Editing Animal echolocation (section)

===== Inner ear and primary sensory neurons =====

Both CF and FM bats have specialized inner ears which allow them to hear sounds in the ultrasonic range, far outside the range of human hearing. Although in most other aspects, the bat's auditory organs are similar to those of most other mammals, certain bats ([[horseshoe bats]], ''Rhinolophus spp.'' and the [[moustached bat]], ''Pteronotus parnelii'') with a constant frequency (CF) component to their call (known as high duty cycle bats) do have a few additional adaptations for detecting the predominant frequency (and harmonics) of the CF vocalization. These include a narrow frequency "tuning" of the inner ear organs, with an especially large area responding to the frequency of the bat's returning echoes.<ref name="Neuweiler_2003"/>

The [[basilar membrane]] within the [[cochlea]] contains the first of these specializations for echo information processing. In bats that use CF signals, the section of the membrane that responds to the frequency of returning echoes is much larger than the region of response for any other frequency. For example, in the greater horseshoe bat, ''[[Rhinolophus ferrumequinum]]'', there is a disproportionately lengthened and thickened section of the membrane that responds to sounds around 83&nbsp;kHz, the constant frequency of the echo produced by the bat's call. This area of high sensitivity to a specific, narrow range of frequency is known as an "[[acoustic fovea]]".<ref>{{cite journal |last1=Schuller |first1=G. |last2=Pollack |first2=G. |year=1979 |title=Disproportionate frequency representation in the inferior colliculus of Doppler-compensating greater horseshoe bats: Evidence of an acoustic fovea | journal=Journal of Comparative Physiology A |volume=132 |issue=1 | pages=47–54 |doi=10.1007/bf00617731 | s2cid=7176515 |url=https://epub.ub.uni-muenchen.de/3159/ |url-access=subscription }}
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Echolocating bats have cochlear hairs that are especially resistant to intense noise. Cochlear hair cells are essential for hearing sensitivity, and can be damaged by intense noise. As bats are regularly exposed to intense noise through echolocation, resistance to degradation by intense noise is necessary.<ref>{{Cite journal |last1=Liu |first1=Zhen |last2=Chen |first2=Peng |last3=Li |first3=Yuan-Yuan |last4=Li |first4=Meng-Wen |last5=Liu |first5=Qi |last6=Pan |first6=Wen-Lu |last7=Xu |first7=Dong-Ming |last8=Bai |first8=Jing |last9=Zhang |first9=Li-Biao |last10=Tang |first10=Jie |last11=Shi |first11=Peng |display-authors=3 |date=November 2021 |title=Cochlear hair cells of echolocating bats are immune to intense noise |url=https://linkinghub.elsevier.com/retrieve/pii/S1673852721001910 |journal=Journal of Genetics and Genomics |volume=48 |issue=11 |pages=984–993 |doi=10.1016/j.jgg.2021.06.007 |pmid=34393089 |s2cid=237094069 |url-access=subscription }}</ref> 

Further along the auditory pathway, the movement of the basilar membrane results in the stimulation of primary auditory neurons. Many of these neurons are specifically "tuned" (respond most strongly) to the narrow frequency range of returning echoes of CF calls. Because of the large size of the acoustic fovea, the number of neurons responding to this region, and thus to the echo frequency, is especially high.<ref name="Carew_2001">{{cite book |last=Carew |first=T. |date=2004 |orig-year=2001 |title=Behavioral Neurobiology: The Cellular Organization of Natural Behavior |publisher=Oxford University Press |isbn=978-0-8789-3084-5 |chapter=<!--Part II: Sensory Worlds: -->Echolocation in Bats}}</ref>