From: Jeff Davis (jdavis@socketscience.com)
Date: Tue Mar 23 1999 - 05:00:05 MST
Friends,
I'm cross-posting this to the cryonet and extropians list.
I've been thinking lately about brain damage. When exactly is identity
destroyed? I mean really obliterated?
Specifically, I'm wondering about the difference between loss of
information, and loss of ACCESS TO information. This last attributed to
the loss of higher-order function.
When a brain is damaged--I'm thinking here of strokes, traumatic injury,
brain tumors, and alzheimer's--certain structural changes take place.
Think of the spatial distribution of the damage.
Some of those changes presumably involve actual cell death. But how many
cells die, what fraction of the whole is that, how is the damage
distributed regionally/topologically, and what happens to the dead cell
bodies? (I assume fully necrotic cells undergo apoptosis and "digest"
themselves, the by-products being dispersed for either local or distant
consumption or disposal.) What of "scar tissue" and other structural
remnants?
Then too, what degree of brain damage is characterized by cell damage
without cell death--membrane or cytoskeletal damage/alteration; organelle
damage/reduced function--such that the cell still lives, but is not capable
of supporting the coordinated global activity characteristic of normal
brain function?(Does this happen, or am I describing a non-fact? I recall
that mitochondria sometimes suffer gradual degradation from, at least,
inherited defect.)
When a person is brain dead, is there actually a great lump of dead tissue
inside the skull (I don't think so), or does the absence of brain
waves--the flatline on the electroencephalograph that provokes the term
"persistant vegetative state"--only suffice to imply loss of global
function, but not large-scale cell death, maybe not even small-scale cell
death, or (here's the crux)maybe not nearly as much information loss as
we're inclined to think?
To what extent is the topology of damage responsible for disruptions of
neuronal firing patterns? Could the loss of memory or personality be due
not to the loss of the information, but to the inability of the organ to
fire that pattern, due to a disrupted firing path. Would the accumulation
of many small areas of damage, such as in the case of alzheimer's, so "damp
out" the spatially dynamic, electrochemical resonance of thought--of memory
and personality EXPRESSION--that the person seems to fade away? In a
man-made electronic system, a simple broken wire can result in a complete
system failure even though the actual structural deficit may be only an
infinitesimally small fraction of all the atoms of the system, and the
information deficit zero.
Are dementia et al victims really as far gone as we fear they are when we
view with dismay their varying degrees of vegetative-ness? Or is the
information there, but just not expressible?
Identity survival is central to cryonics. Some aspects of the (gradual)
process of identity deterioration provoke an interpretation of irreversible
loss. We look at them and say "They're gone." How valid is this? How
subject to reevaluation?
One final detail. I'm a strong believer in the "elegant design" of
natural systems. "Nature" squeezes as many uses out of any system
component as she can. (Please excuse the teleological and anthropomorphic
modes of expression.) Thus a local brain region with a specialized
function is likely to have multiple roles. In larger scale global
function--like memory or personality pattern storage and expression--it may
have a supporting but not a critical role. Thus limited local damage which
may cause striking loss of specific function may, as regards memory or
personality, have only a mild impact. In fact, let me repeat what has been
suggested before: that memory and personality may be broadly distributed
across the cortex and cerebellum (and elswhere?), that such distributed
expression is arguably inherently robust, and that these features strongly
suggest the importance of memory and personality to the individual and the
species (not to mention to cryonicists and extropians).
--------------------
In the process of writing this, I produced a typo: memeory, instead of
memory. Hmmmmmm.
Best, Jeff Davis
"Everything's hard till you know how to do it."
Ray Charles
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