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    A Butterfly Effect In The Brain Next time your brain plays tricks on you, you have an excuse: according to new research by UCL scientists published in the
    Message 1 of 1 , Jul 1, 2010
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      A Butterfly Effect In The Brain

      Next time your brain plays tricks on you,
      you have an excuse: according to new research
      by UCL scientists published in the journal
      Nature, the brain is intrinsically unreliable.

      This may not seem surprising to most of us,
      but it has puzzled neuroscientists for decades.
      Given that the brain is the most powerful
      computing device known, how can it perform
      so well even though the behaviour of its circuits is variable?

      A long-standing hypothesis is that the brain's
      circuitry actually is reliable and the
      apparently high variability is because your
      brain is engaged in many tasks simultaneously,
      which affect each other.

      It is this hypothesis that the researchers
      at UCL tested directly. The team a collaboration
      between experimentalists at the Wolfson Institute
      for Biomedical Research and a theorist, Peter
      Latham, at the Gatsby Computational Neuroscience
      Unit took inspiration from the celebrated
      butterfly effect from the fact that the flap
      of a butterfly's wings in Brazil could set off
      a tornado in Texas. Their idea was to introduce
      a small perturbation into the brain, the
      neural equivalent of butterfly wings, and
      ask what would happen to the activity in
      the circuit. Would the perturbation grow and
      have a knock-on effect, thus affecting the
      rest of the brain, or immediately die out?

      It turned out to have a huge knock-on effect.
      The perturbation was a single extra 'spike',
      or nerve impulse, introduced to a single
      neuron in the brain of a rat. That single
      extra spike caused about thirty new extra
      spikes in nearby neurons in the brain, most
      of which caused another thirty extra spikes,
      and so on. This may not seem like much, given
      that the brain produces millions of spikes
      every second. However, the researchers estimated
      that eventually, that one extra spike affected
      millions of neurons in the brain.

      "This result indicates that the variability
      we see in the brain may actually be due to
      noise, and represents a fundamental feature
      of normal brain function," said lead author
      Dr. Mickey London, of the Wolfson Institute
      for Biomedical Research, UCL.

      This rapid amplification of spikes means
      that the brain is extremely 'noisy' much,
      much noisier than computers. Nevertheless,
      the brain can perform very complicated tasks
      with enormous speed and accuracy, far faster
      and more accurately than the most powerful
      computer ever built (and likely to be built
      in the foreseeable future). The UCL researchers
      suggest that for the brain to perform so well
      in the face of high levels of noise, it must
      be using a strategy called a rate code. In a
      rate code, neurons consider the activity of
      an ensemble of many neurons, and ignore the
      individual variability, or noise, produced
      by each of them.

      So now we know that the brain is truly noisy,
      but we still don't know why. The UCL researchers
      suggest that one possibility is that it's the
      price the brain pays for high connectivity
      among neurons (each neuron connects to about
      10,000 others, resulting in over 8 million
      kilometres of wiring in the human brain).
      Presumably, that high connectivity is at
      least in part responsible for the brain's
      computational power. However, as the research
      shows, the higher the connectivity, the noisier
      the brain. Therefore, while noise may not be
      a useful feature, it is at least a by-product
      of a useful feature.

      Source: University College London - UCL
      ----------------------------------------------------------------------

      Article URL: http://www.medicalnewstoday.com/articles/193482.php
      Posted here for non-commercial purposes. This
      fulfills the criteria of the Fair Use statutes.
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