"Egan, Greg - Extra, The" - читать интересную книгу автора (Egan Greg)

empire began to make significant progress on the brain transplant problem.
Transplants between newborn Extras had been successful for decades. With
identical genes, and having just emerged from the very same womb (or from the
anatomically and biochemically indistinguishable wombs of two clone-sister
Extras), any differences between donor and recipient were small enough to be
overcome by a young, flexible brain.
However, older Extras - even those raised identically - had shown remarkable
divergences in many neural structures, and whole-brain transplants between them
had been found to result in paralysis, sensory dysfunction, and sometimes even
death. Gray was no neuroscientist, but he could understand roughly what the
problem was: Brain and body grow and change together throughout life, becoming
increasingly reliant on each other's idiosyncrasies, in a feed-back process
riddled with chaotic attractors - hence the unavoidable differences, even
between clones. In the body of a human (or an Extra), there are thousands of
sophisticated control systems which may include the brain, but are certainly not
contained within it, involving everything from the spinal cord and the
peripheral nervous system, to hormonal feedback loops, the immune system, and,
ultimately, almost every organ in the body. Over time, all of these elements
adapt in some degree to the particular demands placed upon them - and the brain
grows to rely upon the specific characteristics that these external systems
acquire. A brain transplant throws this complex interdependence into disarray -
at least as badly as a massive stroke, or an extreme somatic trauma.
Sometimes, two or three years of extensive physiotherapy could enable the
transplanted brain and body to adjust to each other - but only between clones of
equal age and indistinguishable lifestyles. When the brain donor was a model of
a likely human candidate - an intentionally overfed, under-exercised,
drug-wrecked Extra, twenty or thirty years older than the body donor - the
result was always death or coma.
The theoretical solution, if not the detailed means of achieving it, was
obvious. Those portions of the brain responsible for motor control, the
endocrine system, the low-level processing of sensory data, and so on, had to be
retained in the body in which they had matured. Why struggle to make the donor
brain adjust to the specifics of a new body, when that body's original brain
already contained neural systems fine-tuned to perfection for the task? If the
aim was to transplant memory and personality, why transplant anything else?
After many years of careful brain-function mapping, and the identification and
synthesis of growth factors which could trigger mature neurons into sending
forth axons across the boundaries of a graft, Gray's own team had been the first
to try partial transplants. Gray watched tapes of the operations, and was both
repelled and amused to see oddly shaped lumps of one Extra's brain being
exchanged with the corresponding regions of another's; repelled by visceral
instinct, but amused to see the seat of reason - even in a mere Extra - being
treated like so much vegetable matter.
The forty-seventh partial transplant, between a sedentary, ailing
fifty-year-old, and a fit, healthy twenty-year-old, was an unqualified success.
After a mere two months of recuperation, both Extras were fully mobile, with all
five senses completely unimpaired.
Had they swapped memories and "personalities"? Apparently, yes. Both had been
observed by a team of psychologists for a year before the operation, and their
behaviour extensively characterised, and both had been trained to perform