Persistent activity

Whenever I think about the recession and the stimulus package, I’m reminded of the phenomenon of working memory and persistent activity in the brain, which I’ve worked on in the past.  I’ll explain the connection at the end of the post. Working memory is the short term memory we use when we remember a phone number just long enough to call someone and then forget shortly afterward.  Neuroscientists have found neurons in the pre-frontal cortex of monkeys that are correlated with the memory.  So when you present the monkey a transient stimulus that it must remember, these neurons start firing  and remain activated until the memory is no longer needed.  This is a neural correlate of working memory.  This implies that there must be bistability (or multistability) in the firing state of a neuron.

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More on Feynman

It had been many years since I last read any books by or about Feynman.  Unfortunately, I never had the chance to hear him speak in person.  I also had never read the book version of “The character of physical law” before so there were several things that struck me after watching some of the lectures.  The first was that Feynman was extremely philosophical and cultured.  This was somewhat surprising because the mythology surrounding Feynman, promoted by his own autobiographies, is that he was the no-nonsense street-smart kid from Brooklyn who used common sense and cunning to outsmart the so-called intellectuals with highfalutin ideas.  I never fully bought into that myth but now  after watching three of the lectures I feel as if they can be completely dispelled.  Feynman was extremely intellectual and very interested in the humanities. He just disagreed with how they were being carried out and done at that time.

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Feynman’s “The Character of Physical Law”

Richard Feynman’s famous 1964 lecture series “The character of physical law“, is now available on the web curtesy of Bill Gates, who bought the rights.  For any of you who are uamiliar with Feynman, I would recommend watching the brilliant physicist and expositor at work.  There are seven lectures in total.  I watched the first, describing the law of grativation,  and the fifth on the distinction of past and future, where he gives a beautiful and clear explanation of entropy and the arrow of time.

Feynman also anticipates complexity theory in the fifth lecture.  He says that knowing the fundamental laws don’t help much in understanding complex phenomena like entropy.  There is a lot of analysis that must be done to get there.  He also talks about the hierachy of descriptions from the laws of elementary forces and particles all the way up to human concepts like beauty and hope.  He then says that he doesn’t believe either end of this spectrum or any of the steps in between are any more “closer to God”, i.e. more fundamental than any other.  He jokes that the people working on these very different fields should not have any animosity towards each other and that they’re all doing essentially the same thing, which is to try to relate the various levels of the hierarchy to each other.

Genetic basis for obesity

Olivia Judson’s blog on the New York Times today covers a topic that I have been very interested in the last five years.  I really liked her post because she is one of the few people in the popular press that has questioned the thrifty gene hypothesis for the recent obesity epidemic.  This theory proposed nearly 50 years ago is that we evolved during a time when food was scarce and famines were prevalent  so that we are genetically optimized to pack on as much weight as we can when food is available.  Hence, we are ill adapted to the modern age of plenty and as a result we are getting fat (as we should be).

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New director of NIH

Barack Obama has nominated Francis Collins to be the new Director of NIH. Here is the official announcement from the Secretary of HHS:

I am delighted to announce that, today, President Obama announced his intent to nominate Dr. Francis S. Collins to be Director of the National Institutes of Health.  Dr. Collins is one of our generation’s great scientific leaders.  A physician and geneticist, Dr. Collins served as Director of the National Human Genome Research Institute, where he led the Human Genome Project to completion. I hope the Senate acts quickly to confirm his nomination.

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Why consciousness?

If we believe in materialism then we must accept that the function of our brain is the collective action of the biological parts.  This doesn’t imply reductionism (i.e. just knowing the parts is enough), but it does imply that there is nothing beyond the laws of physics, chemistry and biology required for the operation of the brain.  Given that the brain is just some really big dynamical system, why then from a computational and evolutionary point of view is there consciousness?  I was criticized correctly in a previous post for not defining consciousness before talking about it. I will argue below that the definition of consciousness is intimately tied to its purpose but for now it suffices to work with the definition that consciousness is the sense of self awareness that I personally have.  I’m pretty sure you have it too but of course I can’t prove it.  For what I will discuss, it won’t matter if consciousness is an illusion or not.  I will focus on why in a purely materialistic world, say a computer simulation, would a being in that world composed entirely of interacting components (e.g. bits), have a sense of self awareness and spectate the world around them.

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