Behaviorally relevant frequency selectivity in single- and double-on neurons in the inferior colliculus of the Pratt's roundleaf bat, Hipposideros pratti.

Ziying Fu,Qing Shi,Dandan Zhou,Guimin Zhang,Jia Tang,Qicai Chen,Long Liu,Manuel S. Malmierca

doi:10.1371/journal.pone.0209446

Ziying Fu, Qing Shi + Show 6 more

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https://doi.org/10.1371/journal.pone.0209446

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Abstract

Frequency analysis is a fundamental function of the auditory system, and it is essential to study the auditory response properties using behavior-related sounds. Our previous study has shown that the inferior collicular (IC) neurons of CF-FM (constant frequency-frequency modulation) bats could be classified into single-on (SO) and double-on (DO) neurons under CF-FM stimulation. Here, we employed Pratt's roundleaf bats, Hipposideros pratti, to investigate the frequency selectivity of SO and DO neurons in response to CF and behavior-related CF-FM sounds using in vivo extracellular recordings. The results demonstrated that the bandwidths (BWs) of iso-frequency tuning curves had no significant differences between the SO and the DO neurons when stimulated by CF sounds. However, the SO neurons had significant narrower BWs than DO neurons when stimulated with CF-FM sounds. In vivo intracellular recordings showed that both SO and DO neurons had significantly shorter post-spike hyperpolarization latency and excitatory duration in response to CF-FM in comparison to CF stimuli, suggesting that the FM component had an inhibitory effect on the responses to the CF component. These results suggested that SO neurons had higher frequency selectivity than DO neurons under behavior-related CF-FM stimulation, making them suitable for detecting frequency changes during echolocation.

Highlights

IntroductionFM (frequency modulation) sounds are mainly used by bats preying in open space environments, while CF-FM (constant frequency-FM) sounds are employed by bats (called CF-FM bats) as echolocation signals for hunting in relatively complex environments, such as forests and brushwoods [1]
frequency modulation (FM) sounds are mainly used by bats preying in open space environments, while constant frequency (CF)-FM sounds are employed by bats as echolocation signals for hunting in relatively complex environments, such as forests and brushwoods [1]
An earlier study on collicular evoked responses showed typical response to both the CF and the FM components of simulated behavior-related sounds [33], but the authors did not assess the changes in the duration of the CF or FM components to verify whether the response to FM component was an on- or off-response

Summary

Introduction

FM (frequency modulation) sounds are mainly used by bats preying in open space environments, while CF-FM (constant frequency-FM) sounds are employed by bats (called CF-FM bats) as echolocation signals for hunting in relatively complex environments, such as forests and brushwoods [1]. Which is known as Doppler shift [3, 4]. These bats have to deal with complex sound signals in heavy background noise conditions. In order to adapt to these complicated conditions, CF-FM bats have evolved some auditory system mechanisms, including an auditory fovea in the cochlea and Doppler shift compensation area in the auditory cortex, which are responsible for fine frequency analysis [5,6,7]

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