information. Over the years, two paradigms have evolved to quantify the amount of sensory gating: the prepulse inhibition (PPI) of the startle reflex and the suppression of the P50 evoked potential. To enable comparison across studies it is important to find out to what extent these paradigms reflect the same processes. In the present study, this relationship was explored. Methods: Thirty-one healthy male volunteers with no personal or family history 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 suppression 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 of the startle reflex. Conclusions: PPI and P50 suppression are correlated at an early stage of testing, when the process of habituation of the startle reflex is active. The role of the habituation in the correlation between these two measures needs to be further explored.