Luke Remage-Healey & Andrew H. Bass (2010): Estradiol interacts with an
opioidergic network to achieve rapid modulation of a vocal pattern
generator. J. Comp. Physiol. A, 196 (2), 137-146.
Abstract: Estrogens rapidly regulate neuronal activity within
seconds-to-minutes, yet it is unclear how estrogens interact with neural
circuits to rapidly coordinate behavior. This study examines whether
17-beta-estradiol interacts with an opioidergic network to achieve rapid
modulation of a vocal control circuit. Adult plainfin midshipman fish emit
vocalizations that mainly differ in duration, and rhythmic activity of a
hindbrain?spinal vocal pattern generator (VPG) directly establishes the
temporal features of midshipman vocalizations. VPG activity is therefore
predictive of natural calls, and ?fictive calls? can be elicited by
electrical microstimulation of the VPG. Prior studies show that
intramuscular estradiol injection rapidly (within 5 min) increases fictive
call duration in midshipman. Here, we delivered opioid antagonists near the
VPG prior to estradiol injection. Rapid estradiol actions on fictive calling
were completely suppressed by the broad-spectrum opioid antagonist naloxone
and the mu-opioid antagonist beta-funaltrexamine, but were unaffected by the
kappa-opioid antagonist nor-binaltorphimine. Unexpectedly, prior to
estradiol administration, all three opioid antagonists caused immediate,
transient reductions in fictive call duration. Together, our results
indicate that: (1) vocal activity is modulated by opioidergic networks,
confirming hypotheses from birds and mammals, and (2) the rapid actions of
estradiol on vocal patterning depend on interactions with a mu-opioid
modulatory network.
URL: http://www.springerlink.com/content/e74j874658572517/
For reprints please contact Luke Remage-Healey (Corresponding author; Email:
Simo Hemilä, Sirpa Nummela & Tom Reuter (2010): Anatomy and physics of the
exceptional sensitivity of dolphin hearing (Odontoceti: Cetacea). J. Comp.
Physiol. A, 196 (3), 165-179.
Abstract: During the past 50 years, the high acoustic sensitivity and the
echolocation behavior of dolphins and other small odontocetes have been
studied thoroughly. However, understanding has been scarce as to how the
dolphin cochlea is stimulated by high frequency echoes, and likewise
regarding the ear mechanics affecting dolphin audiograms. The characteristic
impedance of mammalian soft tissues is similar to that of water, and thus no
radical refractions of sound, nor reflections of sound, can be expected at
the water/soft tissue interfaces. Consequently, a sound-collecting
terrestrial pinna and an outer ear canal serve little purpose in underwater
hearing. Additionally, compared to terrestrial mammals whose middle ear
performs an impedance match from air to the cochlea, the impedance match
performed by the odontocete middle ear needs to be reversed to perform an
opposite match from water to the cochlea. In this paper, we discuss
anatomical adaptations of dolphins: a lower jaw collecting sound, thus
replacing the terrestrial outer ear pinna, and a thin and large tympanic
bone plate replacing the tympanic membrane of terrestrial mammals. The paper
describes the lower jaw anatomy and hypothetical middle ear mechanisms
explaining both the high sensitivity and the converted acoustic impedance
match.
URL: http://www.springerlink.com/content/b2652797833p3538/
For reprints please contact Sirpa Nummela (Email:
Martin Singheiser, Dennis T. T. Plachta, Sandra Brill, Peter Bremen, Robert
F. van der Willigen & Hermann Wagner (2010): Target-approaching behavior of
barn owls (Tyto alba): influence of sound frequency. J. Comp. Physiol. A,
196 (3), 227-240.
Abstract: We studied the influence of frequency on sound localization in
free-flying barn owls by quantifying aspects of their target-approaching
behavior to a distant sound source during ongoing auditory stimulation. In
the baseline condition with a stimulus covering most of the owls hearing
range (1?10 kHz), all owls landed within a radius of 20 cm from the
loudspeaker in more than 80% of the cases and localization along the azimuth
was more accurate than localization in elevation. When the stimulus
contained only high frequencies (>5 kHz) no changes in striking behavior
were observed. But when only frequencies from 1 to 5 kHz were presented,
localization accuracy and precision decreased. In a second step we tested
whether a further border exists at 2.5 kHz as suggested by optimality
models. When we compared striking behavior for a stimulus having energy from
2.5 to 5 kHz with a stimulus having energy between 1 and 2.5 kHz, no
consistent differences in striking behavior were observed. It was further
found that pre-takeoff latency was longer for the latter stimulus than for
baseline and that center frequency was a better predictor for landing
precision than stimulus bandwidth. These data fit well with what is known
from head-turning studies and from neurophysiology.
URL: http://www.springerlink.com/content/64t0608170545524/
For reprints please contact Martin Singheiser (Email:
Jan Clemens, Gerroth Weschke, Astrid Vogel & Bernhard Ronacher (2010):
Intensity invariance properties of auditory neurons compared to the
statistics of relevant natural signals in grasshoppers. J. Comp. Physiol. A,
196 (4), 285-297.
Abstract: The temporal pattern of amplitude modulations (AM) is often used
to recognize acoustic objects. To identify objects reliably, intensity
invariant representations have to be formed. We approached this problem
within the auditory pathway of grasshoppers. We presented AM patterns
modulated at different time scales and intensities. Metric space analysis of
neuronal responses allowed us to determine how well, how invariantly, and at
which time scales AM frequency is encoded. We find that in some neurons
spike-count cues contribute substantially (20?60%) to the decoding of AM
frequency at a single intensity. However, such cues are not robust when
intensity varies. The general intensity invariance of the system is poor.
However, there exists a range of AM frequencies around 83 Hz where intensity
invariance of local interneurons is relatively high. In this range, natural
communication signals exhibit much variation between species, suggesting an
important behavioral role for this frequency band. We hypothesize, just as
has been proposed for human speech, that the communication signals might
have evolved to match the processing properties of the receivers. This
contrasts with optimal coding theory, which postulates that neuronal systems
are adapted to the statistics of the relevant signals.
URL: http://www.springerlink.com/content/yqmqx3hg4533816p/
For reprints please contact Jan Clemens
Gary Marsat & Gerald S. Pollack (2010): The structure and size of sensory
bursts encode stimulus information but only size affects behavior. J. Comp.
Physiol. A, 196 (4), 315-320.
Abstract: Cricket ultrasound avoidance is a classic model system for
neuroethology. Avoidance steering is triggered by high-firing-rate bursts of
spikes in the auditory command neuron AN2. Although bursting is common among
sensory neurons, and although the detailed structure of bursts may encode
information about the stimulus, it is as yet unclear whether this
information is decoded. We address this question in two ways: from an
information coding point of view, by showing the relationship between
stimulus and burst structure; and also from a functional point of view by
showing the relationship between burst structure and behavior. We conclude
that the burst structure carries detailed temporal information about the
stimulus but that this has little impact on the behavioral response, which
is affected mainly by burst size.
URL: http://www.springerlink.com/content/10vn2134306150x3/
For reprints please contact Gerald S. Pollack (Email:
Hannah M. ter Hofstede, Elisabeth K. V. Kalko & James H. Fullard (2010):
Auditory-based defence against gleaning bats in neotropical katydids
(Orthoptera: Tettigoniidae). J. Comp. Physiol. A, 196 (5), 349-358.
Abstract: Neotropical katydids (Orthoptera: Tettigoniidae) are preyed on by
gleaning bats, which are known to use male calling songs to locate them. At
least one katydid species has been reported to stop singing in response to
bat echolocation calls. To investigate the relationship between this
behavioural defence and ecological and sensory factors, we surveyed calling
song characteristics, song cessation in response to the echolocation calls
of a sympatric gleaning bat (Trachops cirrhosus), and T-cell responses (an
auditory interneuron sensitive to ultrasound) in five katydid species from
Panamá. The two katydid species that stopped singing in response to bat
calls (Balboa tibialis and Ischnomela gracilis, Pseudophyllinae) also had
the highest T-cell spike number and rate in response to these stimuli. The
third pseudophylline species (Docidocercus gigliotosi) did not reliably
cease singing and had low T-cell spiking activity. Neoconocephalus affinis
(Copiphorinae) produced continuous calling song, possibly preventing males
from hearing the bat during singing, and did not show a behavioural response
despite high T-cell activity in response to bat calls. Steirodon
rufolineatum (Phaneropterinae) did not cease singing and differed in T-cell
activity compared to the other species. T-cell function might not be
conserved in katydids, and evidence for this idea is discussed.
URL: http://www.springerlink.com/content/c8436816240755x3/
For reprints please contact Hannah M. ter Hofstede (Email:
Marco Lugli (2010): Sounds of shallow water fishes pitch within the quiet
window of the habitat ambient noise. J. Comp. Physiol. A, 196 (6), 439-451
Abstract: The habitat ambient noise may exert an important selective
pressure on frequencies used in acoustic communication by animals. A
previous study demonstrated the presence of a match between the
low-frequency quiet region of the stream ambient noise (termed ?quiet
window?) and the main frequencies used for sound production and hearing by
two stream gobies (Padogobius bonelli, Gobius nigricans). The present study
examines the spectral features of ambient noise in very shallow freshwater,
brackish and marine habitats and correlates them to the range of dominant
frequencies of sounds used by nine species of Mediterranean gobies
reproducing in these environments. Ambient noise spectra of these habitats
featured a low-frequency quiet window centered at 100 Hz (stream,
sandy/rocky sea shore), or at 200 Hz (spring, brackish lagoon). The analysis
of the ambient noise/sound spectrum relationships showed the sound
frequencies matched the frequency band of the quiet window in the ambient
noise typical of their own habitat. Analogous ambient noise/sound frequency
relationships were observed in other shallow-water teleosts living in
similar underwater environments. Conclusions may be relevant to the
understanding of evolution of fish acoustic communication and hearing.
URL: http://www.springerlink.com/content/h7018812k6282173/
For reprints please contact Marco Lugli (Email:
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