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New bioacoustic articles in J. Comp. Physiol. A Vol. 195

Subject: New bioacoustic articles in J. Comp. Physiol. A Vol. 195
From: "Sonja Amoser" <>
Date: Wed, 2 Jun 2010 22:19:20 +0200
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.

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 

For reprints please contact Hans-Ulrich Schnitzler (Corresponding author; 

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.

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.

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.

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.

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 

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 

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.

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.

For reprints please contact Karen P. Maruska (Email: 

Kind regards

Sonja Amoser

Dr. Sonja Amoser
SteinrieglstraÃe 286
3400 Weidlingbach

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