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Bioacoustic papers in Natureâââââ

Subject: Bioacoustic papers in Natureâââââ
From: "XIAO, Jianqiang" <>
Date: Thu, 25 Feb 2010 14:24:05 -0500
Nature 463 (18 February 2010)

Research Highlights
853 | doi:10.1038/463853a
Neurobiology: The science of silence
Neuron 65, 412–421 (2010)
Hearing a sound stop is just as important as hearing it start, but how
the auditory system processes the end of a sound has been unclear.
Michael Wehr and his colleagues at the University of Oregon in Eugene
recorded activity in the brains of rats while playing tones to the
animals. The researchers found that individual neurons respond to the
beginning of tones at certain frequencies but respond to the end of
tones at very different frequencies, so one neuron could not register
'on' and 'off' for the same tone.
The results suggest that the brain must integrate activity in separate
neurons to register the beginning and end of a sound.

Editor's Summary
A bone of echolocation
Bats are highly specialized mammals — they can all fly, and many use
echolocation to communicate and find prey. Work on a primitive fossil
bat Onychonycteris finneyi suggested that although it could fly, it
would not have been able to echolocate. Now a microcomputed tomography
study of 26 bat species shows that in bats that use larynx-generated
clicks to echolocate, the stylohyal bone in the throat is connected to
the tympanic bone in the ear region of the skull. This condition is
found in Onychonycteris, once again reopening basic questions about
the timing and the origin of flight and echolocation in the early
evolution of bats.

939-942 | doi:10.1038/nature08737
A bony connection signals laryngeal echolocation in bats
Nina Veselka, David D. McErlain, David W. Holdsworth, Judith L. Eger,
Rethy K. Chhem, Matthew J. Mason, Kirsty L. Brain, Paul A. Faure & M.
Brock Fenton
Echolocation is an active form of orientation in which animals emit
sounds and then listen to reflected echoes of those sounds to form
images of their surroundings in their brains. Although echolocation is
usually associated with bats, it is not characteristic of all bats.
Most echolocating bats produce signals in the larynx, but within one
family of mainly non-echolocating species (Pteropodidae), a few
species use echolocation sounds produced by tongue clicks. Here we
demonstrate, using data obtained from micro-computed tomography scans
of 26 species (n = 35 fluid-preserved bats), that proximal
articulation of the stylohyal bone (part of the mammalian hyoid
apparatus) with the tympanic bone always distinguishes laryngeally
echolocating bats from all other bats (that is, non-echolocating
pteropodids and those that echolocate with tongue clicks). In
laryngeally echolocating bats, the proximal end of the stylohyal bone
directly articulates with the tympanic bone and is often fused with
it. Previous research on the morphology of the stylohyal bone in the
oldest known fossil bat (Onychonycteris finneyi) suggested that it did
not echolocate, but our findings suggest that O. finneyi may have used
laryngeal echolocation because its stylohyal bones may have
articulated with its tympanic bones. The present findings reopen basic
questions about the timing and the origin of flight and echolocation
in the early evolution of bats. Our data also provide an independent
anatomical character by which to distinguish laryngeally echolocating
bats from other bats.

Editor's Summary
Growing for a song
Previous studies have demonstrated a correlation between structural
changes in the brain and sensory experience, but whether similar
changes accompany learning is uncertain. High-resolution two-photon in
vivo imaging of individual neurons in the song control nucleus HVC
(higher vocal centre) of juvenile zebra finches that were learning
adult song patterns suggests that learning does involve such changes.
Within 24 hours of learning their first song, the normally dynamic
dendritic spines in the HVC of the zebra finches become larger and
more stable, and synaptic activity is enhanced.

948-952 | doi:10.1038/nature08759;
Rapid spine stabilization and synaptic enhancement at the onset of
behavioural learning
Todd F. Roberts, Katherine A. Tschida, Marguerita E. Klein & Richard Mooney
Behavioural learning depends on the brain's capacity to respond to
instructive experience and is often enhanced during a juvenile
sensitive period. How instructive experience acts on the juvenile
brain to trigger behavioural learning remains unknown. In vitro
studies show that forms of synaptic strengthening thought to underlie
learning are accompanied by an increase in the stability, number and
size of dendritic spines, which are the major sites of excitatory
synaptic transmission in the vertebrate brain. In vivo imaging studies
in sensory cortical regions reveal that these structural features can
be affected by disrupting sensory experience and that spine turnover
increases during sensitive periods for sensory map formation. These
observations support two hypotheses: first, the increased capacity for
behavioural learning during a sensitive period is associated with
enhanced spine dynamics on sensorimotor neurons important for the
learned behaviour; second, instructive experience rapidly stabilizes
and strengthens these dynamic spines. Here we report a test of these
hypotheses using two-photon in vivo imaging to measure spine dynamics
in zebra finches, which learn to sing by imitating a tutor song during
a juvenile sensitive period. Spine dynamics were measured in the
forebrain nucleus HVC, the proximal site where auditory information
merges with an explicit song motor representation, immediately before
and after juvenile finches first experienced tutor song. Higher levels
of spine turnover before tutoring correlated with a greater capacity
for subsequent song imitation. In juveniles with high levels of spine
turnover, hearing a tutor song led to the rapid ( approximately 24-h)
stabilization, accumulation and enlargement of dendritic spines in
HVC. Moreover, in vivo intracellular recordings made immediately
before and after the first day of tutoring revealed robust enhancement
of synaptic activity in HVC. These findings suggest that behavioural
learning results when instructive experience is able to rapidly
stabilize and strengthen synapses on sensorimotor neurons important
for the control of the learned behaviour.



XIAO, Jianqiang, Ph.D.
Research Associate
Psychology Department
Rutgers University
152 Frelinghuysen Road
Piscataway, NJ 08854

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