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Bioacoustic articles in J. Comp. Physiol. A Vol. 196 Issues 9 & 11

Subject: Bioacoustic articles in J. Comp. Physiol. A Vol. 196 Issues 9 & 11
From: "Sonja Amoser" <>
Date: Tue, 9 Nov 2010 10:20:59 +0100
Laura Hausmann, Mark von Campenhausen & Hermann Wagner (2010): Properties of 
low-frequency head-related transfer functions in the barn owl (Tyto alba). J. 
Comp. Physiol. A 196 (9), 601-612.

Abstract: The barn owl (Tyto alba) possesses several specializations regarding 
auditory processing. The most conspicuous features are the directionally 
sensitive facial ruff and the asymmetrically arranged ears. The 
frequency-specific influence of these features on sound has consequences for 
sound localization that might differ between low and high frequencies. Whereas 
the high-frequency range (>3 kHz) is well investigated, less is known about the 
characteristics of head-related transfer functions for frequencies below 3 kHz. 
In the present study, we compared 1/3 octaveband-filtered transfer functions of 
barn owls with center frequencies ranging from 0.5 to 9 kHz. The range of 
interaural time differences was 600 Îs at frequencies above 4 kHz, decreased to 
505 Îs at 3 kHz and increased again to about 615 Îs at lower frequencies. The 
ranges for very low (0.5â1 kHz) and high frequencies (5â9 kHz) were not 
statistically different. Interaural level differences and monaural gains 
increased monotonically with increasing frequency. No systematic influence of 
the body temperature on the measured localization cues was observed. These data 
have implications for the mechanism underlying sound localization and we 
suggest that the barn owlâs ears work as pressure receivers both in the high- 
and low-frequency ranges.

For reprints please contact L. Hausmann (email: 

Abhilash Ponnath & Hamilton E. Farris (2010): Calcium-dependent control of 
temporal processing in an auditory interneuron: a computational analysis. J. 
Comp. Physiol. A 196 (9), 613-628.

Abstract: Sensitivity to acoustic amplitude modulation in crickets differs 
between species and depends on carrier frequency (e.g., calling song vs. 
bat-ultrasound bands). Using computational tools, we explore how Ca2+-dependent 
mechanisms underlying selective attention can contribute to such differences in 
amplitude modulation sensitivity. For omega neuron 1 (ON1), selective attention 
is mediated by Ca2+-dependent feedback: [Ca2+]internal increases with 
excitation, activating a Ca2+-dependent after-hyperpolarizing current. We 
propose that Ca2+ removal rate and the size of the after-hyperpolarizing 
current can determine ON1âs temporal modulation transfer function (TMTF). This 
is tested using a conductance-based simulation calibrated to responses in vivo. 
The model shows that parameter values that simulate responses to single pulses 
are sufficient in simulating responses to modulated stimuli: no special 
modulation-sensitive mechanisms are necessary, as high and low-pass portions of 
the TMTF are due to Ca2+-dependent spike frequency adaptation and post-synaptic 
potential depression, respectively. Furthermore, variance in the two 
biophysical parameters is sufficient to produce TMTFs of varying bandwidth, 
shifting amplitude modulation sensitivity like that in different species and in 
response to different carrier frequencies. Thus, the hypothesis that the size 
of after-hyperpolarizing current and the rate of Ca2+ removal can affect 
amplitude modulation sensitivity is computationally validated.

For reprints please contact H. E. Farris (email: 

Konstantinos Kostarakos & Heiner RÃmer (2010): Sound transmission and 
directional hearing in field crickets: neurophysiological studies outdoors. J. 
Comp. Physiol. A 196 (9), 669-681.

Abstract: Many studies provide detailed behavioural and neurophysiological 
information on the ability of crickets to localize a sound source under ideal 
acoustic conditions, but very little is known about how they perform in real 
habitats. We investigated directional hearing of crickets in the field using a 
neurophysiological approach, by recording the activity of the two prominent, 
bilaterally homologous AN1 neurons simultaneously in a cricketâs habitat. The 
discharge and latency differences of the pair of neurons in response to 
conspecific chirps presented at different distances and directions were taken 
as a measure of directional information. The maximum hearing distance differed 
between individuals and weather conditions from 1 to 15 m (mean 9.2 m). 
Although the AN1 activity generally decreased with increasing distance, large 
fluctuations in the magnitude of responses occurred with distance, indicating 
that the intensity gradient over distance is often irregular. The directional 
information provided in the discharge differences of the two neurons also 
varied with distance. Again, there was no simple directional gradient on the 
transmission channel; rather, with decreasing distance to the source there were 
receiver locations providing suprathreshold responses, but no directional 
information. The consequences for the ability of field crickets to communicate 
acoustically close to the ground are discussed.

For reprints please contact K. Kostarakos (email: 

Gerlind U. C. Lehmann, Sandra Berger, Johannes StrauÃ, Arne W. Lehmann & 
Hans-Joachim PflÃger (2010): The auditory system of non-calling grasshoppers 
(Melanoplinae: Podismini) and the evolutionary regression of their tympanal 
ears. J. Comp. Physiol. A 196 (11), 807-816.

Abstract: Reduction of tympanal hearing organs is repeatedly found amongst 
insects and is associated with weakened selection for hearing. There is also an 
associated wing reduction, since flight is no longer required to evade bats. 
Wing reduction may also affect sound production. Here, the auditory system in 
four silent grasshopper species belonging to the Podismini is investigated. In 
this group, tympanal ears occur but sound signalling does not. The tympanal 
organs range from fully developed to remarkably reduced tympana. To evaluate 
the effects of tympanal regression on neuronal organisation and auditory 
sensitivity, the size of wings and tympana, sensory thresholds and sensory 
central projections are compared. Reduced tympanal size correlates with a 
higher auditory threshold. The threshold curves of all four species are tuned 
to low frequencies with a maximal sensitivity at 3â5 kHz. Central projections 
of the tympanal nerve show characteristics known from fully tympanate acridid 
species, so neural elements for tympanal hearing have been strongly conserved 
across these species. The results also confirm the correlation between 
reduction in auditory sensitivity and wing reduction. It is concluded that the 
auditory sensitivity of all four species may be maintained by stabilising 
selective forces, such as predation.

For reprints please contact G. U. C. Lehmann (email: 

Kind regards

Sonja Amoser

Dr. Sonja Amoser
SteinrieglstraÃe 286
3400 Weidlingbach

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