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Summary
Bats have been used as model animals to study their hearing,echolocation,ecological adaptation andevolution,and lots of remarkable results have been achieved.In order to adapt to echolocation,the structure andfunction of the auditory system in bats have developed distinct specializations.In the constant frequency-frequency modulation(CF-FM)bat cochlea,the so-called auditory fovea is formed,and the functionalorganization of auditory cortex is modular,which has become a representative specialized symbol.The latency ofneuronal response is not only a fundamental characteristic of bats,but also a part of the regulation of echolocationbehavior.It is found that neurons with longer latencies have sharper echo-delay tuning characteristics,whileneurons with shorter latencies have wider echo-delay tuning characteristics.Frequency tuning of bat auditoryneurons is far greater precision than humans and other non-echolocation animals.Moreover,the afferentsoriginating from the cochlear auditory fovea show overrepresentation of CF components of the second harmonicof echolocation signals at all levels of auditory centers,so as to meet the needs of target echo Doppler driftdetection.Duration is one of the actively changeable parameters of echolocating bat vocalization signals.Theduration-tuned neurons provide an important neural mechanism for encoding the temporal features of sound,matching the need for processing the temporal information of echolocation signals.Echo-delay tuned neuronshave been found in the auditory center of many echolocation bats,which not only can tune the target range,butalso the azimuth and elevation of the echo,thus playing an important role in the three-dimensional representationof the target location.In the inferior colliculus of CF-FM bats,neurons showed single-on and double-on responsepatterns to the CF-FM sound signal,which may be shaped by different local neural circuits.Based on the responseproperties of the auditory cortex neurons of mustached bats to echolocation signals,the auditory cortex neurons ofPteronotus parnellii can be divided into functional modules for processing different echo information.Forexample,neurons in CF/CF area are responsible for processing Doppler-shift magnitude,i.e.target velocity.Theneurons in FM/FM area are sensitive to echo delay or target distance.Studies on corticofugal control indicate thatthis control system provides a structural and functional guarantee for subcortical acoustic signal processing andplasticity changes in adaptation to the environment for adult bats.It has also been found that object-selectiveneurons exist in the auditory cortex of bats,which respond to auditory objects in a scale-invariant or size-constancy manner.This finding also provides evidence for the hypothesis that mammals follow a commonmechanism for scale invariance of hearing.The dynamic representation of3D space during flight not only existsin the cerebral cortex,but also in the auditory midbrain.It is now thought that different types of navigationneurons in the bats'brains perform their respective functions to guide them to their destinations in3D space and flight
