Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Echolocation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources
PubMed1998

Echolocation range of captive and free-ranging baiji (Lipotes vexillifer), finless porpoise (Neophocaena phocaenoides), and bottlenose dolphin (Tursiops truncatus).

The interclick intervals of captive dolphins are known to be longer than the two-way transit time between the dolphin and a target. In the present study, the interclick intervals of free-ranging baiji, finless porpoises, and bottlenose dolphins in the wild and in captivity were compared. The click intervals in open waters ranged up to 100-200 ms, whereas the click intervals in captivity were in the order of 4-28 ms. Echolocation of free-ranging dolphins appears to adapt to various distance in navigation or ranging, sometimes up to 140 m. Additionally, the difference of waveform characteristics of clicks between species was recognized in the frequency of maximum energy and the click duration.

Animals↗
PubMed1976

Coordinated activities of middle-ear and laryngeal muscles in echolocating bats.

The middle-ear muscles and laryngeal muscles of the little brown bat (Myotis lucifugus) are highly developed. When the bat emits orientation sounds, action potentials of middle-ear muscles appear approximately 3 milliseconds after those of the laryngeal muscles; this activity of middle-ear muscles attenuates the vocal self-stimulation and improves the performance of the echolocation system. When an acoustic stimulus is delivered, both types of muscles contract; action potentials of the laryngeal muscles appear approximately 3 milliseconds after those of the middle-ear muscles. These two groups of muscles are apparently activated in a coordinated manner not only by the nerve impulses from the vocalization center, but also by those from the auditory system.

Action Potentials↗
PubMed1972

Neural attenuation of responses to emitted sounds in echolocating rats.

Bats of the family Vespertilionidae enmit strong ultrasonic pulses for echolocation. If such sounds directly stimulate their ears, the detection of echoes from short distances would be impaired. The responses of lateral lemniscal neurons to emitted sounds were found to be much smaller than those to playback sounds, even when the response of the auditory nerve was the same to both types of sounds. Thus, responses to self-vocalized sounds were attenuated between the cochlear nerve and the inferior colliculus. The mean attenuation was 25 decibels. This neural attenuating mechanism is probably a part of the mechanisms for effective echo detection.

Animals↗
PubMed1974

Site of neural attenuation of responses to self-vocalized sounds in echolocating bats.

Bats of the genus Myotis emit intense orientation sounds for echolocation. If such sounds directly stimulated their ears, the detection of echoes from short distances would be impaired. In addition to the muscular mechanism in the middle ear, the bat has a neural mechanism in the brain for attenuation of responses to self-vocalized orientation and nonorientation sounds. This neural attenuating mechanism operates in the nucleus of the lateral lemniscus, reducing its activity by about 15 decibels, and it is synchronized with vocalization.

Acoustic Stimulation↗
PubMed1974

Target structure and echo spectral discrimination by echolocating bats.

Echolocating bats can use sonar to discriminate among targets which reflect echoes differing in spectral distribution of energy but not in overall intensity. They can detect differences smaller than 1 millimeter in fine target structure. Bats may be capable of classifying targets from echo spectral signatures and might thus be able to distinguish among flying insect prey by sonar.

Animals↗
PubMed1979

The oilbird: hearing and echolocation.

Oilbirds can navigate in total darkness by echolocation. The sound energy in their sonar cries is unevenly distributed over the range from about 1 to 15 kilohertz, with a dominant frequency range of 1.5 to 2.5 kilohertz. This corresponds to the most sensitive range of their hearing as determined by neurophysiological methods. Behavioral tests in their home cave indicate that the smallest object avoided by this is a disk 20 centimeters in diameter.

Animals↗
PubMed1984

Neural mechanisms of sound localization in an echolocating bat.

The mustache bat emits a three-harmonic echolocation pulse. At the external ear, large interaural intensity differences are generated only when a sound originates within a limited area of two-dimensional space, and this area is different for each pulse harmonic. As a consequence, the external ear generates pronounced binaural spectral cues containing two-dimensional spatial information. This information is encoded in the inferior colliculus by neurons tuned to one of the harmonics and sensitive to interaural intensity differences.

Acoustics↗
PubMed1982

Echolocation in bats: the external ear and perception of the vertical positions of targets.

Echolocating bats (Eptesicus fuscus) can perceive changes of as little as 3 degrees of arc in the vertical angles separating pairs of horizontal rods. This acuity depends upon modification of sounds entering the external ear canal by the structures of the external ear. Deflection of the tragus degrades the acuity of vertical-angle perception from 3 degrees to about 12 degrees to 14 degrees. The pinna-tragus structure produces a strong secondary echo of sounds entering the external ear canal, and the delay of this echo after the time when the sound directly enters the ear canal apparently encodes the vertical direction of a sound source.

Animals↗
PubMed1982

Neural representation of target distance in auditory cortex of the echolocating bat Myotis lucifugus.

1. Single- and multiunit recordings were obtained from neurons in the auditory cortex of the echolocating bat Myotis lucifugus, while trains of stimuli designed to simulate the bat's frequency-modulated (FM) orientation pulse and its returning echo were delivered. It was found that many neurons in the cortex responded selectively to pulse-echo pairs only if the time delay separating the artificial pulse and the echo was within a certain range. This response property is called "delay-dependent facilitation." Since echolating bats are known to utilize echo-delay information for the determination of target distance, it is postulated that these neurons are involved in the process of distance perception. 2. Two types of delay-sensitive neurons were characterized on the basis of their response patterns. P-type units had short maximum response delays, narrow delay response functions, and response latencies for pulse-echo pairs that were similar to their response latencies for single loud FM pulses. E-type units had longer maximum response delays, wide delay response functions, and pulse-echo pair response latencies that were time-locked to the echo. Another important difference between these two classes was that changes in the amplitude of the artificial echo caused systematic changes in the delay response of E-type units but not of P-type units. 3. The sharpness and stability of the delay response functions of P-type units suggested that they may encode target distance by responding at discrete echo delays. In contrast, delay tuning may not be an unambiguous determinant of echo delay in E-type units. Here, the most consistent and reliable response parameter for echo delay is the time at which the responses occurred. This suggested that echo delay could be encoded by the temporal pattern of responses in E-type units in relation to the responses evoked by the outgoing orientation cry. The different range of delay of delay sensitivity of P-type and E-type units indicates that these two mechanisms could be operating at different ranges of target distance. 4. P-type and E-type responses may not be due to different populations of neurons but to different response properties of the same population under different conditions. Evidence for this proposition was obtained by showing that in some recordings, decreases in the amplitude of the artificial pulse caused a switch in response from a long best delay, E-type response to a short best delay, P-type response. This suggested that the delay sensitivity of cortical neurons could be under the bat's control based on the intensity of its pulse emissions.

Animals↗
PubMed1985

Interaural time and intensity coding in superior olivary complex and inferior colliculus of the echolocating bat Molossus ater.

Single-unit responses to tonal stimulation with interaural disparities were recorded in the nuclei of the superior olivary complex (SOC) and the central nucleus of the inferior colliculus (ICC) of the echolocating bat, Molossus ater. Seventy-six units were recorded from the ICC and 74 from the SOC; of the SOC units, 31 were histologically verified in the medial superior olive (MSO), 10 in the lateral superior olive (LSO), and 33 in unidentified areas of the SOC. Best frequencies (BFs) of the units ranged from 10.3 to 89.6 kHz, and Q10 dB values ranged from 2 to 70 dB. Most ICC neurons responded phasically to stimulus onset and were either inhibitory/excitatory [I/E; (53)] or excitatory/excitatory [E/E; (21)] units. In the MSO, 23 units responded tonically and 7 phasically on, 18 were E/E or E/OF (facilitatory for other input) units, and 11 were I/E neurons. All LSO neurons responded in a "chopper" fashion, and the binaural neurons were E/I units. In E/E units the excitatory response to binaural stimulation was frequently larger than the sum of the monaurally evoked responses. Many neurons with E/I or I/E inputs had very steep binaural impulse-count functions and were sensitive to small interaural intensity differences. Twenty-eight units (24%) responded with a change in firing rate of at least 20% to interaural time differences of +/- 500 microseconds. Within this sample, 11 units (8 from ICC, 2 from MSO, and 1 from SOC) were sensitive to interaural time differences of only +/- 50 microseconds. Of these 11 units, 10 were I/E units responding phasically only to stimulus onset and were also sensitive to intensity differences (delta I), being suppressed completely by the inhibitory input over a delta I range of 20 dB or less. Of 117 units tested in the ICC and SOC nuclei, 86 units (76%) were not sensitive to interaural time disparities within +/- 500 microseconds. Because the BFs of these units sensitive to interaural transient time differences (delta t) ranged between 18 and 90 kHz, responses were elicited by pure tones, and responses did not change periodically with the period equal to that of the stimulus frequency, we conclude that the neurons reacted to interaural differences of stimulus-onset time (transient time difference) but not to phase differences (ongoing time difference). Sensitivity to interaural time differences was also correlated with interaural intensity differences.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Response properties of single units in the dorsal nucleus of the lateral lemniscus and paralemniscal zone of an echolocating bat.

1. Connectional evidence suggests that the dorsal nucleus of the lateral lemniscus (DNLL) and the paralemniscal zone (PL) function as centers for binaural analysis interposed between the superior olivary complex and the midbrain. In addition, the DNLL is known to be a major source of inhibitory input to the midbrain. The aim of this study was to characterize the response properties of neurons in DNLL and PL of the echolocating bat Eptesicus fuscus, a species that utilizes high-frequency hearing and that might be expected to have a large proportion of neurons responsive to interaural differences in sound level. 2. Auditory stimuli were presented monaurally or binaurally to awake animals, and responses of single units were recorded extra-cellularly with the use of glass micropipettes. 3. Below the ventrolateral border of the inferior colliculus is a region that contains large gamma-aminobutyric acid-positive neurons. On the basis of its immunohistochemical reactivity, this entire region could be considered as DNLL. However, within the area, there was an uneven distribution of binaural responses. Caudally, binaural neurons made up 84% (41/49) of those tested, but rostrally only 29% (6/21). For this reason the rostral area is considered as a separate functional subdivision and referred to as the dorsal paralemniscal zone (DPL). PL is located ventral to DPL and medial to the intermediate and ventral nuclei of the lateral lemniscus; in PL 88% (14/16) of neurons were binaural. 4. Most neurons responded only to a contralateral stimulus when sounds were presented monaurally. Out of 49 neurons in DNLL, 42 responded only to a contralateral sound, 1 responded only to an ipsilateral sound, and 6 responded to sound at either ear. In the DPL, all of the 21 neurons tested responded to a contralateral sound and none to an ipsilateral sound. Out of 16 neurons in the PL, 11 responded only to a contralateral sound, 1 responded only to an ipsilateral sound, and 4 responded to sound at either ear. 5. When sounds were presented at both ears simultaneously, several different patterns of binaural interaction occurred. The most common pattern was suppression of the response to sound at one ear by sound at the other ear. In DNLL, 57% (28/49) of neurons showed this type of binaural interaction. Another 10% (5/49) showed facilitation at some interaural level differences and suppression at others, and another 10% (5/49) showed facilitation at some interaural level differences but no suppression.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2000

Neural responses to overlapping FM sounds in the inferior colliculus of echolocating bats.

The big brown bat, Eptesicus fuscus, navigates and hunts prey with echolocation, a modality that uses the temporal and spectral differences between vocalizations and echoes from objects to build spatial images. Closely spaced surfaces ("glints") return overlapping echoes if two echoes return within the integration time of the cochlea ( approximately 300-400 micros). The overlap results in spectral interference that provides information about target structure or texture. Previous studies have shown that two acoustic events separated in time by less than approximately 500 micros evoke only a single response from neural elements in the auditory brain stem. How does the auditory system encode multiple echoes in time when only a single response is available? We presented paired FM stimuli with delay separations from 0 to 24 micros to big brown bats and recorded local field potentials (LFPs) and single-unit responses from the inferior colliculus (IC). These stimuli have one or two interference notches positioned in their spectrum as a function of two-glint separation. For the majority of single units, response counts decreased for two-glint separations when the resulting FM signal had a spectral notch positioned at the cell's best frequency (BF). The smallest two-glint separation that reliably evoked a decrease in spike count was 6 micros. In addition, first-spike latency increased for two-glint stimuli with notches positioned nearby BF. The N(4) potential of averaged LFPs showed a decrease in amplitude for two-glint separations that had a spectral notch near the BF of the recording site. Derived LFPs were computed by subtracting a common-mode signal from each LFP evoked by the two-glint FM stimuli. The derived LFP records show clear changes in both the amplitude and latency as a function of two-glint separation. These observations in relation with the single-unit data suggest that both response amplitude and latency can carry information about two-glint separation in the auditory system of E. fuscus.

Acoustic Stimulation↗
PubMed1986

Processing of acoustic temporal patterns in barn owls and echolocating bats: similar mechanisms for the generation of neural place representations of auditory space.

Evidence for 'coincidence detection' or temporal summation mechanisms of temporal-pattern processing is presented for interaural-phase comparison in the barn owl's brainstem and echo delay sensitivity in the auditory cortex of the echolocating bat Myotis lucifugus. In each system, temporal tuning is correlated with the synchronous arrival of excitatory inputs from different acoustic events. Input coincidence is achieved by differences in neural transmission delay that counterbalance acoustic time disparities. Neural transmission delays are spatially organized, thus producing a topographic representation of acoustic time disparity.

Animals↗
PubMed2006

'Binaural echo disparity' as a potential indicator of object orientation and cue for object recognition in echolocating nectar-feeding bats.

Echolocating bats emit ultrasonic calls through their mouth or their nostrils and receive echoes from objects with both their ears. Information conveyed in the echoes is the basis for their three-dimensional acoustic perception of the surroundings. The direction of an object is encoded in binaural echo differences, i.e. on the one hand in the different arrival times of its echo at the two ears, and on the other hand in spectral differences through direction-dependent frequency filtering of head and pinnae. Insufficient attention has been paid, however, to the fact that three-dimensional objects produce structured spatial echo fields, and that the position of the ear in this field determines the echo it receives. We were interested to determine whether the two ears, in addition to direction-specific echo differences, receive object-specific echo disparities that might be useful for the bat. Our measurements with an artificial bat head, which consisted of two microphones and a small ultrasound loudspeaker arranged to resemble a bat's ears and mouth, revealed that echoes at the two ears differed largely depending on the shape and orientation of the echo-giving object. Binaural echo disparities of a bat-pollinated flower did indeed carry information about the orientation and, to a lesser extent, the shape of the flower. During flower approach such object-specific binaural echo disparities even exceed the binaural differences encoding direction of echo incidence, because the echo from the flower in front undergoes the same directional filtering by the two symmetrical ears. Nectar-feeding bats could use these object-specific binaural echo disparities not only to determine the object's orientation relative to the approaching bat, facilitating flight planning, but also to improve object recognition through spatial reconstruction of details of the object creating the echo. Our results suggest that the evaluation of binaural echo disparity has a greater importance for these tasks than has previously been assumed.

Animals↗
PubMed2006

Size discrimination of hollow hemispheres by echolocation in a nectar feeding bat.

Nectar feeding bats use echolocation to find their flowers in the dense growth of tropical rainforests, and such flowers have evolved acoustic features that make their echo more conspicuous to their pollinators. To shed light on the sensory and cognitive basis of echoacoustic object recognition we conducted a size discrimination experiment with the nectarivorous bat Glossophaga soricina and compared the bats' behavioural performance with the echoic features of the training objects. We chose a simple geometric form, the hollow hemisphere, as the training object because of its resemblance to the bell-shaped concave form of many bat flowers, as well as its special acoustic qualities. The hemispheres showed a characteristic echo pattern, which was constant over a wide range of angles of sound incidence. We found systematic size-dependent changes in the echo's temporal and spectral pattern as well as in amplitude. Bats were simultaneously confronted with seven different sizes of hollow hemispheres presented from their concave sides. Visits to one particular size were rewarded with sugar water, while we recorded the frequency of visits to the unrewarded hemispheres. We found that: (1) bats learned to discriminate between hemispheres of different size with ease; (2) the minimum size difference for discrimination was a constant percentage of the hemisphere's size (Weber fraction: approximately 16% of the radius); (3) the comparison of behavioural data and impulse response measurements of the objects' echoes yielded discrimination thresholds for mean intensity differences (1.3 dB), the temporal pattern (3-22 micros) and the change of spectral notch frequency (approximately 16%). We discuss the advantages of discrimination in the frequency and/or time domain.

Acoustics↗
PubMed2006

Foraging Blainville's beaked whales (Mesoplodon densirostris) produce distinct click types matched to different phases of echolocation.

Blainville's beaked whales (Mesoplodon densirostris Blainville) echolocate for prey during deep foraging dives. Here we use acoustic tags to demonstrate that these whales, in contrast to other toothed whales studied, produce two distinct types of click sounds during different phases in biosonar-based foraging. Search clicks are emitted during foraging dives with inter-click intervals typically between 0.2 and 0.4 s. They have the distinctive form of an FM upsweep (modulation rate of about 110 kHz ms(-1)) with a -10 dB bandwidth from 26 to 51 kHz and a pulse length of 270 micros, somewhat similar to chirp signals in bats and Cuvier's beaked whales (Ziphius cavirostris Cuvier), but quite different from clicks of other toothed whales studied. In comparison, the buzz clicks, produced in short bursts during the final stage of prey capture, are short (105 micros) transients with no FM structure and a -10 dB bandwidth from 25 to 80 kHz or higher. Buzz clicks have properties similar to clicks reported from large delphinids and hold the potential for higher temporal resolution than the FM clicks. It is suggested that the two click types are adapted to the separate problems of target detection and classification versus capture of low target strength prey in a cluttered acoustic environment.

Animals↗
PubMed1975

Peripheral control of acoustic signals in the auditory system of echolocating bats.

Many species of echolocating bats emit intense orientation sounds. If such intense sounds directly stimulated their ears, detection of faint echoes would be impaired. Therefore, possible mechanisms for the attenuation of self-stimulation were studied with Myotis lucifugus. The acoustic middle-ear-muscle reflex could perfectly and transiently regulate the amplitude of an incoming signal only at its beginning. However, its shortest latency in terms of electromyograms and of the attenuation of the cochlear microphonic was 3-4 and 4-8 msec, respectively, so that these muscles failed to attenuate orientation signals by the reflex. The muscles, however, received a message from the vocalization system when the bat vocalized, and contracted synchronously with vocalization. The duration of the contraction-relaxation was so short that the self-stimulation was attenuated, but the echoes were not. The tetanus-fusion frequency of tha stapedium muscle ranged between 260 and 320/sec. Unlike the efferent fibres in the lateral-line and vestibular systems, the olivo-cochlear bundle showed no sign of attenuation of self-stimulation.

Acoustic Stimulation↗
PubMed2006

Geographical variation in echolocation call and body size of the Okinawan least horseshoe bat, Rhinolophus pumilus (Mammalia: Rhinolophidae), on Okinawa-jima Island, Ryukyu Archipelago, Japan.

The Okinawan least horseshoe bat, Rhinolophus pumilus, is a cave-dwelling species endemic to the central and southern Ryukyus, Japan. We analyzed variation in the constant frequency (CF) of the echolocation call and in forearm length (FAL) of this species on Okinawa-jima Island on the basis of data for 479 individuals from 11 caves scattered over the island. CF values in samples from six caves, all located in the southwestern half of Okinawa-jima, were significantly higher than those in samples from five caves in the northeastern half of the island. Also, FAL was significantly greater in the latter group than in the former group, although the ranges of variation in this character substantially overlapped between the two groups. These results suggest substantial differentiation between R. pumilus populations on Okinawa-jima. The implications of our findings for the conservation of this endangered bat species are briefly discussed.

Animals↗