Re: Fwd: Hemispherectomy, partial brain transplant

From: Anders Sandberg (
Date: Mon Apr 03 2000 - 18:05:14 MDT

"Eliezer S. Yudkowsky" <> writes:

> Anders Sandberg wrote:
> >
> > "Eliezer S. Yudkowsky" <> writes:
> >
> > > So I got to thinking: What if Calvin is right, and our cortex has lots of
> > > small areas that are independently active and compete with each other to
> > > produce the overall thought? What if we could cut out a square inch of
> > > cortex (containing many complete active-areas) and implant it in another
> > > brain? That would leave the donor almost unchanged... but the recipient
> > > would have access to some of the thoughts and memories, and maybe even
> > > patterns of thought, of the donor, if the thoughts were strong enough to
> > > spread through the rest of the brain and become conscious.
> That wasn't me. That was Christopher J. Phoenix (I think - it's from memory).

I know it. But I see that I made the mistake of not properly changing
the originator. Mea culpa.
> > The loss of a square inch of cortex may not always be immediately
> > noticeable to the person losing it, but I wouldn't recommend
> > it. Calvin's ideas are not very accepted by the mainstream, and given
> > my limited understanding of them it is not obvious that the transplant
> > would work since the patterns are highly dependent on having the right
> > subcortical afferents - without their context they are meaningless.
> (FYI, there's an article on "columns" in my "MIT Encyclopedia of the
> Cognitive Sciences" and it's by William Calvin. I don't know about
> "accepted", but one would think that his theories are known to the mainstream.)

I recall that this only deals with the "normal" columns, the
hiearchical organisation of the neurons in the cortex into small
columns (microcolumns, hypercolumns and whatnot). This is not
controversial at all, and I think Calvin is indeed redgarded as an
expert on this. But his theory of self-replicating mosaics is not
widely believed.

> As far as I can tell, the primary problem with the theory is that if you
> transplanted a section of cortex, or a hemisphere, we wouldn't possess
> the technology to wire it into the rest of the brain. If severing the
> corpus callosum works as a surgical procedure, than switching the left
> hemispheres of two epileptic infants will still create a severed corpus
> callosum. Transplanting a square inch just gives a square inch that's
> connected only to itself and not to anything around it.

Yes, this is true. I didn't mention it because it was too obvious :-)

Anders Sandberg                                      Towards Ascension!                  
GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y

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