How the connections inside bird brains work together

Date:
February 2, 2022
Source:
Nagoya University
Summary:
Physiologists have a furthered understanding of the bird neural
circuitry that allows them to distinguish where a specific sound
is coming from.

Their findings could help scientists understand the basics of
how mammalian brains compute the time difference between a single
sound arriving at each individual ear, known as 'interaural time
difference'.

This ability is an integral component of sound localization.



FULL STORY ========================================================================== Nagoya University physiologists have furthered understanding of the
bird neural circuitry that allows them to distinguish where a specific
sound is coming from. Their findings, published in the journal Science Advances, could help scientists understand the basics of how mammalian
brains compute the time difference between a single sound arriving at
each individual ear, known as 'interaural time difference'. This ability
is an integral component of sound localization.


========================================================================== "Animals can perform accurate interaural time difference detection
for sounds of a wide range of frequencies," explains Rei Yamada, who specializes in cell physiology at Nagoya University's Graduate School
of Medicine. The nerve circuitry for this process is so specialized that
the many branches extending from a single nerve cell, called dendrites,
receive a specific sound frequency from one or the other ear. But it's
not yet clear exactly how all of this works together to enable interaural
time difference detection.

Yamada and his colleague Hiroshi Kuba wanted to understand more about
this process. They conducted laser experiments on chicken brain slices
by stimulating excitatory receptors on a part of the brain responsible
for sound localization. This was followed by simulation experiments to
clarify the meaning of their initial findings.

They discovered that nerve junctions, called synapses, were particularly clustered at the ends of specialized long dendrites dedicated to
conducting signals from low-frequency sounds. Counterintuitively,
this clustering reduced the strength of signal transmission along the
length of the dendrite so that it was smaller by the time it reached the
nerve cell. This process, however, enabled the nerve cell to tolerate
intense inputs arriving through dendrites dedicated to each ear, thereby maintaining its ability to conduct the necessary time difference and
location computing activities.

"Many animals, including humans, use the time difference of a
sound reaching both ears as a clue for sound source localization,"
says Yamada. "We would like to examine whether the association we
found between neural function and structure is universally common
in other species. Expanding our research to mammalian brains will
be important to understand the basic principle of interaural time
difference detection that birds and animals have in common with humans." ========================================================================== Story Source: Materials provided by Nagoya_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Rei Yamada, Hiroshi Kuba. Dendritic synapse geometry optimizes
binaural
computation in a sound localization circuit. Science Advances,
2021; 7 (48) DOI: 10.1126/sciadv.abh0024 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220202111833.htm

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