Foraging behaviour and echolocation in the rufous horseshoe bat (Rhinolophus rouxi) of Sri Lanka

Neuweiler, Gerhard; Metzner, Walter; Heilmann, Ute; Rübsamen, Rudolf; Eckrich, Michael J.; Costa, H.H.

doi:10.1007/bf00292166

Cited by 175 publications

(162 citation statements)

References 26 publications

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“…A typical horseshoe bat call is depicted in Figure 4a. It usually begins with a brief upward frequency modulation, followed by the characteristic long constant-frequency component, and terminates with a short downward frequency-modulated portion (Schnitzler, 1968;Neuweiler et al, 1987). Injection of MUS (Fig.…”

Section: Effects Of Gabaergic Drugsmentioning

confidence: 99%

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A Neural Basis for Auditory Feedback Control of Vocal Pitch

2003

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Hearing one's own voice is essential for the production of correct vocalization patterns in many birds and mammals, including humans. Bats, for instance, adjust temporal, spectral, and intensity parameters of their echolocation calls by precisely monitoring the characteristics of the returning echo signals. However, neuronal substrates and mechanisms for auditory feedback control of vocalizations are still mostly unknown in any vertebrate. We used echolocating horseshoe bats to investigate the role of the midbrain and hindbrain tegmentum for the control of call frequencies in response to changing auditory feedback. These bats accurately control the frequency of their echolocation calls through auditory feedback both when the bat is at rest [resting frequency (RF)] and when it is flying and compensating for changes in echo frequency caused by flight-induced Doppler shifts [Doppler shift compensation (DSC)]. We iontophoretically injected various GABAergic and glutamatergic transmitter agonists and antagonists into the brainstem tegmentum. We found that within the parabrachial nuclei and the immediately adjacent tegmentum, excitatory effects caused by application of the glutamate agonist AMPA or the GABA A antagonist bicuculline raised RF and the frequency of calls emitted during DSC. Bicuculline application routinely blocked DSC altogether. Alternately, inhibitory effects caused by application of either the GABA A agonist muscimol or the AMPA antagonist CNQX lowered call frequencies emitted at rest and during DSC. Such an audio-vocal feedback mechanism might share basic aspects with audio-vocal feedback controlling the pitch of vocalizations in other mammals, including the involuntary response to "pitch-shifted feedback" in humans.

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Section: Effects Of Gabaergic Drugsmentioning

confidence: 99%

“…Their echolocation calls are characterized by the presence of a long constantfrequency component (Schnitzler, 1968;Neuweiler et al, 1987;Konstantinov et al, 1988). The frequency of calls emitted while the bat is perched is called the resting frequency (RF; Schnitzler, 1968).…”

Section: Introductionmentioning

confidence: 99%

A Neural Basis for Auditory Feedback Control of Vocal Pitch

2003

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“…Horseshoe bats are insectivorous bats that hunt for insects in acoustically dense surroundings, scrub jungle and canopy (Neuweiler et al 1987). They encounter different types of interferences from reflections depending on the hunting strategy, i.e.…”

Section: Temporal and Spectral Gating Mechanisms And Clutter Rejectionmentioning

confidence: 99%

“…The Sri Lankan rufous horseshoe bat, Rhinolophus rouxi, catches flying insects in the jungle on the wing or with a hang-and-wait strategy (Neuweiler et al 1987). While searching for prey the horseshoe bats emit long (20-60 ms) echolocation signals which consist of a pure tone component (CF) of an individual frequency called resting frequency (RF) within a species-specific frequency range of 72-79 kHz.…”

Section: Introductionmentioning

confidence: 99%

Spectral and temporal gating mechanisms enhance the clutter rejection in the echolocating bat, Rhinolophus rouxi

Neumann

Schuller

1991

J Comp Physiol A

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Summary. Doppler shift compensation behaviour in horseshoe bats, Rhinolophus rouxi, was used to test the interference of pure tones and narrow band noise with compensation performance. The distortions in Doppler shift compensation to sinusoidally frequency shifted echoes (modulation frequency: 0.1 Hz, maximum frequency shift: 3 kHz) consisted of a reduced compensation amplitude and/or a shift of the emitted frequency to lower frequencies (Fig. 1).Pure tones at frequencies between 200 and 900 Hz above the bat's resting frequency (RF) disturbed the Doppler shift compensation, with a maximum of interference between 400 and 550 Hz (Fig. 2). Minimum duration of pure tones for interference was 20 ms and durations above 40 ms were most effective (Fig. 3). Interfering pure tones arriving later than about 10 ms after the onset of the echolocation call showed markedly reduced interference (Fig. 4). Doppler shift compensation was affected by pure tones at the optimum interfering frequency with sound pressure levels down to -48 dB rel the intensity level of the emitted call (Figs. 5, 6).Narrow bandwidth noise (bandwidth from + 100 Hz to _ 800 Hz) disturbed Doppler shift compensation at carrier frequencies between -250 Hz below and 800 Hz above RF with a maximum of interference between 250 and 500 Hz above resting frequency (Fig. 7). The duration and delay of the noise had similar influences on interference with Doppler shift compensation as did pure tones (Figs. 8, 9). Intensity dependence for noise interference was more variable than for pure tones (-32 dB to --45 dB rel emitted sound pressure level, Fig. 10).The temporal and spectral gating in Doppler shift compensation behaviour is discussed as an effective mechanism for clutter rejection by improving the processing of frequency and amplitude transients in the echoes of horseshoe bats.Abbreviations: CF constant frequency; FM frequency modulation; RF resting frequency; SPL sound pressure level * To whom offprint requests should be sent

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“…The Lombard effect has been used as a therapeutic tool to improve speech intelligibility in patients suffering from Parkinson's disease, and is also relevant to the study of phonetics and linguistics as well as in the context of animal behavior and the evolution of vocal plasticity (21). Therefore, studying the Lombard effect, the associated vocal changes, and their interaction between each other may lead to a better understanding of both the phenomenology and the underlying neurobiological control mechanisms (23).Echolocating bats are an excellent animal model to study the effects of masking ambient noise on vocal behavior; they are highly vocal and constantly adjust their echolocation pulses to optimize signal detection by monitoring the returning echo signals, which represent the feedback from their own voice (24,25). In addition, the bats' large hearing range of some 100 kHz (26) (Fig.…”

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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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Foraging behaviour and echolocation in the rufous horseshoe bat (Rhinolophus rouxi) of Sri Lanka

Cited by 175 publications

References 26 publications

A Neural Basis for Auditory Feedback Control of Vocal Pitch

A Neural Basis for Auditory Feedback Control of Vocal Pitch

Spectral and temporal gating mechanisms enhance the clutter rejection in the echolocating bat, Rhinolophus rouxi

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

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