Sensory gating of the P13 midlatency auditory evoked potential and the startle response in the rat

The human P1/P50 midlatency auditory evoked potential and the startle response (SR) have been used as measures of sensory and sensorimotor gating, respectively. In the present study, both prepulse and paired stimulus paradigms were used in order to investigate the relationship between sensory gating mechanisms of the P13 potential, the putative rodent equivalent of the P1 potential, and those of the SR. In addition, these were compared to the properties of the N40 potential, another measure of sensory gating. Simultaneous recordings from the vertex (P13 potential and N40 potential) and neck musculature (SR) showed that (1) in a prepulse paradigm, increasing the intensity of the prepulse or decreasing the interstimulus interval resulted in increased inhibition of the P13 potential, N40 potential (to a lesser degree) and the SR (to a greater degree), (2) when using a low signal-to-noise ratio between the prepulse intensity and the background level, prepulse inhibition of the SR was reduced or absent while that of the P13 potential was present, (3) the amplitude of the 'prepulse evoked' P13 potential was significantly correlated with prepulse inhibition of the P13 potential, the N40 potential and the SR, (4) in a paired identical stimulus paradigm, decreasing the interstimulus interval resulted in increased habituation of the P13 potential, N40 potential (to a lesser degree) and the SR, and (5) increasing the intensity of the paired stimulation resulted in increased habituation of the P13 potential and the N40 potential (to a lesser degree), but not of the SR. These results demonstrate the presence of prepulse inhibition of the P13 potential, the N40 potential and the SR in a parallel manner, but show certain specific differences in their responses to parametric changes.