Susanne Hoffmann, Leonie Baier, Frank Borina, Gerd Schuller, Lutz Wiegrebe and
Uwe Firzlaff (2008): Psychophysical and neurophysiological hearing thresholds
in the bat Phyllostomus discolor. J. Comp. Physiol. A 194(1), 39-47
Abstract: Absolute hearing thresholds in the spear-nosed bat Phyllostomus
discolor have been determined both with psychophysical and neurophysiological
methods. Neurophysiological data have been obtained from two different
structures of the ascending auditory pathway, the inferior colliculus and the
auditory cortex. Minimum auditory thresholds of neurons are very similar in
both structures. Lowest absolute thresholds of 0 dB SPL are reached at
frequencies from about 35 to 55 kHz in both cases. Overall behavioural
sensitivity is roughly 20 dB better than neural sensitivity. The behavioural
audiogram shows a first threshold dip around 23 kHz but threshold was lowest at
80 kHz (â10 dB SPL). This high sensitivity at 80 kHz is not reflected in the
neural data. The data suggest that P. discolor has considerably better absolute
auditory thresholds than estimated previously. The psychophysical and
neurophysiological data are compared to other phyllostomid bats and differences
are discussed.
URL: http://www.springerlink.com/content/05660v5416m72225/
For reprints please contact Susanne Hoffmann (Email:
Sven SchÃrnich and Lutz Wiegrebe (2008): Phase sensitivity in bat sonar
revisited. J. Comp. Physiol. A 194(1), 61-67.
Abstract: An echolocating bat produces echoes consisting of the convolution of
echolocation call and the impulse response (IR) of the ensonified object. A
crucial question in animal sonar is whether bats are able to extract this IR
from the echo. The bat inner ear generates a frequency representation of call
and echo and IR extraction in the frequency domain requires accurate analysis
of both magnitude and phase information. Previous studies investigating the
phase sensitivity of bats using a jitter paradigm reported a temporal acuity
down to 10 ns, suggesting perfect sonar phase representation. In a
phantom-target playback experiment, we investigate the perceptual phase
sensitivity of the bat Phyllostomus discolor using a novel approach: instead of
manipulating IR phase by changing IR delay (jitter paradigm), we randomized IR
phase and thus lengthened the IR over time, leaving the magnitude spectrum
unchanged. Our results show that phase sensitivity, as reflected in the
analysis of signal duration, appears to be much lower than phase sensitivity,
as reflected in the analysis of signal onset. The current data indicate that
different temporal aspects of sonar processing are encoded with very different
temporal resolution and thus an overall claim of âphase sensitivityâ as such
cannot be maintained.
URL: http://www.springerlink.com/content/6070mr5463545131/
For reprints please contact Sven SchÃrnich (Email:
Roger D. Santer, Yoshifumi Yamawaki, F. Claire Rind and Peter J. Simmons
(2008): Phonotactic response of female crickets on the Kramer treadmill:
methodology, sensory and behavioural implications. J. Comp. Physiol. A 194(1),
79-96.
Abstract: Since population-level variation in female mating preferences can
shape intraspecific communication systems within the context of sexual
selection it is essential to quantify these preferences and their sources of
variation. We calculated individual female response functions for four male
calling song traits in the field cricket Gryllus bimaculatus, by performing
untethered phonotaxis measurements on a spherical locomotor compensator (Kramer
treadmill). Firstly, we quantify the population-level sources of phonotactic
variation and correct for factors that adversely affect this measurement.
Secondly, we develop methodology for the characterisation of individual female
phonotactic response functions suitable for population-level analyses and
demonstrate the applicability of our method with respect to recent literature
on Orthopteran acoustic communication. Phonotaxis towards a preferred stimulus
on different occasions is highly repeatable, with lower repeatabilities away
from the most preferred signal traits. For certain male signal traits, female
preference and selectivity are highly repeatable. Although phonotactic response
magnitude deteriorated with age, preference functions of females remained the
same during their lifetimes. Finally, the limitations of measuring phonotaxis
using a spherical locomotor compensator are described and discussed with
respect to the estimation of the selectivity of female response.
URL: http://www.springerlink.com/content/a4u81m0731771272/
For reprints please contact L. Verburgt (Email:
Kind regards
Sonja Amoser
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