[tt] [x-risk] New map IDs the core of the human brain

[Eugen Leitl]

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From: arsen zahray <menkaur at gmail.com>
Date: Wed, 2 Jul 2008 06:02:01 +0300
To: existential at transhumanism.org
Subject: [x-risk] New map IDs the core of the human brain
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   [1]http://www.physorg.com/news134106650.html


   An international team of researchers has created the first complete
   high-resolution map of how millions of neural fibers in the human
   cerebral cortex -- the outer layer of the brain responsible for higher
   level thinking -- connect and communicate. Their groundbreaking work
   identified a single network core, or hub, that may be key to the
   workings of both hemispheres of the brain.


   The work by the researchers from Indiana University, University of
   Lausanne, Switzerland, Ecole Polytechnique Fédérale de Lausanne,
   Switzerland, and Harvard Medical School marks a major step in
   understanding the most complicated and mysterious organ in the human
   body.
   It not only provides a comprehensive map of brain connections (the
   brain "connectome"), but also describes a novel application of a
   non-invasive technique that can be used by other scientists to
   continue mapping the trillions of neural connections in the brain at
   even greater resolution, which is becoming a new field of science
   termed "connectomics."
   "This is one of the first steps necessary for building large-scale
   computational models of the human brain to help us understand
   processes that are difficult to observe, such as disease states and
   recovery processes to injuries," said Olaf Sporns, co-author of the
   study and neuroscientist at Indiana University.
   The findings appear in the journal PLoS Biology today (June 30).
   Co-authors include Patric Hagmann and Reto Meuli, University Hospital
   Center and University of Lausanne; Leila Cammoun and Xavier Gigandet,
   Ecole Polytechnique Fédérale de Lausanne; Van J. Wedeen, Massachusetts
   General Hospital and Harvard Medical Center; and Christopher J. Honey,
   IU.

   Until now, scientists have mostly used functional magnetic resonance
   imaging (fMRI) technology to measure brain activity -- locating which
   parts of the brain become active during perception or cognition -- but
   there has been little understanding of the role of the underlying
   anatomy in generating this activity. What is known of neural fiber
   connections and pathways has largely been learned from animal studies,
   and so far, no complete map of brain connections in the human brain
   exists.
   In this new study, a team of neuroimaging researchers led by Hagmann
   used state-of-the-art diffusion MRI technology, which is a
   non-invasive scanning technique that estimates fiber connection
   trajectories based on gradient maps of the diffusion of water
   molecules through brain tissue. A highly sensitive variant of the
   method, called diffusion spectrum imaging (DSI), can depict the
   orientation of multiple fibers that cross a single location. The study
   applies this technique to the entire human cortex, resulting in maps
   of millions of neural fibers running throughout this highly furrowed
   part of the brain.
   Sporns then carried out a computational analysis trying to identify
   regions of the brain that played a more central role in the
   connectivity, serving as hubs in the cortical network. Surprisingly,
   these analyses revealed a single highly and densely connected
   structural core in the brain of all participants.
   "We found that the core, the most central part of the brain, is in the
   medial posterior portion of the cortex, and it straddles both
   hemispheres," Sporns said. "This wasn't known before. Researchers have
   been interested in this part of the brain for other reasons. For
   example, when you're at rest, this area uses up a lot of metabolic
   energy, but until now it hasn't been clear why."
   The researchers then asked whether the structural connections of the
   brain in fact shape its dynamic activity, Sporns said. The study
   examined the brains of five human participants who were imaged using
   both fMRI and DSI techniques to compare how closely the brain activity
   observed in the fMRI mapped to the underlying fiber networks.
   "It turns out they're quite closely related," Sporns said. "We can
   measure a significant correlation between brain anatomy and brain
   dynamics. This means that if we know how the brain is connected we can
   predict what the brain will do."
   Sporns said he and Hagmann plan to look at more brains soon, to map
   brain connectivity as brains develop and age, and as they change in
   the course of disease and dysfunction.

References

   1. http://www.physorg.com/news134106650.html

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Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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