Natasha Mhatre, Fernando Montealegre-Z, Rohini Balakrishnan, Daniel Robert
(2009): Mechanical response of the tympanal membranes of the tree cricket
Oecanthus henryi. J. Comp. Physiol. A, 195 (5), 453-462.
Abstract: Crickets have two tympanal membranes on the tibiae of each foreleg.
Among several field cricket species of the genus Gryllus (Gryllinae), the
posterior tympanal membrane (PTM) is significantly larger than the anterior
membrane (ATM). Laser Doppler vibrometric measurements have shown that the
smaller ATM does not respond as much as the PTM to sound. Hence the PTM has
been suggested to be the principal tympanal acoustic input to the auditory
organ. In tree crickets (Oecanthinae), the ATM is slightly larger than the PTM.
Both membranes are structurally complex, presenting a series of transverse
folds on their surface, which are more pronounced on the ATM than on the PTM.
The mechanical response of both membranes to acoustic stimulation was
investigated using microscanning laser Doppler vibrometry. Only a small portion
of the membrane surface deflects in response to sound. Both membranes exhibit
similar frequency responses, and move out of phase with each other, producing
compressions and rarefactions of the tracheal volume backing the tympanum.
Therefore, unlike field crickets, tree crickets may have four instead of two
functional tympanal membranes. This is interesting in the context of the
outstanding question of the role of spiracular inputs in the auditory system of
tree crickets.
URL: http://www.springerlink.com/content/bu6mh151255w9115/
For reprints please contact Fernando Montealegre-Z (Email:
Susan SÃmer, Annette Denzinger, Hans-Ulrich Schnitzler (2009): Spatial
unmasking in the echolocating Big Brown Bat, Eptesicus fuscus. J. Comp.
Physiol. A, 195 (5), 463-472.
Abstract: Masking affects the ability of echolocating bats to detect a target
in the presence of clutter targets. It can be reduced by spatially separating
the targets. Spatial unmasking was measured in a two-alternative-forced-choice
detection experiment with four Big Brown Bats detecting a wire at 1 m distance.
Depth dependent spatial unmasking was investigated by the bats detecting a wire
with a diameter of 1.2 mm in front of a masker with a threshold distance of 11
cm behind the wire. For angle dependent spatial unmasking the masker was turned
laterally, starting from its threshold position at 11 cm. With increasing
masker angles the bats could detect thinner wires with diameters decreasing
from 1.2 mm (target strength â36.8 dB) at 0Â to 0.2 mm (target strength â63.0
dB) at 22Â. Without masker, the bats detected wire diameters of 0.16 mm (target
strength â66.2 dB), reached with masker positions beyond 23Â (complete masking
release). Analysis of the sonar signals indicated strategies in the
echolocation behavior. The bats enhanced the second harmonics of their signals.
This may improve the spatial separation between wire and masker due to
frequency-dependent directionality increase of sound emission and echo
reception.
URL: http://www.springerlink.com/content/101t52874712q177/
For reprints please contact Hans-Ulrich Schnitzler (Corresponding author;
Email:
Anthony E. Petrites, Oliver S. Eng, Donald S. Mowlds, James A. Simmons,
Caroline M. DeLong (2009): Interpulse interval modulation by echolocating big
brown bats (Eptesicus fuscus) in different densities of obstacle clutter. J.
Comp. Physiol. A, 195 (6), 603-617.
Abstract: Big brown bats (Eptesicus fuscus) use biosonar to find insect prey in
open areas, but they also find prey near vegetation and even fly through
vegetation when in transit from roosts to feeding sites. To evaluate their
reactions to dense, distributed clutter, bats were tested in an obstacle array
consisting of rows of vertically hanging chains. Chains were removed from the
array to create a curved corridor of three clutter densities (high, medium,
low). Bats flew along this path to receive a food reward after landing on the
far wall. Interpulse intervals (IPIs) varied across clutter densities to
reflect different compromises between using short IPIs for gathering echoes
rapidly enough to maneuver past the nearest chains and using longer IPIs so
that all echoes from one sound can be received before the next sound is
emitted. In high-clutter density, IPIs were uniformly shorter (20â65 ms) than
in medium and low densities (40â100 ms) and arranged in âstrobe groups,â with
some overlap of echo streams from different broadcasts, causing pulse-echo
ambiguity. As previously proposed, alternating short and long IPIs in strobe
groups may allow bats to focus on large-scale pathfinding tasks as well as
close-in obstacle avoidance.
URL: http://www.springerlink.com/content/eq06135750lx3241/
For reprints please contact Anthony E. Petrites (Email:
Simone JanÃen, Sabine Schmidt (2009): Evidence for a perception of prosodic
cues in bat communication: contact call classification by Megaderma lyra. J.
Comp. Physiol. A, 195 (7), 663-672.
Abstract: The perception of prosodic cues in human speech may be rooted in
mechanisms common to mammals. The present study explores to what extent bats
use rhythm and frequency, typically carrying prosodic information in human
speech, for the classification of communication call series. Using a
two-alternative, forced choice procedure, we trained Megaderma lyra to
discriminate between synthetic contact call series differing in frequency,
rhythm on level of calls and rhythm on level of call series, and measured the
classification performance for stimuli differing in only one, or two, of the
above parameters. A comparison with predictions from models based on one,
combinations of two, or all, parameters revealed that the bats based their
decision predominantly on frequency and in addition on rhythm on the level of
call series, whereas rhythm on level of calls was not taken into account in
this paradigm. Moreover, frequency and rhythm on the level of call series were
evaluated independently. Our results show that parameters corresponding to
prosodic cues in human languages are perceived and evaluated by bats. Thus,
these necessary prerequisites for a communication via prosodic structures in
mammals have evolved far before human speech.
URL: http://www.springerlink.com/content/t22r67528p11l111/
For reprints please contact Sabine Schmidt (Email:
Hannah M. ter Hofstede, Joanne Killow, James H. Fullard (2009): Gleaning bat
echolocation calls do not elicit antipredator behaviour in the Pacific field
cricket, Teleogryllus oceanicus (Orthoptera: Gryllidae). J. Comp. Physiol. A,
195 (8), 769-776.
Abstract: Bats that glean prey (capture them from surfaces) produce relatively
inconspicuous echolocation calls compared to aerially foraging bats and could
therefore be difficult predators to detect, even for insects with ultrasound
sensitive ears. In the cricket Teleogryllus oceanicus, an auditory interneuron
(AN2) responsive to ultrasound is known to elicit turning behaviour, but only
when the cricket is in flight. Turning would not save a cricket from a gleaning
bat so we tested the hypothesis that AN2 elicits more appropriate antipredator
behaviours when crickets are on the ground. The echolocation calls of
Nyctophilus geoffroyi, a sympatric gleaning bat, were broadcast to singing male
and walking female T. oceanicus. Males did not cease singing and females did
not pause walking more than usual in response to the bat calls up to
intensities of 82 dB peSPL. Extracellular recordings from the cervical
connective revealed that the echolocation calls elicited AN2 action potentials
at high firing rates, indicating that the crickets could hear these stimuli.
AN2 appears to elicit antipredator behaviour only in flight, and we discuss
possible reasons for this context-dependent function.
URL: http://www.springerlink.com/content/axr07402t3w2g203/
For reprints please contact Hannah M. ter Hofstede (Email:
Jedediah Tressler & Michael S. Smotherman (2009): Context-dependent effects of
noise on echolocation pulse characteristics in free-tailed bats. J. Comp.
Physiol. A, 195 (10), 923-934.
Abstract: Background noise evokes a similar suite of adaptations in the
acoustic structure of communication calls across a diverse range of
vertebrates. Echolocating bats may have evolved specialized vocal strategies
for echolocating in noise, but also seem to exhibit generic vertebrate
responses such as the ubiquitous Lombard response. We wondered how bats balance
generic and echolocation-specific vocal responses to noise. To address this
question, we first characterized the vocal responses of flying free-tailed bats
(Tadarida brasiliensis) to broadband noises varying in amplitude. Secondly, we
measured the batsâ responses to band-limited noises that varied in the extent
of overlap with their echolocation pulse bandwidth. We hypothesized that the
batsâ generic responses to noise would be graded proportionally with noise
amplitude, total bandwidth and frequency content, and consequently that more
selective responses to band-limited noise such as the jamming avoidance
response could be explained by a linear decomposition of the response to
broadband noise. Instead, the results showed that both the nature and the
magnitude of the vocal responses varied with the acoustic structure of the
outgoing pulse as well as non-linearly with noise parameters. We conclude that
free-tailed bats utilize separate generic and specialized vocal responses to
noise in a context-dependent fashion.
URL: http://www.springerlink.com/content/4726421780767u44/
For reprints please contact Jedediah Tressler (Email:
Navdeep S. Asi, James Howard Fullard, Scott Whitehead & Jeff W. Dawson (2009):
No neural evidence for dynamic auditory tuning of the A1 receptor in the ear of
the noctuid moth, Noctua pronuba. J. Comp. Physiol. A, 195 (10), 955-960.
Abstract: By examining the mechanical properties of the tympanum of the noctuid
moth, Noctua pronuba, Windmill et al. (2006) suggested that this insect
increases (up-tunes) the frequencies of its best hearing when exposed to high
intensity sounds (HIS) resembling the echolocation calls of attacking bats. We
tested whether this biophysical phenomenon was encoded in the neural responses
of this mothâs most sensitive auditory receptor (A1 cell) before and after
exposure to HIS. We measured: (1) the number of A1 action potentials (spikes)
per stimulus pulse; (2) the proportion of A1 spike periods below that
determined to elicit evasive flight maneuvers and, (3) the change in A1 cell
firing (spike number, interspike interval, stimulus/spike latency) over a
duration of time similar to that in which up-tuning lasts. We observed no
significant spiking response changes in the predicted direction to any of the
frequencies tested following exposure to HIS and we observed only two of the 24
predicted time-dependent changes to A1 firing. These results indicate that
tympanal up-tuning does not result in a change to this mothâs auditory
frequency sensitivity and we suggest either sensillar resonances or increases
in thoracic muscle tension following exposure to HIS as alternative
explanations.
URL: http://www.springerlink.com/content/v87282133h435172/
For reprints please contact James Howard Fullard (Email:
Kelly E. Radziwon, Kristie M. June, Daniel J. Stolzberg, Matthew A.
Xu-Friedman, Richard J. Salvi & Micheal L. Dent (2009): Behaviorally measured
audiograms and gap detection thresholds in CBA/CaJ mice. J. Comp. Physiol. A,
195 (10), 961-969.
Abstract: Tone detection and temporal gap detection thresholds were determined
in CBA/CaJ mice using a Go/No-go procedure and the psychophysical method of
constant stimuli. In the first experiment, audiograms were constructed for five
CBA/CaJ mice. Thresholds were obtained for eight pure tones ranging in
frequency from 1 to 42 kHz. Audiograms showed peak sensitivity between 8 and 24
kHz, with higher thresholds at lower and higher frequencies. In the second
experiment, thresholds for gap detection in broadband and narrowband noise
bursts were measured at several sensation levels. For broadband noise, gap
thresholds were between 1 and 2 ms, except at very low sensation levels, where
thresholds increased significantly. Gap thresholds also increased significantly
for low pass-filtered noise bursts with a cutoff frequency below 18 kHz. Our
experiments revised absolute auditory thresholds in the CBA/CaJ mouse strain
and demonstrated excellent gap detection ability in the mouse. These results
add to the baseline behavioral data from normal-hearing mice which have become
increasingly important for assessing auditory abilities in genetically altered
mice.
URL: http://www.springerlink.com/content/7t801332k486x7ku/
For reprints please contact Micheal L. Dent (Email:
R. Matthias Hennig (2009): Walking in Fourierâs space: algorithms for the
computation of periodicities in song patterns by the cricket Gryllus
bimaculatus. J. Comp. Physiol. A, 195 (10), 971-987.
Abstract: Is discrimination of the envelope of an acoustic signal based on
spectral or temporal computations? To investigate this question for the cricket
Gryllus bimaculatus, pattern envelopes were constructed by the addition of
several sine waves and modified by systematic phase changes. The phonotactic
response of female crickets towards such sinusoidal but also rectangular pulse
patterns was quantified on a locomotion compensator. Envelope patterns that
exhibited a modulation frequency of 25 Hz as the dominant frequency were
attractive and although changes of phase modified the temporal pattern, the
values of attractiveness remained unaffected. Removal of the 25-Hz component
reduced the phonotactic scores. Patterns in which other frequency components
exhibited a larger amplitude than the 25-Hz component were less attractive.
However, the combination of an unattractive pulse period with the attractive
modulation frequency of 25 Hz in a pattern revealed that such stimuli were
unattractive despite the presence of the 25-Hz component. A comparison of the
attractiveness of all patterns revealed that female crickets evaluated the
duration of pulse period over a wide range of duty cycles. The combined
evidence showed that pattern envelopes were processed in the time- and not in
the spectral domain.
URL: http://www.springerlink.com/content/p2246783323w1504/
For reprints please contact R. Matthias Hennig (Email:
Karen P. Maruska & Timothy C. Tricas (2009): Encoding properties of auditory
neurons in the brain of a soniferous damselfish: response to simple tones and
complex conspecific signals. J. Comp. Physiol. A, 195 (11), 1071-1088.
Abstract: The fish auditory system encodes important acoustic stimuli used in
social communication, but few studies have examined response properties of
central auditory neurons to natural signals. We determined the features and
responses of single hindbrain and midbrain auditory neurons to tone bursts and
playbacks of conspecific sounds in the soniferous damselfish, Abudefduf
abdominalis. Most auditory neurons were either silent or had slow irregular
resting discharge rates <20 spikes sâ1. Average best frequency for neurons to
tone stimuli was ~130 Hz but ranged from 80 to 400 Hz with strong
phase-locking. This low-frequency sensitivity matches the frequency band of
natural sounds. Auditory neurons were also modulated by playbacks of
conspecific sounds with thresholds similar to 100 Hz tones, but these
thresholds were lower than that of tones at other test frequencies. Thresholds
of neurons to natural sounds were lower in the midbrain than the hindbrain.
This is the first study to compare response properties of auditory neurons to
both simple tones and complex stimuli in the brain of a recently derived
soniferous perciform that lacks accessory auditory structures. These data
demonstrate that the auditory fish brain is most sensitive to the frequency and
temporal components of natural pulsed sounds that provide important signals for
conspecific communication.
URL: http://www.springerlink.com/content/k28334u02639vv8v/
For reprints please contact Karen P. Maruska (Email:
Kind regards
Sonja Amoser
**************************
Dr. Sonja Amoser
SteinrieglstraÃe 286
3400 Weidlingbach
Austria
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