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  • 1
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    Frontiers Media SA
    Publication Date: 2024-03-31
    Description: Echolocation has evolved in different groups of animals, from bats and cetaceans to birds and humans, and enables localization and tracking of objects in a dynamic environment, where light levels may be very low or absent. Nature has shaped echolocation, an active sense that engages audiomotor feedback systems, which operates in diverse environments and situations. Echolocation production and perception vary across species, and signals are often adapted to the environment and task. In the last several decades, researchers have been studying the echolocation behavior of animals, both in the air and underwater, using different methodologies and perspectives. The result of these studies has led to rich knowledge on sound production mechanisms, directionality of the sound beam, signal design, echo reception and perception. Active control over echolocation signal production and the mechanisms for echo processing ultimately provide animals with an echoic scene or image of their surroundings. Sonar signal features directly influence the information available for the echolocating animal to perceive images of its environment. In many echolocating animals, the information processed through echoes elicits a reaction in motor systems, including adjustments in subsequent echolocation signals. We are interested in understanding how echolocating animals deal with different environments (e.g. clutter, light levels), tasks, distance to targets or objects, different prey types or other food sources, presence of conspecifics or certain predators, ambient and anthropogenic noise. In recent years, some researchers have presented new data on the origins of echolocation, which can provide a hint of its evolution. Theoreticians have addressed several issues that bear on echolocation systems, such as frequency or time resolution, target localization and beam-forming mechanisms. In this Research Topic we compiled recent work that elucidates how echolocation – from sound production, through echolocation signals to perception- has been shaped by nature functioning in different environments and situations. We strongly encouraged comparative approaches that would deepen our understanding of the processes comprising this active sense.
    Keywords: QP1-981 ; Q1-390 ; bats ; Biosonar ; Humans ; marine mammals ; sensory biology ; Birds ; Behavior ; Communication ; thema EDItEUR::M Medicine and Nursing::MF Pre-clinical medicine: basic sciences::MFG Physiology
    Language: English
    Format: image/jpeg
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  • 2
    Publication Date: 2017-10-11
    Description: Many species of bat emit acoustic signals and use information carried by echoes reflecting from nearby objects to navigate and forage. It is widely documented that echolocating bats adjust the features of sonar calls in response to echo feedback; however, it remains unknown whether audiovocal feedback contributes to sonar call...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 3
    Publication Date: 2017-06-21
    Description: Sensing is fundamental to the control of movement: From grasping objects to speech production, sensing guides action. So far, most of our knowledge about sensorimotor integration comes from visually guided reaching and oculomotor integration, in which the time course and trajectories of movements can be measured at a high temporal...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 4
    ISSN: 1432-1351
    Keywords: Echolocation ; Biosonar ; Auditory system ; Acoustic images ; Neural timing ; Target ranging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Behavioral experiments with jittering echoes examined acoustic images of sonar targets in the echolocating bat, Eptesicus fuscus, along the echo delay or target range axis. Echo phase, amplitude, bandwidth, and signal-to-noise ratio were manipulated to assess the underlying auditory processes for image formation. 2. Fine delay acuity is about 10 ns. Calibration and control procedures indicate that this represents temporal acuity rather than spectral discrimination. Jitter discrimination curves change in phase when the phase of one jittering echo is shifted by 180° relative to the other, showing that echo phase is involved in delay estimation. At an echo detectability index of about 36 dB, fine acuity is 40 ns, which is approximately as predicted for the delay accuracy of an ideal receiver. 3. Compound performance curves for 0° and 180° phase conditions match the crosscorrelation function of the echoes. The locations of both 0° and 180° phase peaks in the performance curves shift along the time axis by an amount that matches neural amplitude-latency trading in Eptesicus, confirming a temporal basis for jitter discrimination.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 159 (1986), S. 257-266 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Frequency selectivity of hearing was measured in the green treefrog,Hyla cinerea. A psychophysical technique based on reflex modification was used to obtain masked threshold estimates for pure tones (300–5,400 Hz) presented against two levels of broadband masking noise. A pure tone (S-1) presented 200 ms prior to a reflex-eliciting stimulus (S-2) inhibited the motor reflex response to S-2. The magnitude of this reflex modification effect varied systematically with the sound pressure level (SPL) of S-1, and threshold was defined as the SPL of S-1 at which the reflex modification effect disappeared. 2. Masked thresholds were used to calculate critical ratios, an index of the auditory system's frequency selectivity. The frequency selectivity of the treefrog's hearing is greatest and critical ratios are lowest (22–24 dB) at about 900 and 3,000 Hz, the two spectral regions dominant in the male treefrog's species-specific advertisement call. These results suggest that the treefrog's auditory system may be specialized to reject noise at biologically relevant frequencies. 3. As in other vertebrates, critical ratios remain constant when background noise level is varied; however, the shape of the treefrog's critical ratio function across frequencies differs from the typical vertebrate function that increases with increasing frequency at a slope of about 3 dB/octave. Instead, the treefrog's critical ratio function resembles its pure tone audiogram. Although the shape of the treefrog's critical ratio function is atypical, the critical ratio values themselves are comparable to those of many other vertebrates in the same frequency range. 4. Critical ratio values here measured behaviorally do not match critical ratio values previously measured physiologically in single eighth nerve fibers. This suggests that frequency selectivity of hearing in the green treefrog is mediated in the central, rather than the peripheral, auditory system and probably does not arise directly from the tuning of the individual auditory nerve fibers.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 165 (1989), S. 383-393 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Echolocating bats use the time delay between emitted sounds and returning echoes to determine the distance to an object. This study examined the accuracy of target ranging by bats and the effect of echo bandwidth on the bat's performance in a ranging task. 2. Six big brown bats (Eptesicus fuscus) were trained in a yes-no procedure to discriminate between two phantom targets, one simulating a stationary target that reflected echoes at a fixed delay and another simulating a jittering target that reflected echoes undergoing small step-changes in delay. 3. Eptesicus fuscus emits a frequency modulated sonar sound whose first harmonic sweeps from approximately 55 to 25 kHz in about 2 ms. Sound energy is also present in the second and third harmonics, contributing to a broadband signal in which each frequency in the sound can provide a time marker for its arrival at the bat's ears. We estimated range jitter discrimination in bats under conditions in which the echo information available to the bat was manipulated. Baseline performance with unfiltered echoes was compared to that with filtered echoes (low-pass filtered at 55 kHz and at 40 kHz; high-pass filtered at 40 kHz). 4. The results indicate that the low-frequency portion of the first harmonic (25–40 kHz) is sufficient for the bat to discriminate echo delay changes of 0.4 microseconds. This echo delay discrimination corresponds to a distance discrimination of less than 0.07 mm.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1351
    Keywords: Echolocation ; Bat sonar ; Target ranging ; Acoustic images ; Auditory processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. FM echolocating bats (Eptesicus fuscus) were trained to discriminate between a two-component complex target and a one-component simple target simulated by electronically-returned echoes in a series of experiments that explore the composition of the image of the two-component target. In Experiment I, echoes for each target were presented sequentially, and the bats had to compare a stored image of one target with that of the other. The bats made errors when the range of the simple target corresponded to the range of either glint in the complex target, indicating that some trace of the parts of one image interfered with perception of the other image. In Experiment II, echoes were presented simultaneously as well as sequentially, permitting direct masking of echoes from one target to the other. Changes in echo amplitude produced shifts in apparent range whose pattern depended upon the mode of echo presentation. 2. Eptesicus perceives images of complex sonar targets that explicitly represent the location and spacing of discrete glints located at different ranges. The bat perceives the target's structure in terms of its range profile along a psychological range axis using a combination of echo delay and echo spectral representations that together resemble a spectrogram of the FM echoes. The image itself is expressed entirely along a range scale that is defined with reference to echo delay. Spectral information contributes to the image by providing estimates of the range separation of glints, but it is transformed into these estimates. 3. Perceived absolute range is encoded by the timing of neural discharges and is vulnerable to shifts caused by neural amplitude-latency trading, which was estimated at 13 to 18 μs per dB from N 1 and N 4 auditory evoked potentials in Eptesicus. Spectral cues representing the separation of glints within the target are transformed into estimates of delay separations before being incorporated into the image. However, because they are encoded by neural frequency tuning rather than the time-of-occurrence of neural discharges, the perceived range separation of glints in images is not vulnerable to amplitudelatency shifts. 4. The bat perceives an image that is displayed in the domain of time or range. The image receives no evident spectral contribution beyond what is transformed into delay estimates. Although the initial auditory representation of FM echoes is spectrogram-like, the time, frequency, and amplitude dimensions of the spectrogram appear to be compressed into an image that has only time and amplitude dimensions. The spectral information is not lost but manifests itself as equivalent time-domain information.
    Type of Medium: Electronic Resource
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  • 8
    Publication Date: 2016-02-16
    Description: This study investigated auditory stimulus selectivity in the midbrain superior colliculus (SC) of the echolocating bat, an animal that relies on hearing to guide its orienting behaviors. Multichannel, single-unit recordings were taken across laminae of the midbrain SC of the awake, passively listening big brown bat, Eptesicus fuscus. Species-specific frequency-modulated (FM) echolocation sound sequences with dynamic spectrotemporal features served as acoustic stimuli along with artificial sound sequences matched in bandwidth, amplitude, and duration but differing in spectrotemporal structure. Neurons in dorsal sensory regions of the bat SC responded selectively to elements within the FM sound sequences, whereas neurons in ventral sensorimotor regions showed broad response profiles to natural and artificial stimuli. Moreover, a generalized linear model (GLM) constructed on responses in the dorsal SC to artificial linear FM stimuli failed to predict responses to natural sounds and vice versa, but the GLM produced accurate response predictions in ventral SC neurons. This result suggests that auditory selectivity in the dorsal extent of the bat SC arises through nonlinear mechanisms, which extract species-specific sensory information. Importantly, auditory selectivity appeared only in responses to stimuli containing the natural statistics of acoustic signals used by the bat for spatial orientation—sonar vocalizations—offering support for the hypothesis that sensory selectivity enables rapid species-specific orienting behaviors. The results of this study are the first, to our knowledge, to show auditory spectrotemporal selectivity to natural stimuli in SC neurons and serve to inform a more general understanding of mechanisms guiding sensory selectivity for natural, goal-directed orienting behaviors.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 9
    Publication Date: 2017-06-05
    Description: Sensing is fundamental to the control of movement: From grasping objects to speech production, sensing guides action. So far, most of our knowledge about sensorimotor integration comes from visually guided reaching and oculomotor integration, in which the time course and trajectories of movements can be measured at a high temporal resolution. By contrast, production of vocalizations by humans and animals involves complex and variable actions, and each syllable often lasts a few hundreds of milliseconds, making it difficult to infer underlying neural processes. Here, we measured and modeled the transfer of sensory information into motor commands for vocal amplitude control in response to background noise, also known as the Lombard effect. We exploited the brief vocalizations of echolocating bats to trace the time course of the Lombard effect on a millisecond time scale. Empirical studies revealed that the Lombard effect features a response latency of a mere 30 ms and provided the foundation for the quantitative audiomotor model of the Lombard effect. We show that the Lombard effect operates by continuously integrating the sound pressure level of background noise through temporal summation to guide the extremely rapid vocal-motor adjustments. These findings can now be extended to models and measures of audiomotor integration in other animals, including humans.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 10
    Publication Date: 2017-09-25
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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