On Sat, Apr 01, 2000 at 01:39:58AM -0500, EvMick@aol.com wrote:
>
> How far are we today from being able to keep a "naked" brain alive?
>
> To put it another way...how far away is a true cyborg?
>
> Not knowing anything about anything...but it seems to me that brains would be
> "relatively" easy to maintain....being made of only one (?) or two kinds of
> cells it's nutrient requirements must be simplier than that of a whole
> body....
The nutrient requirements of a whole body are not exactly simple. I was
once involved in the preparation of TPN (total parenteral nutrition)
bags for patients who were too ill to digest food; TPN is a rich,
creamy emulsion that can be perfused through a vein and contains about
the minimum necessary to keep you alive -- vitamins, ions, glucose,
trilgycerides, and a load of other stuff. It tends to be unstable --
use within six hours -- and has to be prepared in a clean room with
aseptic technique (you really _don't_ want to inject bacteria into
someone on TPN!).
At the other end of the cycle, you need a kidney and liver. I suppose a
dialysis machine would do instead, but that has its own problems (like,
potloads of dialysis fluid being required on an ongoing basis). And the
liver problem is more serious; keep recirculating blood through your
disembodied brain and it'll poison itself with its own waste metabolites
unless you've got a whole bunch of liver cells filtering the crap out of
it. The nearest thing to an artificial liver we're likely to see in the
next decade will be an external support column with a bunch of hepatocytes
(hopefully differentiated from clonal embryonic stem cells) growing in it.
Next, you need oxygenation and perfusion and circulation. This is
distinctly non-trivial, without a heart and lungs; we have machines to
do it in operating theatres, but they tend to knock the hell out of the
erythrocytes and need a constant dribble of anticoagulants to keep from
clogging up. And then there's haematopoeisis -- all your erythrocytes (red
blood cells) die by 14 days, so you need to produce a constant supply of
fresh blood. So either you need bone marrow, or your brain is going to
be queueing up at the blood bank right behind Dracula.
The brain has sod-all immune response. So you need to keep the whole
thing in a clean-room environment like unto a chip fab line -- operating
theatres are _much_ too dirty for this sort of job.
Finally, there's sensory hook-up. We are nowhere near being able to
give someone artificial vision (at any level much better than being
able to distinguish night from day). Nor do we know how to hook up the
various cranial nerves to a vocoder. Your disembodied brain is, in fact,
going to be in sensory deprivation hell -- until it succumbs to a passing
antibiotic-resistant infection, which will happen sooner rather than later
(because of all the crap we're having to ferry in to keep it alive).
The best life-support system for a human brain today is still a working
human body. And I don't see this situation changing in less than one
decade. Without spinal regeneration and full-body cloning, or much better
prostheses with working neural control interfaces and sensory feedback, I
can't see any medical demand for the Donovan's Brain treatment. (And I
expect those prostheses not to show up -- it's looking right now as if
it's a race between bionics and regeneration, and regeneration is
winning.)
-- Charlie (one-time Pharmacist) Stross
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