Auditory fovea and Doppler shift compensation: adaptations for flutter detection in echolocating bats using CF-FM signals

Schnitzler, Hans‐Ulrich; Denzinger, Annette

doi:10.1007/s00359-010-0569-6

Cited by 131 publications

(180 citation statements)

References 121 publications

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“…These long, narrow-band echolocation signals enable the bats to use echo cues caused by the wing beats of the flying insects upon which they prey. Fluttering insects cause frequency modulations in the returning echoes, which contain the information necessary for the bat to detect and even recognize its prey (27,28).…”

Section: Resultsmentioning

confidence: 99%

“…A filter mechanism that is narrowly tuned to the echo's narrowband frequency component rejects background clutter while it helps to detect acoustic glints. This auditory filter is found in the cochlea, and results in an increased number of receptor cells in the cochlea as well as higher-order auditory neurons that are highly sensitive to the echo pure tone (27,37). Because in the mammalian eye and within the visual central nervous structures the area of the optic fovea is overrepresented in a very similar manner, the auditory filter in horseshoe bats is similarly called an "auditory fovea" (29).…”

Section: Discussionmentioning

confidence: 99%

“…During flight, the dominant CF components of the horseshoe bats' calls are shifted as a result of Doppler effects, and they compensate for these shifts by adjusting the frequency of the subsequent calls (24). This so-called Doppler-shift compensation (DSC) behavior ensures that the echoes remain within the bat's auditory fovea (27,29). Returning echoes also vary in amplitude as a result of varying distances to objects.…”

Section: Discussionmentioning

confidence: 99%

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Ambient noise induces independent shifts in call frequency and amplitude within the Lombard effect in echolocating bats

Hage

Jiang

Berquist

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

126

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The Lombard effect, an involuntary rise in call amplitude in response to masking ambient noise, represents one of the most efficient mechanisms to optimize signal-to-noise ratio. The Lombard effect occurs in birds and mammals, including humans, and is often associated with several other vocal changes, such as call frequency and duration. Most studies, however, have focused on noisedependent changes in call amplitude. It is therefore still largely unknown how the adaptive changes in call amplitude relate to associated vocal changes such as frequency shifts, how the underlying mechanisms are linked, and if auditory feedback from the changing vocal output is needed. Here, we examined the Lombard effect and the associated changes in call frequency in a highly vocal mammal, echolocating horseshoe bats. We analyzed how bandpassfiltered noise (BFN; bandwidth 20 kHz) affected their echolocation behavior when BFN was centered on different frequencies within their hearing range. Call amplitudes increased only when BFN was centered on the dominant frequency component of the bats' calls. In contrast, call frequencies increased for all but one BFN center frequency tested. Both amplitude and frequency rises were extremely fast and occurred in the first call uttered after noise onset, suggesting that no auditory feedback was required. The different effects that varying the BFN center frequency had on amplitude and frequency rises indicate different neural circuits and/or mechanisms underlying these changes.A ny transmission of signals between sender and receiver faces the challenge of being subjected to masking by noise. For acoustic signals, for example, animals have evolved several strategies that aid in increasing the signal-to-noise ratio, thus facilitating signal transmission. One of the most efficient mechanisms is the socalled Lombard effect, i.e., the involuntary rise in call amplitude in response to masking ambient noise (1). This effect was first described in human communication a century ago (2) and has since been found in several species of birds (3-11) and various mammals (12-17), including bats (18). In human speech, several vocal changes, such as a rise in fundamental frequency (19) or lengthening in word duration (20), are often accompanied with the Lombard effect; combined, these changes are referred to as Lombard speech (21). Vocal changes associated with the Lombard effect have rarely been analyzed in animal species. So far, noisedependent changes in call frequency have been observed in birds (8,11,22), and changes in call duration in birds and monkeys (8,12).Most animal studies, however, have focused on noise-dependent changes in call amplitude and do not examine other possible vocal changes (2-5, 7, 9, 10, 15-17). It is therefore still largely unknown how the adaptive changes in call amplitude relate to frequency shifts or call elongation and how the underlying mechanisms are linked. It is also unknown if auditory feedback from the changing vocal output is needed to drive the Lombard effect in general.Over...

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Ambient noise induces independent shifts in call frequency and amplitude within the Lombard effect in echolocating bats

Hage

Jiang

Berquist

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

126

View full text Add to dashboard Cite

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“…the CF of the second harmonic of the echo-locating signal, are highly overrepresented [35,52,60], as well as Doppler shift compensation (DSC) that maintain the CF component of echoes within the sensitive auditory fovea [118,119]. Behavioral studies have showed that mustached bats and some horseshoe bats are adept at attacking fluttering targets [120,121], which induce the echo to generate frequency and amplitude shifts called glints [117,122], but the echo duration does not change and becomes a "tag" recognizing the echo from the target [61].…”

Section: Translational Neurosciencementioning

confidence: 99%

The function of offset neurons in auditory information processing

Xu¹,

Fu²,

Chen³

2014

Translational Neuroscience

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Offset neurons which respond to the termination of the sound stimulation may play important roles in auditory temporal information processing, sound signal recognition, and complex distinction. Two additional possible mechanisms were reviewed: neural inhibition and the intrinsic conductance property of offset neuron membranes. The underlying offset response was postulated to be located in the superior paraolivary nucleus of mice. The biological significance of the offset neurons was discussed as well.

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“…For the first paper of this section, Schnitzler and Denzinger (2011), as already mentioned above, reviewed the discovery and investigation of the auditory fovea and of Doppler shift compensation. Borina et al (2011) found a population of auditory midbrain neurons that are sensitive to interaural time differences of the echo envelope and suggest that, in addition to interaural intensity differences, interaural time differences are used for object location by echolocating bats.…”

mentioning

confidence: 99%