George Levy wrote:
[quoting Stathis Papaioannou]
> >I believe the level of detail required and the complexity of the
> required models is grossly underestimated.
> >Simply getting a 3D image of a brain down to electron microscopic
> detail, including all the synaptic
> >connections, would be an enormous task, and it probabaly wouldn't
> tell us any more about the mind
> >of the brain's owner than a picture of the books on a library
> shelf would tell us about the book contents.
> >I would bet more on mediaeval monks decoding the data on a DVD
> sent back in time than I would
> >bet on scientists decoding the contents of a human mind from
> cryopreserved brain sections.
>
>
>
>Let's cut through all this complexity and look at the functional equivalent
>of a neuron or a group of neuron. I want to distinguish between general
>architecture and particular architecture: general architecture will provide
>the framework within which any human brain could fit. Particular
>architecture is the architecture of a particular brain.
>
>1) General Architecture
>The general architecture of the brain is a hot research project of the
>scale and importance of the Genome Project and is currently being worked on
>by major laboratories. We could speed up the functional identification of
>neuronal groups or modules by using general architecture apriori knowledge
>we have about these modules. For example the architecture of the visual
>cortex is well defined. We could treat it as a module with minor variations
>from individual to individuals due to genetic differences such as Single
>Nucleotide Polymorphism SNP. SNPs. Very soon we shall have the genetic map
>of all the human SNPs. We shall also have the general architecture of the
>brain and all its nominal variations.
>
>2) Particular Architecture
>Imagine using an advanced version of a functional Magnetic Resonance
>Imaging (fMRI) device operating at the microscopic level on a slice of
>brain tissue. Without knowing exaclty what is in the brain tissue black
>box, it may be possible to identify their functional property and recreate
>these in silicon or any other convenient substrate. By the way, microscopic
>functional Magnetic Resonance Imaging is an existing technology that is
>currently being used. This is what I got using Google.
>
>Scholarly articles for functional magnetic resonance imaging microscop$
><http://scholar.google.com/scholar?hl=en&lr=&biw=793&sa=X&oi=scholart&q=functional+magnetic+resonance+imaging+microscop%24>
> The primate neocortex in comparative perspective using ...
><http://www.google.com/url?sa=X&oi=scholarr&start=0&num=3&q=http://www.anthropology.emory.edu/FACULTY/ANTJR/JHE_1999.pdf>
>- by Insel - 40 citations
>Neuroimaging and neuropathology in epilepsy: With ...
><http://www.google.com/url?sa=X&oi=scholarr&start=1&num=3&q=http://www.ingentaconnect.com/content/bsc/neu/1999/00000019/00000002/art00229>
>- by Nishio - 1 citations
>Evaluation by Contrast-Enhanced MR Imaging of the ...
><http://www.google.com/url?sa=X&oi=scholarr&start=2&num=3&q=http://www.kjronline.org/abstract/files/v02n0121.pdf>
>- by Jeong - 2 citations
>
>
>
>3) Combining General and Particular Architectures
>Fusing information to combine apriori knowledge of general architecture
>brain functions, and particular architecture data obtained from in situ
>functional measurements (e.g. fMRI), neurological and psychological
>measurements, as well as self-analysis, it may be possible to reconstruct a
>functional copy of the brain close enough as to be indinstinguishable from
>the original by the owner. How does the owner knows it is
>indistinguishable? This is a whole topic. He could for example do a series
>of partial substitutions to find out if it feels the same or not. For
>example, he could substitute in sequence the visual cortex, the auditory
>cortex, some of the motor functions....
>
>We may be closer to this goal than you think.
OK, I agree it is possible, and I'm glad nobody is insisting that just the
arrangement of neurons and their connections, such as could in theory have
been determined by a 19th century histologist, is enough information to
emulate a brain. I think we would need to have scanning resolution close to
the atomic level, and very detailed modelling of the behaviour of cellular
subsystems and components down to the same level. I don't know how long it
would take to achieve this, but I know that we are nowhere near it now. For
example, consider our understanding of schizophrenia, an illness which
drastically changes almost every aspect of cognition. For half a century we
have had drugs which ameliorate the psychotic symptoms patients with this
illness experience, and we have been able to determine which receptors these
drugs target. But despite decades of research, we still have no idea what
the basic defect in schizophrenia is, how the drugs work, or any clinically
useful investigation which helps with diagnosis. Although fMRI and PET scans
can show differences in cerebral blood flow compared to control subjects,
this is a secondary effect. The brains of schizophrenia sufferers, looked at
with any tools available to us, are essentially the same as normal brains.
In other words, a very subtle, at present undetectable, change in the brains
of these patients can cause gross cognitive and behavioural changes.
--Stathis Papaioannou
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Received on Sun Jul 10 2005 - 09:51:28 PDT