Dependence of the Startle Response on Temporal and Spectral Characteristics of Acoustic Modulatory Influences in Rats and Gerbils

Abstract

The acoustic startle response (ASR) and its modulation by non-startling prepulses, presented shortly before the startle-eliciting stimulus, is a broadly applied test paradigm to determine changes in neural processing related to auditory or psychiatric disorders. Modulation by a gap in background noise as a prepulse is especially used for tinnitus assessment. However, the timing and frequency-related aspects of prepulses are not fully understood. The present study aims to investigate temporal and spectral characteristics of acoustic stimuli that modulate the ASR in rats and gerbils. For noise-burst prepulses, inhibition was frequency-independent in gerbils in the test range between 4 and 18 kHz. Prepulse inhibition (PPI) by noise-bursts in rats was constant in a comparable range (8–22 kHz), but lower outside this range. Purely temporal aspects of prepulse–startle-interactions were investigated for gap-prepulses focusing mainly on gap duration. While very short gaps had no (rats) or slightly facilitatory (gerbils) influence on the ASR, longer gaps always had a strong inhibitory effect. Inhibition increased with durations up to 75 ms and remained at a high level of inhibition for durations up to 1000 ms for both, rats and gerbils. Determining spectral influences on gap-prepulse inhibition (gap-PPI) revealed that gerbils were unaffected in the limited frequency range tested (4–18 kHz). The more detailed analysis in rats revealed a variety of frequency-dependent effects. Gaps in pure-tone background elicited constant and high inhibition (around 75%) over a broad frequency range (4–32 kHz). For gaps in noise-bands, on the other hand, a clear frequency-dependency was found: inhibition was around 50% at lower frequencies (6–14 kHz) and around 70% at high frequencies (16–20 kHz). This pattern of frequency-dependency in rats was specifically resulting from the inhibitory effect by the gaps, as revealed by detailed analysis of the underlying startle amplitudes. An interaction of temporal and spectral influences, finally, resulted in higher inhibition for 500 ms gaps than for 75 ms gaps at all frequencies tested. Improved prepulse paradigms based on these results are well suited to quantify the consequences of central processing disorders.

Gap-induced reductions of evoked potentials in the auditory cortex: A possible objective marker for the presence of tinnitus in animals

“…This effect was not evident in gerbils ( Kiefer et al, 2015 , Steube et al, 2016 ) and another study failed to demonstrate frequency-dependency of GPIAS in rats ( Lobarinas et al, 2015 ). As Steube et al (2016) stated, it is possible that the frequency-dependency of GPIAS is different between species. Furthermore, as we used the same linear bandwidths for all background carrier frequencies, the higher frequency carriers would occupy narrower areas on the basilar membrane (due to its nonlinearity).…”

“…There are data in other rodents indicating that GPIAS is greater at higher frequencies compared to lower frequencies, although this was only evident in rats ( Steube et al, 2016 ) and mice ( Ison et al, 2005 ), wherein the most sensitive part of the audiogram is at higher frequencies than guinea pigs. This effect was not evident in gerbils ( Kiefer et al, 2015 , Steube et al, 2016 ) and another study failed to demonstrate frequency-dependency of GPIAS in rats ( Lobarinas et al, 2015 ). As Steube et al (2016) stated, it is possible that the frequency-dependency of GPIAS is different between species.…”

Effect of Long-Term Sodium Salicylate Administration on Learning, Memory, and Neurogenesis in the Rat Hippocampus

“…The control groups were treated with saline for 7 or 14 consecutive days. Behavior tests were performed 2 h after the last injection, as previously described [ 10 ].…”

GC-B Deficient Mice With Axon Bifurcation Loss Exhibit Compromised Auditory Processing

“…A cluster of afferent auditory neurons, the cochlear root neurons, gives rise to the ASR ( Lingenhohl and Friauf, 1994 ; Gomez-Nieto et al, 2014 ). The ASR is one of the fastest reflexes found in the mammalian central nervous system (CNS) ( Lauer et al, 2017 ) and a well-established behavioral test in awake animals to test for very fast auditory processing ( Steube et al, 2016 ). To study how impaired AN branching affects proper function of the ASR, acoustic startle behavior was measured in a subgroup of mice (GC-B WT: n = 5, GC-B KO: n = 7).…”