Matthew E. Jackson, Navdeep S. Asi & James H. Fullard (2010): Auditory
sensitivity and ecological relevance: the functional audiogram as modelled
by the bat detecting moth ear. J. Comp. Physiol. A 196 (7), 453-462.
Abstract: Auditory sensitivity has often been measured by identifying
neural threshold in real-time (online) which can introduce bias in the
audiograms that are produced. We tested this by recording auditory nerve
activity of the notodontid moth Nadata gibbosa elicited by bat-like
ultrasound and analysing the response offline. We compared this audiogram
with a published online audiogram showing that the bias introduced can
result in a difference in the audiogram shape. In the second part of our
study we compared offline audiograms using spike number as threshold with
others that used spike period and stimulus/spike latency, variables that
have been suggested as providing behaviourally functional criteria. These
comparisons reveal that functional audiograms are more flatly tuned than
simple spike audiograms. The shapes of behavioural audiograms are discussed
in the context of the selection pressure that maintains their shape, bat
predation. Finally, we make predictions on the distance from bats at which
notodontid moths use negative phonotaxis or the acoustic startle response.
URL: http://www.springerlink.com/content/h83575u270142v21/
For reprints please contact M. E. Jackson (email:
Miriam Wolf, Maike Schuchmann & Lutz Wiegrebe (2010): Localization
dominance and the effect of frequency in the Mongolian Gerbil, Meriones
unguiculatus. J. Comp. Physiol. A 196 (7), 463-470.
Abstract: Due to its good low-frequency hearing, the Mongolian Gerbil
(Meriones unguiculatus) has become a well-established animal model for
human hearing. In humans, sound localization in reverberant environments is
facilitated by the precedence effect, i.e., the perceptual suppression of
spatial information carried by echoes. The current study addresses the
question whether gerbils are a valid animal model for such complex spatial
processing. Specifically, we quantify localization dominance, i.e., the
fact that in the context of precedence, only the directional information of
the sound which reaches the ear first dominates the perceived position of a
sound source whereas directional information of the delayed echoes is
suppressed. As localization dominance is known to be stimulus-dependent, we
quantified the extent to which the spectral content of transient sounds
affects localization dominance in the gerbil. The results reveal that
gerbils show stable localization dominance across echo delays, well
comparable to humans. Moreover, localization dominance systematically
decreased with increasing center frequency, which has not been demonstrated
in an animal before. These findings are consistent with an important
contribution of peripheral-auditory processing to perceptual localization
dominance. The data show that the gerbil is an excellent model to study the
neural basis of complex spatial-auditory processing.
URL: http://www.springerlink.com/content/w3668645k7534084/
For reprints please contact Lutz Wiegrebe (email:
Mark A. Bee, Christophe Micheyl, Andrew J. Oxenham & Georg M. Klump (2010):
Neural adaptation to tone sequences in the songbird forebrain: patterns,
determinants, and relation to the build-up of auditory streaming. J. Comp.
Physiol. A 196 (8), 543-557.
Abstract: Neural responses to tones in the mammalian primary auditory
cortex (A1) exhibit adaptation over the course of several seconds.
Important questions remain about the taxonomic distribution of multi-second
adaptation and its possible roles in hearing. It has been hypothesized that
neural adaptation could explain the gradual “build-up” of auditory stream
segregation. We investigated the influence of several stimulus-related
factors on neural adaptation in the avian homologue of mammalian A1 (field
L2) in starlings (Sturnus vulgaris). We presented awake birds with
sequences of repeated triplets of two interleaved tones (ABA-ABA-…) in
which we varied the frequency separation between the A and B tones (ΔF),
the stimulus onset asynchrony (time from tone onset to onset within a
triplet), and tone duration. We found that stimulus onset asynchrony
generally had larger effects on adaptation compared with ΔF and tone
duration over the parameter range tested. Using a simple model, we show how
time-dependent changes in neural responses can be transformed into
neurometric functions that make testable predictions about the dependence
of the build-up of stream segregation on various spectral and temporal
stimulus properties.
URL: http://www.springerlink.com/content/3244565582t64018/
For reprints please contact M. A. Bee (email:
Megan D. Gall & Jeffrey R. Lucas (2010): Sex differences in auditory
filters of brown-headed cowbirds (Molothrus ater). J. Comp. Physiol. A 196
(8), 559-567.
Abstract: Receiver sensory abilities can be influenced by a number of
factors, including habitat, phylogeny and the selective pressure to acquire
information about conspecifics or heterospecifics. It has been hypothesized
that brood-parasitic brown-headed cowbird (Molothrus ater) females may
locate or determine the quality of potential hosts by eavesdropping on
their sexual signals. This is expected to produce different sex-specific
pressures on the auditory system to detect conspecific and heterospecific
acoustic signals. Here, we examined auditory filter shape and efficiency,
which influence the ability to resolve spectral and temporal information,
in males and females at center frequencies of 2, 3 and 4 kHz. We found that
overall, cowbirds had relatively wide filters (lsmean ± SE: 619.8 ± 41.6
Hz). Moreover, females had narrower filters (females: 491.4 ± 66.8, males:
713.8 ± 67.3 Hz) and greater filter efficiency (females: 59.0 ± 2.0,
males: 69.8 ± 1.9 dB) than males. Our results suggest that the filters of
female cowbirds may allow them to extract spectral information from
heterospecific vocalizations. The broader auditory filters of males may
reflect limited spectral energy in conspecific vocalizations in this
frequency range, and hence, weaker selection for high resolution of
frequency in the range of 2-4 kHz.
URL: http://www.springerlink.com/content/03676205q33q615n/
For reprints please contact M. D. Gall (email:
Kevin Christie, Johannes Schul & Albert S. Feng (2010): Phonotaxis to
male’s calls embedded within a chorus by female gray treefrogs, Hyla
versicolor. J. Comp. Physiol. A 196 (8), 569-579.
Abstract: During the reproductive season, male Hyla versicolor produce
advertisement calls to attract females. Females exhibit phonotaxis and
approach the individual callers, resulting in amplexus. For frogs that call
from dense choruses, the extent to which and the range from which a male’s
advertisement call within a chorus can be heard by a receptive female
leading to phonotaxis is unclear. We investigated females’ responses to
natural choruses in the field and found that they were attracted and showed
directed orientation to breeding choruses at distances up to 100 m. To
assess the role of acoustic cues in the directed orientation, we conducted
acoustic playback experiments in the laboratory using conspecific call and
noise as stimuli, as well as chorus sounds (that contained calls from a
focal male) recorded at various distances, all played at naturalistic
intensities. Using two response metrics (females’ normalized response
times and their phonotaxis trajectories) we found that, unlike the field
experiments, females oriented and were attracted to chorus sounds from 1 to
32 m only, but not from >32 m, or to band-limited noise. Possible reasons
for the observed difference in phonotaxis behavior in the two experimental
conditions were discussed.
URL: http://www.springerlink.com/content/l5711702v70l2346/
For reprints please contact K. Christie (email:
Melissa L. Caras, Eliot Brenowitz & Edwin W. Rubel (2010): Peripheral
auditory processing changes seasonally in Gambel’s white-crowned sparrow.
J. Comp. Physiol. A 196 (8), 581-599.
Abstract: Song in oscine birds is a learned behavior that plays important
roles in breeding. Pronounced seasonal differences in song behavior and in
the morphology and physiology of the neural circuit underlying song
production are well documented in many songbird species. Androgenic and
estrogenic hormones largely mediate these seasonal changes. Although much
work has focused on the hormonal mechanisms underlying seasonal plasticity
in songbird vocal production, relatively less work has investigated
seasonal and hormonal effects on songbird auditory processing, particularly
at a peripheral level. We addressed this issue in Gambel’s white-crowned
sparrow (Zonotrichia leucophrys gambelii), a highly seasonal breeder.
Photoperiod and hormone levels were manipulated in the laboratory to
simulate natural breeding and non-breeding conditions. Peripheral auditory
function was assessed by measuring the auditory brainstem response (ABR)
and distortion product otoacoustic emissions (DPOAEs) of males and females
in both conditions. Birds exposed to breeding-like conditions demonstrated
elevated thresholds and prolonged peak latencies when compared with birds
housed under non-breeding-like conditions. There were no changes in DPOAEs,
however, which indicates that the seasonal differences in ABRs do not arise
from changes in hair cell function. These results suggest that seasons and
hormones impact auditory processing as well as vocal production in wild
songbirds.
URL: http://www.springerlink.com/content/c6477573020rvrx2/
For reprints please contact E. W. Rubel (email:
Kind regards
Sonja Amoser
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Dr. Sonja Amoser
Steinrieglstraße 286
3400 Weidlingbach
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