other recent science and bioengineering news

Allen L. Barker alb at datafilter.com
Sun Jun 20 23:59:32 EST 2004


Gray Matters: New Clues Into How Neurons Process Information
Source: University Of Southern California
Date: 2004-06-16

Researchers from USC and the Technion Medical School in Israel have
uncovered new clues into the mystery of the brain's ultra-complicated
cells known as neurons.

Their findings -- appearing in this month's issue of the journal
Nature Neuroscience -- contradict a widely accepted idea regarding the
"arithmetic" neurons use to process information.


"So, we now think of the neuron in terms of a two-layer model," Mel
said. "The first layer of processing occurs within separate dendritic
branches. Each branch independently adds up the inputs to that branch,
and then applies its own local thresholding non-linearity."

"In the second layer of processing," Mel added, "the results from all
the different branches are added together linearly at the cell body,
where they help to determine the cell's overall firing rate."

While the results are promising, the team is certain this is not the
final word on the pyramidal neuron.

"Undoubtedly, this is still too simple a model," Mel said. "But the
two-layer model is a better description, it seems, than to assume that
the neuron is simply combining everything linearly from
everywhere. That's clearly not what these data show."

According to Mel, one additional complexity that must eventually be
dealt with is that synaptic inputs arriving at the most remote part of
the neuron -- called the apical tuft -- may interact in subtle ways
with inputs arriving on the basal dendrites, closer to the cell body.

"We'd now like to see if we need to extend the two-layer model in to a
three-layer model," Mel said. "It may be that the basal and apical
dendrites each behave as we've been saying, but when they interact
with each other there's an additional nonlinear interaction that
occurs between them."

Mel emphasizes that the "arithmetic" rules he and his colleagues found
in pyramidal neurons may not apply to all neurons in the brain.



Quantum Dots See In The Dark: Nanodevices Promise Improved Night
Vision Goggles, Medical Sensors And More
Source: University Of Southern California
Date: 2004-06-15

Researchers at the University of Southern California and the
University of Texas at Austin have built and tested a device based on
nanostructures called quantum dots that can sensitively detect
infrared radiation in a crucial wavelength range.

The atmosphere is opaque to most infrared, but it is transparent for a
narrow "window" between 8 and 12 microns. Night vision goggles,
military target tracking devices and environmental monitors utilize
this range of wavelengths.

Anupam Madhukar, holder of the Kenneth T. Norris Chair in the USC
Viterbi School of Engineering with appointments in the departments of
materials science, biomedical engineering and physics, says "a class
of existing infrared detectors are based on what is called 'quantum
well' technology. But we have created a detector based on different
physics--quantum dot physics--that works at least as well and has the
potential to perform better."



Split personalities probed
Two personas trigger different brain networks.
9 January 2004


FDA Panel Approves Brain Implant to Control Depression
by Shankar Vedantam Tuesday June 15, 2004 at 08:44 PM


Nanoparticles Illuminate Brain Tumors For Days Under MRI
Source: Oregon Health & Science University
Date: 2004-05-31

PORTLAND, Ore. - A research team from Oregon Health & Science
University and the Portland Veterans Affairs Medical Center is
demonstrating some of the world's first clinical applications for
nanometer-size particles in the brain.

The OHSU scientists have shown that an iron oxide nanoparticle as
small as a virus can outline not only brain tumors under magnetic
resonance imaging, but also other lesions in the brain that may
otherwise have gone unnoticed, according to a study published in the
journal Neuropathology and Applied Neurobiology.


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Allen Barker

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