Roderick A. Suthers, J. Martin Wild and Gisela Kaplan (2011): Mechanisms of
song production in the Australian magpie. J. Comp. Physiol. A, 197 (1),
45-59.
Abstract: Australian magpies (Gymnorhina tibicen) are notable for their
vocal prowess. We investigated the syringeal and respiratory dynamics of
vocalization by two 6-month-old males, whose songs had a number of adult
features. There was no strong lateral syringeal dominance and unilateral
phonation was most often achieved by closing the syringeal valve on the
contralateral side of the syrinx. Unlike other songbirds studied, magpies
sometimes used an alternative syringeal motor pattern during unilateral
phonation in which both sides of the syrinx are partially adducted and open
to airflow. Also, in contrast to most other songbirds, the higher
fundamental frequency during two-voice syllables was usually generated on
the left side of the syrinx. Amplitude modulation, a prominent feature of
magpie song, was produced by linear or nonlinear interactions between
different frequencies which may originate either on opposite sides of the
syrinx or on the same side. Pulse tones, similar to vocal fry in human
speech, were present in some calls. Unlike small songbirds, the fundamental
of the modal frequency can be as low as that of the pulse tone, suggesting
that large birds may have evolved pulse tones to increase acoustic
diversity, rather than decrease the fundamental frequency.
URL: http://www.springerlink.com/content/x63k5472625177x0/
For reprints please contact R. A. Suthers (email:
Sandra Wohlgemuth, Astrid Vogel & Bernhard Ronacher (2011): Encoding of
amplitude modulations by auditory neurons of the locust: influence of
modulation frequency, rise time, and modulation depth. J. Comp. Physiol. A,
197 (1), 61-74.
Abstract: Using modulation transfer functions (MTF), we investigated how
sound patterns are processed within the auditory pathway of grasshoppers.
Spike rates of auditory receptors and primary-like local neurons did not
depend on modulation frequencies while other local and ascending neurons had
lowpass, bandpass or bandstop properties. Local neurons exhibited broader
dynamic ranges of their rate MTF that extended to higher modulation
frequencies than those of most ascending neurons. We found no indication
that a filter bank for modulation frequencies may exist in grasshoppers as
has been proposed for the auditory system of mammals. The filter properties
of half of the neurons changed to an allpass type with a 50% reduction of
modulation depths. Contrasting to reports for mammals, the sensitivity to
small modulation depths was not enhanced at higher processing stages. In
ascending neurons, a focus on the range of low modulation frequencies was
visible in the temporal MTFs, which describe the temporal locking of spikes
to the signal envelope. To investigate the influence of stimulus rise time,
we used rectangularly modulated stimuli instead of sinusoidally modulated
ones. Unexpectedly, steep stimulus onsets had only small influence on the
shape of MTF curves of 70% of neurons in our sample.
URL: http://www.springerlink.com/content/p876828k3wg25066/
For reprints please contact Bernhard Ronacher (email:
Daniela Trobe, Richard Schuster & Heiner Römer (2011): Fast and reliable
decisions for a dynamic song parameter in field crickets. J. Comp. Physiol.
A, 197(1), 131-135.
Abstract: We investigated the choice of female crickets for a dynamic song
parameter (chirp rate) on a walking compensator, and the underlying neuronal
basis for the choice in the form of discharge differences in the pair of
AN1-neurons driving the phonotactic steering behaviour. Our analysis reveals
that decisions about chirp rate in a choice situation are made fast and
reliably by female crickets. They steered towards the higher chirp rate
after a delay of only 2.2?6 s, depending on the rate difference between the
song alternatives. In this time period, the female experienced only one to
two additional chirps in the song model with the higher rate. There was a
strong correlation between the accumulated AN1 discharge difference and the
amount of steering towards the side with the stronger response.
URL: http://www.springerlink.com/content/h81p856760478714/
For reprints please contact Heinrich Römer (email:
Kind regards
Sonja
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Dr. Sonja Amoser
Steinrieglstraße 286
3400 Weidlingbach
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