[UACCESS-L] Fwd: [The vOICe] Carnegie Mellon Scientists Show How Brain Processes Sound

[David Poehlman <poehlman1@comcast.net>]

Begin forwarded message:

From: "Peter Meijer" <seeingwithsound@gmail.com>
Date: February 28, 2006 6:05:12 AM EST
To: seeingwithsound@freelists.org
Subject: [The vOICe] Carnegie Mellon Scientists Show How Brain  
Processes Sound
Reply-To: seeingwithsound@freelists.org

Hi All,

For your information. Appended is a Carnegie Mellon news
release that appeared a few days ago. Now just the optimal
code for visual sounds as well, please...

Best wishes,

Peter Meijer


Seeing with Sound - The vOICe
http://www.seeingwithsound.com/winvoice.htm


Carnegie Mellon Scientists Show How Brain Processes Sound.

Landmark Results Could Improve Devices from iPods to
Cochlear Implants.

PITTSBURGH - Scientists at Carnegie Mellon University
have discovered that our ears use the most efficient way
to process the sounds we hear, from babbling brooks to
wailing babies. These results represent a significant
advance in understanding how sound is encoded for
transmission to the brain, according to the authors,
whose work is published with an accompanying "News and
Views" editorial in the Feb. 23 issue of Nature.

The research provides a new mathematical framework for
understanding sound processing and suggests that our
hearing is highly optimized in terms of signal coding -
the process by which sounds are translated into
information by our brains - for the range of sounds we
experience. The same work also has far-reaching, long-
term technological implications, such as providing a
predictive model to vastly improve signal processing for
better-quality compressed digital audio files and
designing brain-like codes for cochlear implants, which
restore hearing to the deaf.

To achieve their results, the researchers took a
radically different approach to analyzing how the brain
processes sound signals. Abstracting from the neural code
at the auditory nerve, they represented sound as a
discrete set of time points, or a "spike code," in which
acoustic components are represented only in terms of
their temporal relationship with each other. That's
because the intensity and basic frequency of a given
feature are essentially "kernalized," or compressed
mathematically, into a single spike. This is similar to a
player piano roll that can reproduce any song by
recording what note to press when the spike code encodes
any natural sound in terms of the precise timings of the
elemental acoustic features. Remarkably, when the
researchers derived the optimal set of features for
natural sounds, they corresponded exactly to the patterns
observed by neurophysiologists in the auditory nerves.

"We've found that timing of just a sparse number of
spikes actually encodes the whole range of nature sounds,
including components of speech such as vowels and
consonants, and natural environment sounds like footsteps
in a forest or a flowing stream," said Michael Lewicki,
associate professor of computer science at Carnegie
Mellon and a member of the Center for the Neural Basis of
Cognition (CNBC). "We found that the optimal code for
natural sounds is the same as that for speech. Oddly
enough, cats share our own optimal auditory code for the
English language."

"Our work is the only research to date that efficiently
processes auditory code as kernalized spikes," said Evan
Smith, a graduate student in psychology at the CNBC.

Until now, scientists and engineers have relied on
Fourier transformations - initially discovered 200 years
ago - to separate and reconstitute parameters like
frequency and intensity as part of traditional sound
signal processing.

"Our new signal processing framework appears far more
efficient, effective and concise in conveying a rich
variety of natural sounds than anything else," Lewicki
said.

Smith and Lewicki's approach dissects sound based only on
the timing of compressed "spikes" associated with vowels
(like cat vocalizations), consonants (like rocks hitting
one another) and sibilants (ambient noise).

To gather sounds for their research, the scientists
traipsed through the woods and recorded cracking
branches, crunching leaves and wind rustling through
leaves before returning to the laboratory to decode the
information contained in this rich set of sounds. They
also discovered what they consider the most "natural"
sound: if they play back a random set of spikes, it
sounds like running water.

"We're very excited about this work because we can give a
simple theoretical account of the auditory code which
predicts how we could optimize signal processing to one
day allow for much more efficient data storage on
everything from DVDs to iPods," Lewicki said.

"For instance, if we could use a cochlear implant to
'talk' to the auditory nerve in a more natural way via
our discovered coding, then we could quite possibly
design implants that would convey sounds to the brain
that are much more intelligible," he said.

The authors' research, which combines computer science,
psychology, neuroscience and mathematics, is funded by
the National Institutes of Health and the National
Science Foundation.

The CNBC is dedicated to understanding the neural
mechanisms that give rise to cognitive processes,
including learning and memory, language and thought,
perception and attention, and planning and action. The
CNBC faculty includes researchers with primary and joint
appointments in the departments of Biological Sciences,
Computer Science, Psychology, Robotics and Statistics at
Carnegie Mellon; and Bioengineering, Mathematics,
Neurobiology, Neurology, Neuroscience, Psychiatry and
Psychology at the University of Pittsburgh.

See http://www.cnbc.cmu.edu for more information.

Source URL:
http://www.cmu.edu/PR/releases06/060223_sound.html

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