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At least 1,711 records · Page 95Linked to original sources
PubMed1991

Facilitation and Delay Sensitivity of Auditory Cortex Neurons in CF - FM Bats, Rhinolophus rouxi and Pteronotus p.parnellii.

Responses of auditory neurons to complex stimuli were recorded in the dorsal belt region of the auditory cortex of two taxonomically unrelated bat species, Rhinolophus rouxi and Pteronotus parnellii parnellii, both showing Doppler shift compensation behaviour. As in P.p.parnellii (Suga et al., J. Neurophysiol., 49, 1573 - 1626, 1983), cortical neurons of R.rouxi show facilitated responses to pairs of pure tones or frequency modulations. Best frequencies for the two components lie near the first and second harmonic of the echolocation call but are in most cases not harmonically related. Neurons facilitated by pairs of pure tones show little dependence on the delay between the stimuli, whereas pairs of frequency modulations evoke best facilitated responses at distinct best delays between 1 and 10 ms. Facilitated neurons are found in distinct portions of the dorsal cortical belt region, with a segregation of facilitated neurons responding to pure tones and to frequency modulations. Non-facilitated neurons are found throughout the field. Neurons are topographically aligned with increasing best delays along a rostrocaudal axis. The best delays between 2 and 4 ms are largely overrepresented numerically, and occupy approximately 56% of the cortical area containing facilitated neurons. A functional interpretation of the large overrepresentation of best delays approximately 3 ms is proposed. Facilitated neurons are located almost entirely within layer V of the dorsal field.

Journal Article↗
PubMed2001

Comparative karyology of Brazilian vampire bats Desmodus rotundus and Diphylla ecaudata (Phyllostomidae, Chiroptera): banding patterns, base-specific fluorochromes and FISH of ribosomal genes.

This paper provides new data on chromosomes of Brazilian vampire bats Desmodus rotundus and Diphylla ecaudata. These species were analyzed by GTG, CBG- and CB-DAPI banding, AgNO3/CMA3 sequential staining, base-specific fluorochrome dyes and in situ hybridization with 18S rDNA probe. C-banding (CBG) revealed constitutive heterochromatin in the pericentromeric regions in all autosomes and the X and Y chromosomes appeared entirely heterochromatic in both species. CB-DAPI revealed a coincident banding pattern to that obtained by CBG. Triple staining CMA3/DA/DAPI revealed an R-banding and a weak G-banding pattern in the karyotypes. Sequential AgNO3/CMA3 staining showed a NOR located interstitially on the long arm of pair 8 in D. rotundus and on the short arm of pair 13 in D. ecaudata. FISH with a rDNA probe confirmed the location and number of NORs; a difference neither in intensity nor in size of hybridization signal was detected between homologues for both species.

Animals↗
PubMed1968

Analysis of frequency-modulated and complex sounds by single auditory neurones of bats.

1. Single unit activity in the inferior colliculus of bats was studied in relation to the analysis of frequency-modulated (FM) and complex sounds. Complex sounds were composed of tone pulse I (pure or FM tone) delivered simultaneously with tone pulse II (pure or sometimes FM tone). It was assumed that in relevant complex sounds produced by animals, an important component (e.g. a formant in human speech) occurred at the best frequency (BF) of a given neurone. Tone pulse I represented such a component (called BF component). Tone pulse II was assumed to correspond to higher or lower components according to its relation to BF. Depending on characteristics of responses to tonal stimuli, collicular neurones were classified into five types: symmetrical, asymmetrical, FM-insensitive, FM-sensitive (or FM-specialized) and upper-threshold units.2. The symmetrical unit had a wide excitatory area and no inhibitory areas and it responded with equal thresholds to FM tone pulses sweeping in either directions. This type of neurone responded to all frequency modulations (e.g. transition in human speech) of the BF component, and the response was scarcely inhibited by other components.3. In the asymmetrical unit, the extent of frequency modulation of the BF component which could excite the neurone was limited by inhibitory areas on one or both sides of an excitatory area. Inhibitory areas on the lower frequency side tended to be larger than those on the high frequency side. The limitation was more severe for frequency sweeps toward the best frequency than for sweeps starting from it. The response to the BF component was inhibited by lower and/or higher components unless these were outside the inhibitory areas. In most of the asymmetrical units, lower components were more important than higher ones in determining whether the response to the BF component could occur.4. In the FM-insensitive unit with a narrow excitatory area, inhibitory areas on both sides of the excitatory area restricted the extent of frequency modulation of the BF components which could activate the neurone. Responses to frequency sweeps toward the best frequency were strongly limited by the inhibitory areas. When the lower and/or higher components were within the inhibitory areas, the response to the BF component was inhibited. This type of neurone responded to more restricted combinations of components than did the asymmetrical units.5. The FM-sensitive unit which had no excitatory area but a large inhibitory area responded only to FM components in a certain range. Evidence was obtained that not only the range and direction but rate and functional form of frequency sweep were important in determining the excitation of the neurone. Noise bursts with various band widths did not activate the neurones. Responses of the neurones were commonly inhibited by tones within an inhibitory area so wide as to involve even frequencies in the FM component which excited the neurone. Thus, the response of the FM-sensitive unit depended not only upon the characteristics of the FM component, but also on the frequencies of other components.6. The asymmetrical, FM-insensitive and FM-sensitive units required for their activation a certain structure in the complex sound. Some of the upper-threshold units did not respond to a sufficiently strong BF component and/or its frequency modulation. Furthermore, the response of the neurone to a weak BF component was inhibited by strong lower and/or higher components in a certain range. Some upper-threshold units also had asymmetrical or FM-sensitive characteristics. Those neurones appeared to be specialized for the analysis of sound structure not only in frequency, but in intensity.7. Although various types of behaviour of single neurones were found in the inferior colliculus, a strong tendency in the neural analysis of complex sound was the restriction of conditions under which single neurones were activated. Neurones at higher levels responded to more restricted sequences or sets of sound stimuli than did those at lower levels.

Action Potentials↗
PubMed1969

Classification of inferior collicular neurones of bats in terms of responses to pure tones, FM sounds and noise bursts.

1. Single unit activity in the inferior colliculus of bats was studied with pure tones, FM (frequency-modulated) sounds and noise bursts which are the most basic three components of the complex sounds produced by many different animals including man. Neurones were divided into three groups, (i) ;generalized' units responding to all three elements, (ii) ;deaf' units responding to two out of the three and (iii) ;specialized' units responding to only one of the three. Each of these was divided into three subgroups.2. Three subgroups of generalized units were called ;symmetrical', ;asymmetrical' and ;upper-threshold' units. The symmetrical unit had a wide excitatory area and responded to any sounds which had components falling in this area. The asymmetrical unit had a narrow excitatory area abutting on a large inhibitory one and showed different responses to FM sounds depending on the directions of frequency sweep. The upper-threshold unit had not only an excitatory area, but also an inhibitory one. The neurone failed to respond to strong sounds, i.e. these showed upper thresholds.3. Three subgroups of deaf units were called ;pure tone-deaf', ;FM-deaf' and ;noise-deaf' units. The pure tone-deaf unit did not respond to any pure tones but did respond to FM sounds and noise bursts. The noise-deaf unit did not respond to noise bursts but did respond to pure and FM tone pulses. An FM-deaf unit has not yet been confirmed.4. Three subgroups of specialized units were called ;pure tone-specialized', ;FM-specialized' and ;noise-specialized' units which responded exclusively to either pure tones, FM sounds or noise bursts, respectively. In the FM- and noise-specialized units, pure tone pulses caused only inhibitory processes.5. About 95% of neurones studied showed phasic on-responses to sound stimuli and almost no spontaneous discharges. Only a small percent of neurones showed spontaneous discharges higher than a few impulses per second. Response patterns of some of these neurones changed with frequency, intensity, duration and repetition rate of sound stimuli. These neurones responded to any of pure tones, FM sounds and noise bursts.6. All neurones except the symmetrical ones had inhibitory areas, in which sounds inhibited responses to excitatory ones when these are delivered simultaneously. Therefore the structure in complex sounds is very important in the excitation of these neurones.

Animals↗
PubMed1971

Responses of inferior collicular neurones of bats to tone bursts with different rise times.

1. A study was made of the responses of single neurones in the inferior colliculus of bats to tone bursts with different rise times (or with different rates of amplitude increase) in order to determine whether the neurones were specialized for analysis of amplitude-modulated sound, especially the rising phase in amplitude.2. The response patterns of neurones which showed phasic on-responses usually did not change with rise time, although the response patterns of some neurones changed from phasic on-responses to inhibitory responses.3. The thresholds of responses to tone bursts increased when the rise time was lengthened. The amount of increase greatly differed from neurone to neurone. For the excitation of neurones which showed a large increase in threshold, the stimulus amplitude should quickly increase in amplitude. For tone bursts with a short rise time, some neurones showed an upper-threshold above which the sounds failed to excite them. The upper-threshold usually disappeared when the rise time was lengthened. For the excitation of neurones which showed an upper-threshold, the rate of amplitude increase and its extent were very important parameters.4. Lengthening the rise time of a tone burst from 0.5 to 98 msec caused various types of change in the excitatory area. In some cases, there was a diminution of the area and, in others, there was an expansion of the area. Neurones showing these changes may be considered to be specialized for responding to tone bursts with either a rapid or slow increase in amplitude.5. Changes with rise time occurred not only in the excitatory area, but also in the inhibitory area. The change in the inhibitory area of a given neurone, however, was not necessarily the same as that in the excitatory area.6. The latency of response usually changed as a function of stimulus amplitude and rise time. In 26% of the neurones studied, however, the latency was relatively constant regardless of stimulus amplitude and rise time. Some of the latency-constant neurones appeared to have properties suited for echo-ranging.7. The changes in excitatory area with rise time appear to involve neural inhibition and/or accommodation. Possible neural mechanisms for the changes in threshold, upper-threshold and response pattern and the properties of latency-constant neurones are discussed.

Animals↗
PubMed2000

Echolocation behavior of big brown bats, Eptesicus fuscus, in the field and the laboratory.

Echolocation signals were recorded from big brown bats, Eptesicus fuscus, flying in the field and the laboratory. In open field areas the interpulse intervals (IPI) of search signals were either around 134 ms or twice that value, 270 ms. At long IPI's the signals were of long duration (14 to 18-20 ms), narrow bandwidth, and low frequency, sweeping down to a minimum frequency (Fmin) of 22-25 kHz. At short IPI's the signals were shorter (6-13 ms), of higher frequency, and broader bandwidth. In wooded areas only short (6-11 ms) relatively broadband search signals were emitted at a higher rate (avg. IPI= 122 ms) with higher Fmin (27-30 kHz). In the laboratory the IPI was even shorter (88 ms), the duration was 3-5 ms, and the Fmin 30- 35 kHz, resembling approach phase signals of field recordings. Excluding terminal phase signals, all signals from all areas showed a negative correlation between signal duration and Fmin, i.e., the shorter the signal, the higher was Fmin. This correlation was reversed in the terminal phase of insect capture sequences, where Fmin decreased with decreasing signal duration. Overall, the signals recorded in the field were longer, with longer IPI's and greater variability in bandwidth than signals recorded in the laboratory.

Animals↗
PubMed2004

A numerical study of the role of the tragus in the big brown bat.

A comprehensive characterization of the spatial sensitivity of an outer ear from a big brown bat (Eptesicus fuscus) has been obtained using numerical methods and visualization techniques. Pinna shape information was acquired through x-ray microtomography. It was used to set up a finite-element model of diffraction from which directivities were predicted by virtue of forward wave-field projections based on a Kirchhoff integral formulation. Digital shape manipulation was used to study the role of the tragus in detailed numerical experiments. The relative position between tragus and pinna aperture was found to control the strength of an extensive asymmetric sidelobe which points in a frequency-dependent direction. An upright tragus position resulted in the strongest sidelobe sensitivity. Using a bootstrap validation paradigm, the results were found to be robust against small perturbations of the finite-element mesh boundaries. Furthermore, it was established that a major aspect of the tragus effect (position dependence) can be studied in a simple shape model, an obliquely truncated horn augmented by a flap representing the tragus. In the simulated wave field around the outer-ear structure, strong correlates of the tragus rotation were identified, which provide a direct link to the underlying physical mechanism.

Animals↗
PubMed1988

Is the structure of bat echolocation calls an adaptation to the mammalian hearing system?

A common feature of most bat echolocation calls is their hyperbolalike frequency modulation. It is proposed that these calls evolved as an adaptation to the filters in the peripheral hearing system. From an analysis of 420 echolocation sounds of Eptesicus fuscus, the bandwidths of filters giving a minimal error of time-delay estimation are predicted; these could be compared to neurophysiological findings.

Adaptation, Physiological↗
PubMed1988

Clutter interference along the target range axis in the echolocating bat, Eptesicus fuscus.

The sensitivity of the echolocating bat, Eptesicus fuscus, for detection of a sonar target is impaired by the presence of additional targets located at similar distances. At a range of 54 cm, sensitivity to one target declines if the range separation to other targets is smaller than 8-9 cm. This loss of sensitivity is an example of clutter interference along the range axis, created by simultaneous masking of one set of echoes by another. Echoes that fall within an experimentally defined critical range band may sum together to contribute collectively to detection in that band. Echoes falling into separate bands may be detected independently. Acoustic glints within a band appear to be grouped together to be perceived as a single range-extended target of complex structure. Range bands may thus define what a "target" is by specifying within-target and between-target differences in range. The width of critical range bands appears to depend upon target range, with wider bands at greater ranges.

Animals↗
PubMed1991

The emission pattern of vocalizations and directionality of the sonar system in the echolocating bat, Pteronotus parnelli.

The radiation patterns of the first three harmonics (approx. 30, 60, 90 kHz) of the mustached bat biosonar signal were measured from vocalizations elicited by cortical microstimulation. The primary foci of the acoustic beam patterns were in front of the mouth but somewhat below the horizontal plane. The prominent second and third harmonics showed sharp cutoffs between 20 degrees and 30 degrees lateral to the midline. Sidelobes were found, suggesting the influence of some vocal tract interference. When compared with previously measured estimates of the directionality of the auditory system, the vocal emission patterns are roughly complementary: Regions of maximum auditory sensitivity are found in areas of submaximal power for the sonar pulse beam pattern. The result is that, for the two most important harmonics, the "biosonar system" (i.e., vocal beam pattern plus receiver directionality) has a broader and more uniform directionality than either component alone. Therefore, within a limited region of space, echo amplitude will vary less as a function of angular displacement. This reduces the confounding influences of absolute sound pressure level on interaural intensity differences.

Animals↗
PubMed1994

Analysis of acoustic elements and syntax in communication sounds emitted by mustached bats.

Mustached bats, Pteronotus parnellii parnellii spend most of their lives in the dark and use their auditory system for acoustic communication as well as echolocation. The sound spectrograms of their communication sounds or "calls" revealed that this species produces a rich variety of calls. These calls consist of one or more of the 33 different types of discrete sounds or "syllables" that are emitted singly and/or in combination. These syllables can be further classified as 19 simple syllables, 14 composites, and three subsyllables. Simple syllables consist of characteristic geometric patterns of CF (constant frequency), FM (frequency modulation), and NB (noise burst) sounds that are defined quantitatively using statistical criteria. Composites consist of simple syllables or subsyllables conjoined without any silent interval. Most syllable types exhibit a large intrinsic variation in their physical structure compared to the stereotypic echolocation pulses. Syllable domains are defined on the basis of multiple parameters, although these can be collapsed onto three dimensions that capture 99% of the measured variation among different types of syllables. Temporal analysis of multisyllabic constructs reveals several syntactical rules for syllable transitions.

Acoustics↗
PubMed1994

The brain-stem auditory-evoked response in the big brown bat (Eptesicus fuscus) to clicks and frequency-modulated sweeps.

Three experiments were performed to evaluate the effects of stimulus level on the brain-stem auditory-evoked response (BAER) in the big brown bat (Eptesicus fuscus), a species that uses frequency-modulated (FM) sonar sounds for echolocation. In experiment 1, the effects of click level on the BAER were investigated. Clicks were presented at levels of 30 to 90 dB pSPL in 10-dB steps. Each animal responded reliably to clicks at levels of 50 dB pSPL and above, showing a BAER containing four peaks in the first 3-4 ms from click onset (waves i-iv). With increasing click level, BAER peak amplitude increased and peak latency decreased. A decrease in the i-iv interval also occurred with increasing click level. In experiment 2, stimuli were 1-ms linear FM sweeps, decreasing in frequency from 100 to 20 kHz. Stimulus levels ranged from 20 to 90 dB pSPL. BAERs to FM sweeps were observed in all animals for levels of 40 dB pSPL and above. These responses were similar to the click-evoked BAER in waveform morphology, with the notable exception of an additional peak observed at the higher levels of FM sweeps. This peak (wave ia) occurred prior to the first wave seen at lower levels (wave ib). As the level of the FM sweep increased, there was a decrease in peak latency and an increase in peak amplitude. Similarity in the magnitude and behavior of the i-iv and ib-iv intervals suggests that wave ib to FM sweeps is the homolog of the wave i response to click stimuli. Experiment 3 tested the hypothesis that wave ia represented activity emanating from more basal cochlear regions than wave ib. FM sweeps (100-20 kHz) were presented at 90 dB pSPL, and broadband noise was raised in level until the BAER was eliminated. This "masked threshold" occurred at 85 dB SPL of noise. At masked threshold, the broadband noise was steeply high-pass filtered at five cutoff frequencies ranging from 20 to 80 kHz. Generally, wave ia was eliminated for masker cutoff frequencies of 56.6 kHz and below, while wave ib was typically observed for masker cutoffs down to 28.3 kHz. The results of these three experiments are compared and contrasted with data from other mammalian BAER studies.

Acoustic Stimulation↗
PubMed2000

Foliage echoes: a probe into the ecological acoustics of bat echolocation.

The research reported here aims at understanding the biosonar system of bats based on the properties of its natural inputs (ecological acoustics). Echoes from foliages are studied as examples of ubiquitous, natural targets. The echo properties and their qualitative relationship to plant architecture are described. The echoes were found to be profoundly stochastic and in general neither Gaussian nor stationary. Consequently, features useful for discrimination of such target classes will be confined to estimated random process parameters. Several such statistical signal features which are sufficiently invariant to allow a classification of the used example plants were identified: the characteristic exponent and the dispersion of an alpha-stable model for the amplitude distribution, a crest factor defined as the ratio of maximum squared amplitude and signal energy, the dispersion of the first threshold passage distribution, the structure of the correlation matrix, and a nonstationarity in sound channel gain. Discrimination error probability could be reduced by combining features pairwise. The best combination was the crest factor and the correlation coefficient of a log-linear model of the time-variant sound channel gain; it yielded an estimated Bayes risk of 6.9% for data pooled from different views.

Acoustics↗
PubMed2005

Bats are natural reservoirs of SARS-like coronaviruses.

Severe acute respiratory syndrome (SARS) emerged in 2002 to 2003 in southern China. The origin of its etiological agent, the SARS coronavirus (SARS-CoV), remains elusive. Here we report that species of bats are a natural host of coronaviruses closely related to those responsible for the SARS outbreak. These viruses, termed SARS-like coronaviruses (SL-CoVs), display greater genetic variation than SARS-CoV isolated from humans or from civets. The human and civet isolates of SARS-CoV nestle phylogenetically within the spectrum of SL-CoVs, indicating that the virus responsible for the SARS outbreak was a member of this coronavirus group.

Amino Acid Sequence↗
PubMed1965

Hearing sensitivity in bats.

Absolute hearing thresholds for two bats were determined by an operant conditioning technique. Pure tones rangingFrom 2.5 to 100 kilocycles per second were perceived by a single Eptesicus fuscus. Its maximum sensitivity was on the order of 68 decibles below 1 dyne per square centimeter and occurred at 20 kc/ sec. Maximum sensitivity for a single Myotis lucifugus was about 64 db below 1 dyne/ cm2 and occurred at 40 kc/ sec. The Myotis clearly heard a tone of120 kc/ sec but gave no evidence of hearing below 10 kc/ sec.

Animals↗
PubMed1969

Interpubic ligament: elasticity in pregnant free-tailed bat.

The disparity between the size of the bony pelvis of a pregncant free-tailed bat and the single full-term fetus is so great that in order for birth to occur the interpublic ligament has to stretch to more than 15 times its original length. It is a living elastic band that contains an abundance of elastic fibers.

Animals↗