Prepulse inhibition predicts subjective hearing in rats

Naoki Wake,Taiki Abe,Kotaro Ishizu,Hirokazu Takahashi

doi:10.1038/s41598-021-98167-6

Abstract

Auditory studies in animals benefit from quick and accurate audiometry. The auditory brainstem response (ABR) and prepulse inhibition (PPI) have been widely used for hearing assessment in animals, but how well these assessments predict subjective audiometry still remains unclear. Human studies suggest that subjective audiometry is consistent with the ABR-based audiogram, not with the PPI-based audiogram, likely due to top-down processing in the cortex that inhibits PPI. Here, we challenged this view in Wistar rats, as rodents exhibit less complexity of cortical activities and thereby less influence of the cerebral cortex on PPI compared to humans. To test our hypothesis, we investigated whether subjective audiometry correlates with ABR- or PPI-based audiograms across the range of audible frequencies in Wistar rats. The subjective audiogram was obtained through pure-tone audiometry based on operant conditioning. Our results demonstrated that both the ABR-based and PPI-based audiograms significantly correlated to the subjective audiogram. We also found that ASR strength was information-rich, and adequate interpolation of this data offered accurate audiometry. Thus, unlike in humans, PPI could be used to predict subjective audibility in rats.

Highlights

Auditory studies in animals benefit from quick and accurate audiometry
As prepulse inhibition (PPI) is derived from the acoustic startle reflex (ASR)—which is influenced by indirect projections from many brain regions (e.g., from the auditory cortex to the caudal pontine reticular nucleus (PnC)26–29)—inter-species differences in neural activities that inhibit ASR may cause a discrepancy between subjective audibility and the PPI-based audiogram
Assuming that the top-down control of the ASR may be qualitatively different in rodents than in humans, the present study challenged the conventional view of discrepancies between subjective audibility and PPI-based audiograms in Wistar rats

Summary

Introduction

Auditory studies in animals benefit from quick and accurate audiometry. The auditory brainstem response (ABR) and prepulse inhibition (PPI) have been widely used for hearing assessment in animals, but how well these assessments predict subjective audiometry still remains unclear. Human studies suggest that subjective audiometry is consistent with the ABR-based audiogram, not with the PPI-based audiogram, likely due to top-down processing in the cortex that inhibits PPI. We challenged this view in Wistar rats, as rodents exhibit less complexity of cortical activities and thereby less influence of the cerebral cortex on PPI compared to humans. PPI-based audiograms are in close agreement with ABR-based audiograms in mice[12], suggesting that unlike in humans, PPI-based audiograms in Wistar rats predict subjective audibility. We demonstrated that the PPI-based audiograms of rats were closely correlated with subjective audibility as well as ABR-based audiograms, supporting the hypothesis that PPI-based hearing tests are reliable in Wistar rats

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