共查询到20条相似文献,搜索用时 46 毫秒
1.
Martin Singheiser Dennis T. T. Plachta Sandra Brill Peter Bremen Robert F. van der Willigen Hermann Wagner 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2010,196(3):227-240
We studied the influence of frequency on sound localization in free-flying barn owls by quantifying aspects of their target-approaching
behavior to a distant sound source during ongoing auditory stimulation. In the baseline condition with a stimulus covering
most of the owls hearing range (1–10 kHz), all owls landed within a radius of 20 cm from the loudspeaker in more than 80%
of the cases and localization along the azimuth was more accurate than localization in elevation. When the stimulus contained
only high frequencies (>5 kHz) no changes in striking behavior were observed. But when only frequencies from 1 to 5 kHz were
presented, localization accuracy and precision decreased. In a second step we tested whether a further border exists at 2.5 kHz
as suggested by optimality models. When we compared striking behavior for a stimulus having energy from 2.5 to 5 kHz with
a stimulus having energy between 1 and 2.5 kHz, no consistent differences in striking behavior were observed. It was further
found that pre-takeoff latency was longer for the latter stimulus than for baseline and that center frequency was a better
predictor for landing precision than stimulus bandwidth. These data fit well with what is known from head-turning studies
and from neurophysiology. 相似文献
2.
P. J. Fonseca A. V. Popov 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(4):417-427
1. Laser vibrometry and acoustic measurements were used to study the biophysics of directional hearing in males and females
of a cicada, in which most of the male tympanum is covered by thick, water filled tissue “pads”. 2. In females, the tympanal
vibrations are very dependent on the direction of sound incidence in the entire frequency range 1–20 kHz, and especially at
the main frequencies of the calling song (3–7 kHz). At frequencies up to 10 kHz, the directionality disappears if the contralateral
tympanum, metathoracic spiracle, and folded membrane are blocked with Vaseline. This suggests some pressure-difference receiver
properties in the ear. 3. In males, the tympanal vibrations depend on the direction of sound incidence only within narrow
frequency bands (around 1.8 kHz and at 6–7 kHz). At frequencies above 10–12 kHz, the directionality appears to be determined
by diffraction, and the ear seems to work as a pressure receiver. The peak in directionality at 6–7 kHz disappears when the
contralateral timbal, but not the tympanum, is covered. Covering the thin ventral abdominal wall causes the peak around 1.8 kHz
to disappear. 4. Most observed tympanal directionalities, except around 1.8 kHz in males, are well predicted from measured
transmissions of sound through the body and measured values of sound amplitude and phase at the ears at various directions
of sound incidence.
Accepted: 18 October 1996 相似文献
3.
Absolute hearing thresholds and critical masking ratios in the European barn owl: a comparison with other owls 总被引:1,自引:0,他引:1
M. L. Dyson G. M. Klump B. Gauger 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1998,182(5):695-702
Absolute thresholds and critical masking ratios were determined behaviorally for the European barn owl (Tyto alba guttata). It shows an excellent sensitivity throughout its hearing range with a minimum threshold of −14.2 dB sound pressure level
at 6.3 kHz, which is similar to the sensitivity found in the American barn owl (Tyto alba pratincola) and some other owls. Both the European and the American barn owl have a high upper-frequency limit of hearing exceeding
that in other bird species. Critical masking ratios, that can provide an estimate for the frequency selectivity in the barn
owl's hearing system, were determined with a noise of about 0 dB spectrum level. They increased from 19.1 dB at 2 kHz to 29.2 dB
at 8 kHz at a rate of 5.1 dB per octave. The corresponding critical ratio bandwidths were 81, 218, 562 and 831 Hz for test-tone
frequencies of 2, 4, 6.3 and 8 kHz, respectively. These values indicate, contrary to expectations based on the spatial representation
of frequencies on the basilar papilla, increasing bandwidths of auditory filters in the region of the barn owl's auditory
fovea. This increase, however, correlates with the increase in the bandwidths of tuning curves in the barn owl's auditory
fovea.
Accepted: 27 November 1997 相似文献
4.
Jayne E. Yack Elisabeth K. V. Kalko Annemarie Surlykke 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2007,193(6):577-590
Nocturnal Hedyloidea butterflies possess ultrasound-sensitive ears that mediate evasive flight maneuvers. Tympanal ear morphology,
auditory physiology and behavioural responses to ultrasound are described for Macrosoma heliconiaria, and evidence for hearing is described for eight other hedylid species. The ear is formed by modifications of the cubital
and subcostal veins at the forewing base, where the thin (1–3 μm), ovoid (520 × 220 μm) tympanal membrane occurs in a cavity.
The ear is innervated by nerve IIN1c, with three chordotonal organs attaching to separate regions of the tympanal membrane.
Extracellular recordings from IIN1c reveal sensory responses to ultrasonic (>20 kHz), but not low frequency (<10 kHz) sounds.
Hearing is broadly tuned to frequencies between 40 and 80 kHz, with best thresholds around 60 dB SPL. Free flying butterflies
exposed to ultrasound exhibit a variety of evasive maneuvers, characterized by sudden and unpredictable changes in direction,
increased velocity, and durations of ∼500 ms. Hedylid hearing is compared to that of several other insects that have independently
evolved ears for the same purpose-bat detection. Hedylid hearing may also represent an interesting example of evolutionary
divergence, since we demonstrate that the ears are homologous to low frequency ears in some diurnal Nymphalidae butterflies. 相似文献
5.
F. Ladich H. Y. Yan 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1998,182(6):737-746
Several anabantoid species produce broad-band sounds with high-pitched dominant frequencies (0.8–2.5 kHz), which contrast
with generally low-frequency hearing abilities in (perciform) fishes. Utilizing a recently developed auditory brainstem response
recording-technique, auditory sensitivities of the gouramis Trichopsis vittata, T. pumila, Colisa lalia, Macropodus opercularis and Trichogaster trichopterus were investigated and compared with the sound characteristics of the respective species. All five species exhibited enhanced
sound-detecting abilities and perceived tone bursts up to 5 kHz, which qualifies this group as hearing specialists. All fishes
possessed a high-frequency sensitivity maximum between 800 Hz and 1500 Hz. Lowest hearing thresholds were found in T. trichopterus (76 dB re 1 μPa at 800 Hz). Dominant frequencies of sounds correspond with the best hearing bandwidth in T. vittata (1–2 kHz) and C. lalia (0.8–1 kHz). In the smallest species, T. pumila, dominant frequencies of acoustic signals (1.5–2.5 kHz) do not match lowest thresholds, which were below 1.5 kHz. However,
of all species studied, T. pumila had best hearing sensitivity at frequencies above 2 kHz. The association between high-pitched sounds and hearing may be caused
by the suprabranchial air-breathing chamber, which, lying close to the hearing and sonic organs, enhances both sound perception
and emission at its resonant frequency.
Accepted: 26 November 1997 相似文献
6.
Doreen Möckel Ernst-August Seyfarth Manfred Kössl 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2007,193(8):871-879
Tympanal organs of insects emit distortion-product otoacoustic emissions (DPOAEs) that are indicative of nonlinear ear mechanics.
Our study sought (1) to define constraints of DPOAE generation in the ear of Locusta migratoria, and (2) to identify the sensory structures involved. We selectively destroyed the connection between the (peripheral) sensory
ganglion and the tympanal attachment points of the “d-cell” dendrites; d-cells are most sensitive to sound frequencies above
12 kHz. This led to a decrease of DPOAEs that were evoked by f
2 frequencies above 15 kHz (decrease of 15–40 dB; mean 28 dB; n = 12 organs). DPOAEs elicited by lower frequencies remained unchanged. Such frequency-specific changes following the exclusion
of one scolopidial sub-population suggest that these auditory scolopidia are in fact the source of DPOAEs in insects. Electrical
stimulation of the auditory nerve (with short current pulses of 4–10 μA or DC-currents of 0.5 μA) reversibly reduced DPOAEs
by as much as 30 dB. We assume that retrograde electrical stimulation primarily affected the neuronal part of the scolopidia.
Severing the auditory nerve from the central nervous system (CNS) did not alter the DPOAE amplitudes nor the effects of electrical
stimulation. 相似文献
7.
The directionally sensitive acoustics of the pinnae enable humans to perceive the up–down and front–back direction of sound.
This mechanism complements another, independent mechanism that derives sound-source azimuth from interaural difference cues.
The pinnae effectively add direction-dependent spectral notches and peaks to the incoming sound, and it has been shown that
such features are used to code sound direction in the median plane. However, it is still unclear which of the pinna-induced
features play a role in sound localization. The present study presents a method for the reconstruction of the spatially relevant
features in the spectral domain. Broadband sounds with random spectral shapes were presented in rapid succession as subjects
made saccadic eye movements toward the perceived stimulus locations. The analysis, which is based on Bayesian statistics,
indicates that specific spectral features could be associated with perceived spatial locations. Spectral features that were
determined by this psychophysical method resemble the main characteristics of the pinna transfer functions obtained from acoustic
measurements in the ear canal. Despite current experimental limitations, the approach may prove useful in the study of perceptually
relevant spectral cues underlying human sound localization.
Received: 2 December 2000 / Accepted in revised form: 23 October 2001 相似文献
8.
Isam A. Mohamed Ahmed Jiro Arima Tsuyoshi Ichiyanagi Emi Sakuno Nobuhiro Mori 《World journal of microbiology & biotechnology》2010,26(8):1455-1464
Soil isolates, identified as Pseudomonas sp. strain A9 and Pseudomonas sp. strain B9b (based on the phenotypic features and phylogenetic analysis) were found to degrade homocholine aerobically.
Morphological characterization using the optical microscope under light and phase contrast conditions showed that cells of
strain A9 formed short rods measuring approximately 0.5–1 × 1.5–2.0 μm in size while those of B9b formed long rods of 0.5–1 × 2.5–3.0 μm
during the early growth phase on both nutrient broth and basal-homocholine (basal-HC) media. Strain A9 was able to grow on
basal-HC medium at a wide range of temperatures (4–41°C) whereas strain B9b was not able to grow at either 4 or 41°C. Comparative
16S rRNA sequencing studies indicated that strain A9 fell into the Pseudomonas putida subclade whereas strain B9b located in Pseudomonas fulva subclade. Washed cells of strains A9 and B9b degraded homocholine completely within 6 h with concomitant formation of several
metabolites. Analysis of the metabolites by capillary electrophoresis, fast atom bombardment–mass spectrometry, and gas chromatography–mass
spectrometry, showed trimethylamine (TMA) as the major metabolite beside β-alanine betaine and trimethylaminopropionaldehyde.
Therefore, the possible degradation pathway of homocholine in the isolated strains is through successive oxidation of the
alcohol group (–OH) to aldehyde (–CHO) and acid (–COOH), and thereafter the cleavage of β-alanine betaine C–N bonds yielding
trimethylamine and an alkyl chain. 相似文献
9.
Background
It has been believed that location of the perforation has a significant impact on hearing loss. However, recent studies have demonstrated that the perforation sites had no impact on hearing loss. We measured the velocity and pattern of the manubrium vibration in guinea pigs with intact and perforated eardrum using a laser Doppler vibrometer in order to determine the effects of different location perforations on the middle ear transfer functions.Methods
Two bullas from 2 guinea pigs were used to determine stability of the umbo velocities, and 12 bullas from six guinea pigs to determine the effects of different location perforations on sound transmission. The manubrium velocity was measured at three points on the manubrium in the frequencies of 0.5–8 kHz before and after a perforation was made. The sites of perforations were in anterior-inferior (AI) quadrants of left ears and posterior-inferior (PI) quadrants of right ears.Results
The manubrium vibration velocity losses were noticed in the perforated ears only below 1.5 kHz. The maximum velocity loss was about 7 dB at 500 Hz with the PI perforation. No significant difference in the velocity loss was found between AI and PI perforations. The average ratio of short process velocity to the umbo velocity was approximately 0.5 at all frequencies. No significant differences were found before and after perforation at all frequencies (p>0.05) except 7 kHz (p = 0.004) for both AI and PI perforations.Conclusions
The manubrium vibration velocity losses from eardrum perforation were frequency-dependent and the largest losses occur at low frequencies. Manubrium velocity losses caused by small acute inferior perforations in guinea pigs have no significant impact on middle ear sound transmission at any frequency tested. The manubrium vibration axis may be perpendicular to the manubrium below 8 kHz in guinea pigs. 相似文献10.
Guohua Ma Jaime A. Teixeira da Silva Jinfeng Lü Xinhua Zhang Jietang Zhao 《Plant Cell, Tissue and Organ Culture》2011,105(3):355-361
An efficient propagation and regeneration system via direct shoot organogenesis for an endangered species, Metabriggsia ovalifolia, was established. High activity cytokinins [6-benzyladeneine (BA) and thidiazuron (TDZ)] and low activity auxins [α-naphthaleneacetic
acid (NAA), indole-3-butyric acid (IBA) and indole-3-acetic acid (IAA)] could directly induce adventitious shoots from leaf
or petiole explants within 5 weeks. Cytokinins (TDZ or BA) combined with auxin (NAA) in the induction media induced more adventitious
shoots than when auxins or cytokinins were used alone. Adventitious shoots could be induced and also mass-propagated on media
containing 2.5–5.0 μM TDZ (or BA) and 0.25–0.5 μM NAA. Adventitious roots differentiated at the proximal end of shoots on
rooting media containing half-strength MS salts and 0.5 μM IBA, 0.5 μM NAA, 0.1% activated charcoal or no plant growth regulators.
Over 90% of plantlets survived following acclimatization and transfer to a potting mixture (1:1, sand:vermiculite) in basins. 相似文献
11.
A. D. S. Bala T. T. Takahashi 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2000,186(5):425-434
The pupil of an awake, untrained, head-restrained barn owl was found to dilate in response to sounds with a latency of about
25 ms. The magnitude of the dilation scaled with signal-to-noise ratio. The dilation response habituated when a sound was
repeated, but recovered when stimulus frequency or location was changed. The magnitude of the recovered response was related
to the degree to which habituating and novel stimuli differed and was therefore exploited to measure frequency and spatial
discrimination. Frequency discrimination was examined by habituating the response to a reference tone at 3 kHz or 6 kHz and
determining the minimum change in frequency required to induce recovery. We observed frequency discrimination of 125 Hz at
3 kHz and 250 Hz at 6 kHz – values comparable to those reported by others using an operant task. Spatial discrimination was
assessed by habituating the response to a stimulus from one location and determining the minimum horizontal speaker separation
required for recovery. This yielded the first measure of the minimum audible angle in the barn owl: 3° for broadband noise
and 4.5° for narrowband noise. The acoustically evoked pupillary dilation is thus a promising indicator of auditory discrimination
requiring neither training nor aversive stimuli.
Accepted: 28 February 2000 相似文献
12.
G. G. S. Martius A. Wießner U. Stottmeister 《Applied microbiology and biotechnology》1996,45(5):692-699
Investigations into aerobic biological degrada-tion were carried out as part of an extensive programme designed to facilitate
the cheap remediation of a pyrolysis waste-water deposit. Attention was focused on the processes of carbon conversion by different
populations. The susceptibility of a body of lignite-processing deposit water to microbiological degradation was examined
in batch investigations in a Sapromat system and in continuous bench-scale fermenter cultivations, with respect to nutrient
supply, inoculation culture and molecular size distribution. It was found that degradation best occurs with an adapted mixed
culture. The autochthonous culture removes 30% less dissolved organic carbon (DOC) and has a 40% higher specific oxygen demand.
A shortage of phosphorus, investigated with a view to avoiding additional eutrophication problems in the open water in the
case of in situ remediation, causes reduced DOC degrada-tion and significantly higher specific oxygen demand. The biological
process is overlapped by abiotic oxidation. During aerobic treatment, a concentration of colour-giving aromatic substances
of between 0.5 kDa and 5 kDa was observed. This phenomenon is caused by the oxidation of low- and high-molecular-mass compounds.
The removal of DOC is limited to 65% and mainly occurs in the range below 0.5 kDa (30%) and in the 0.5–1 kDa range (12%);
the removal is negligible in the ranges 1–3 kDa (0.8%) and 3–5 kDa (2%) and a little higher in the ranges 5 kDa–0.3 μm (5%)
and above 0.3 μm (6%). In the investigations it was discovered that DOC removal causes in the ranges below 0.5 kDa, 0.5–1
kDa and 5 kDa–0.3 μm mainly as a result of degradation, but the range above 0.3 μm is chiefly caused by bioadsorption. Aerobic
microbiological treatment is able to remove most low-molecular-mass substances. In order to remove the macromolecular and
colour-giving part of the deposit water, an additional treatment stage, e.g. flocculation, is required.
Received: 10 October 1995/Received revision: 9 January 1996/Accepted: 15 January 1996 相似文献
13.
Julio C. Hechavarría Ariadna T. Cobo Yohami Fernández Silvio Macías Manfred Kössl Emanuel C. Mora 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2011,197(12):1159-1172
Frequency tuning, temporal response pattern and latency properties of inferior colliculus neurons were investigated in the
big fruit-eating bat, Artibeus jamaicensis. Neurons having best frequencies between 48–72 kHz and between 24–32 kHz are overrepresented. The inferior colliculus neurons
had either phasic (consisting in only one response cycle at all stimulus intensities) or long-lasting oscillatory responses
(consisting of multiple response cycles). Seventeen percent of neurons displayed paradoxical latency shift, i.e. their response
latency increased with increasing sound level. Three types of paradoxical latency shift were found: (1) stable, that does
not depend on sound duration, (2) duration-dependent, that grows with increasing sound duration, and (3) progressive, whose
magnitude increases with increasing sound level. The temporal properties of paradoxical latency shift neurons compare well
with those of neurons having long-lasting oscillatory responses, i.e. median inter-spike intervals and paradoxical latency
shift below 6 ms are overrepresented. In addition, oscillatory and paradoxical latency shift neurons behave similarly when
tested with tones of different durations. Temporal properties of oscillation and PLS found in the IC of fruit-eating bats
are similar to those found in the IC of insectivorous bats using downward frequency-modulated echolocation calls. 相似文献
14.
Background
Barn owls integrate spatial information across frequency channels to localize sounds in space.Methodology/Principal Findings
We presented barn owls with synchronous sounds that contained different bands of frequencies (3–5 kHz and 7–9 kHz) from different locations in space. When the owls were confronted with the conflicting localization cues from two synchronous sounds of equal level, their orienting responses were dominated by one of the sounds: they oriented toward the location of the low frequency sound when the sources were separated in azimuth; in contrast, they oriented toward the location of the high frequency sound when the sources were separated in elevation. We identified neural correlates of this behavioral effect in the optic tectum (OT, superior colliculus in mammals), which contains a map of auditory space and is involved in generating orienting movements to sounds. We found that low frequency cues dominate the representation of sound azimuth in the OT space map, whereas high frequency cues dominate the representation of sound elevation.Conclusions/Significance
We argue that the dominance hierarchy of localization cues reflects several factors: 1) the relative amplitude of the sound providing the cue, 2) the resolution with which the auditory system measures the value of a cue, and 3) the spatial ambiguity in interpreting the cue. These same factors may contribute to the relative weighting of sound localization cues in other species, including humans. 相似文献15.
Multiple shoot induction and callus regeneration in Sarcostemma brevistigma Wight & Arnott, a rare medicinal plant 总被引:1,自引:0,他引:1
An efficient micropropagation protocol based on multiple shoot induction and callus regeneration has been standardized in
Sarcostemma brevistigma, a rare medicinal plant. The nodal cuttings were cultured on MS medium supplemented with BA (0.5–8 μM) or Kn (0.5–8 μM) alone
or in combination with NAA (0.5–1.5 μM). Maximum multiple shoot induction was observed on MS medium supplemented with 4 μM
BA. On this medium, 100% cultures responded with an average number of 11.3 shoots per explant. However, the average shoot
length was limited to only 0.9 cm on this medium. The addition of 1 μM NAA along with 4 μM BA gave rise to an average number
of 10.9 shoots with an average shoot length of 1.8 cm. Luxuriantly growing callus was obtained on MS medium supplemented with
BA (5 μM) and 2,4-D (2 μM). The callus was subcultured on MS medium supplemented with BA (2–15 μM) or Kn (2–15 μM) alone or
in combination with NAA (0.5–2 μM) for shoot organogenesis. Optimum callus regeneration was obtained on MS medium supplemented
with 10 μM BA and 1 μM NAA. On this medium, 100% cultures responded with an average number of 13.4 shoots per culture. The
shoots obtained via multiple shoot induction and organogenesis were rooted on half-strength MS medium supplemented with NAA
(1–7 μM) or IBA (1–7 μM). IBA was better than NAA in terms of both the percentage of cultures that responded and the average
number of roots per explant. The rooted shoots were successfully transplanted to soil with 86% success. This standardized
protocol will help to conserve this rare medicinal plant. 相似文献
16.
Sarah A. Stamper Mary E. Bates Douglas Benedicto James A. Simmons 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2009,195(1):79-89
Big brown bats (Eptesicus fuscus) emit frequency-modulated (FM) echolocation sounds containing two principal down-sweeping harmonics (FM1 ~ 55–25 kHz, FM2 ~ 105–50 kHz). To determine whether each harmonic contributes to perception of echo delay, bats were trained to discriminate
between “split-harmonic” echoes that differed in delay. The bat’s broadcasts were picked up with microphones, and FM1 and FM2 were separated with highpass and lowpass filters at about 55 kHz, where they overlap in frequency. Both harmonics then were
delivered from loudspeakers as positive stimuli in a 2-choice delay discrimination procedure with FM1 delayed 3.16 ms and FM2 delayed 3.46 ms (300 μs delay split). Negative stimuli contained FM1 and FM2 with the same filtering but no delay separation. These were presented at different overall delays from 11 down to 3 ms to
measure the bat’s delay discrimination acuity for each harmonic in the split harmonic echoes. The bats determined the delays
of both FM1 and FM2, but performance was overlaid by a broad pedestal of poor performance that extended for 800 μs. Splitting the harmonics by
300 μs appears to defocus the bat’s representation of delay, revealing the existence of a process for recognizing the normally
simultaneous occurrence of the harmonics. 相似文献
17.
The characteristics of absolute auditory sensitivity of the bottlenose dolphin (Tursiops truncatus) in the transverse plane have been measured using short broadband stimuli simulating dolphin clicks (with energy maximum
at frequencies 8, 16, 30, 50 and 100 kHz). Experiments were performed using the method of conditioned reflexes with food reinforcement.
It is shown that, in the frequency range of 8–30 kHz, the absolute sensitivity of dolphin hearing in any ventral and lateral
directions of the transverse plane is only 2–8 dB worse than in the rostral direction. Moreover, it is 25–30 dB better than
at 50–100 kHz. At 8–30 kHz, pronounced dorsoventral asymmetry has been observed. In this frequency range, it reaches 15–18
dB whereas at 50–100 kHz this asymmetry decreases to 2–3 dB. In the dorsal direction, the auditory sensitivity is 18 dB worse
than in the rostral one at ∼8 kHz, and the difference rises smoothly to 33 dB at ∼100 kHz. At 50–100 kHz, the acoustical thresholds
in the transverse plane relative to those for the with rostral direction get worse almost uniformly in all directions by 25–33
dB. As a result, in the transverse plane the beam patterns are nearly circular, unlike those at 8–30 kHz. The results are
discussed in terms of the model of sound perception through the left and right mental foramens. The biological relevance of
such asymmetry is emphasized. 相似文献
18.
S. Credner H. Burda F. Ludescher 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(3):245-255
In captive adult Zambian mole-rats 14 different sounds (13 true vocalizations) have been recorded during different behavioural
contexts. The sound analysis revealed that all sounds occurred in a low and middle frequency range with main energy below
10 kHz. The majority of calls contained components of 1.6–2 kHz, 0.63–0.8 kHz, and/or 5–6.3 kHz. The vocalization range thus
matched well the hearing range as established in other studies. The frequency content of courtship calls in two species of
Zambian Cryptomys was compared with that in naked mole-rats (Heterocephalus glaber) and blind mole-rats (Spalax ehrenbergi) as described in the literature. The frequency range of maximum sound energy is negatively correlated with the body weight
and coincides with the frequencies of best hearing in the respective species. In general, the vocalization range in subterranean
mammals is shifted towards low frequencies which are best propagated in underground burrows.
Accepted: 16 September 1996 相似文献
19.
M. J. Ferragamo T. Haresign J. A. Simmons 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,182(1):65-79
Neurons in the inferior colliculus (IC) of the awake big brown bat, Eptesicus fuscus, were examined for joint frequency and latency response properties which could register the timing of the bat's frequency-modulated (FM) biosonar echoes. Best frequencies (BFs) range from 10 kHz to 100 kHz with 50% tuning widths mostly
from 1 kHz to 8 kHz. Neurons respond with one discharge per 2-ms tone burst or FM stimulus at a characteristic latency in
the range of 3–45 ms, with latency variability (SD) of 50 μs to 4–6 ms or more. BF distribution is related to biosonar signal
structure. As observed previously, on a linear frequency scale BFs appear biased to lower frequencies, with 20–40 kHz overrepresented.
However, on a hyperbolic frequency (linear period) scale BFs appear more uniformly distributed, with little overrepresentation.
The cumulative proportion of BFs in FM1 and FM2 bands reconstructs a scaled version of the spectrogram of FM broadcasts. Correcting FM latencies for absolute BF latencies
and BF time-in-sweep reveals a subset of IC cells which respond dynamically to the timing of their BFs in FM sweeps. Behaviorally,
Eptesicus perceives echo delay and phase with microsecond or even submicrosecond accuracy and resolution, but even with use of phase-locked
FM and tone-burst stimuli the cell-by-cell precision of IC time-frequency registration seems inadequate by itself to account
for the temporal acuity exhibited by the bat.
Accepted: 21 June 1997 相似文献
20.
The growth of black walnut shoot cultures was compared on media differing in nutrient formulation (MS, DKW, WPM, and 1/2X
DKW), cytokinin type (ZEA, BA, and TDZ), and cytokinin concentration. On WPM and 1/2X DKW media, hyperhydricity was observed
at frequencies of 60–100% compared with frequencies of 10–40% on the high-salt media (DKW and MS). All three cytokinins facilitated
shoot regeneration from nodal cuttings, but recurrent elongation was only observed for BA (5–12.5 μM) and ZEA (5–25 μM) with
mean shoot heights of 70–80 mm being possible after two culture periods (6–8 wk) for the fastest elongating lines. ZEA was
effective across all six shoot lines with mean shoot heights of at least 35 mm over two culture periods, but two of the shoot
lines were ‘nonresponsive’ to BA with mean shoot heights of <15 mm. In contrast, when shoot tip explants were used for culture
multiplication, ZEA was the least effective cytokinin with proliferation frequencies of only 30–40%. The proliferation frequencies
were twice as great (75–87%) for TDZ (0.05–0.1 μM), but most of the shoots regenerated were swollen or fasciated in morphology.
High rates of proliferation (61–88%) were also possible using BA (12.5–25 μM), but axillary shoots did not elongate well,
growing to heights of only 5–10 mm, on average, after 4–5 wk. Since the cytokinin types and concentrations required for high-frequency
(>50%) axillary proliferation had adverse effects on the morphology and growth potential of the shoots, multiplication strategies
based on the use of nodal cuttings are recommended. 相似文献