Prepulse Inhibition of Acoustic Startle Reflex as a Function of the Frequency Difference between Prepulse and Background Sounds in Mice

Sidhesh Basavaraj,Jun Yan,Manuel S Malmierca

doi:10.1371/journal.pone.0045123

Abstract

BackgroundPrepulse inhibition (PPI) depicts the effects of a weak sound preceding strong acoustic stimulus on acoustic startle response (ASR). Previous studies suggest that PPI is influenced by physical parameters of prepulse sound such as intensity and preceding time. The present study characterizes the impact of prepulse tone frequency on PPI.MethodsSeven female C57BL mice were used in the present study. ASR was induced by a 100 dB SPL white noise burst. After assessing the effect of background sounds (white noise and pure tones) on ASR, PPI was tested by using prepulse pure tones with the background tone of either 10 or 18 kHz. The inhibitory effect was assessed by measuring and analyzing the changes in the first peak-to-peak magnitude, root mean square value, duration and latency of the ASR as the function of frequency difference between prepulse and background tones.ResultsOur data showed that ASR magnitude with pure tone background varied with tone frequency and was smaller than that with white noise background. Prepulse tone systematically reduced ASR as the function of the difference in frequency between prepulse and background tone. The 0.5 kHz difference appeared to be a prerequisite for inducing substantial ASR inhibition. The frequency dependence of PPI was similar under either a 10 or 18 kHz background tone.ConclusionPPI is sensitive to frequency information of the prepulse sound. However, the critical factor is not tone frequency itself, but the frequency difference between the prepulse and background tones.

Highlights

Swift reaction to an unexpected sensory stimulus is exhibited in various species of animals including humans [1,2,3]
prepulse inhibition (PPI) is positively correlated with the difference in intensity between prepulse and background sounds [25]. These results suggest that the acoustic startle response (ASR) magnitude varies depending on acoustic environment, whereas PPI is tightly correlated to the intensity, duration and preceding time of prepulse sound
The present study addresses the impact of frequency differences between prepulse and background tones on PPI

Summary

Introduction

Swift reaction to an unexpected sensory stimulus is exhibited in various species of animals including humans [1,2,3]. Apart from the influence of sensory signals in the environment on ASR, a weak auditory, visual or somatosensory signal shortly preceding the startle sound can remarkably attenuate the startle response [7,8,9,10,11,12]. This so-called prepulse inhibition (PPI) functions as a sensorimotor gating mechanism that allows the brain to exclude or suppress unnecessary or unrelated sensory inputs [13,15]. The present study characterizes the impact of prepulse tone frequency on PPI

Methods

Results

Conclusion