From: Anders Sandberg (asa@nada.kth.se)
Date: Mon Apr 20 1998 - 10:17:00 MDT
ChuckKuecker <ckuecker@mcs.net> writes:
> Imaging, as distinct from 'reading' or 'uploading' is already here in
> several forms. PET scans, MRI, and CT are well known, and resolution is
> increasing steadily.
The problem is that the current methods all have rather strong limits
to their resolution (PET is limited by the mean free path for
positrons, MRI by heating of tissue by changing magnetic fields and CT
by the risk of radiation damage). Of course, new methods might (more
likely, *will*) appear, but we cannot say for certain how good imaging
can get. I have a suspicion that it will never become scanning, since
it has to measure the brain from a significant macroscopic distance
(centimeters) while we want data on the micron scale.
> The problem I see here is: Does anyone really know how memories are stored -
> is it holographic, physical location, or wiring?
The current model is a bit of all three: memories are stored as
changes in synaptic efficacies across the brain, possibly also the
growth nof new dendrites and synapses. That means they are fairly
non-local, although they are more sensitive to damage to certain
subsystems than others.
> Is the brain serial or parallel in it's processing?
Parallel, at least when you look at the low-level systems of
perception, movement and memory (fairly natural when you have 10^100
independent neurons active together). High-level cognition might be
more serial, but it is not settled yet.
> How much of the brain's activity is electrical
> and how much is chemical, when it comes to actual thought?
They are the same. The signals that rush along neurons are
electrochemical processes where ions move in and out of the cell. At
synapses the signals release neurontransmittors that cause electric
changes in the postsynaptic cell. There are purely chemical processes
and signals, but they seem to act much slower than the electrochemical
signals and hence are unlikely to be part of normal thought.
> We are still in the infancy of learning exactly how the brain works...
Indeed. That makes it so fun to study!
-- ----------------------------------------------------------------------- Anders Sandberg Towards Ascension! asa@nada.kth.se http://www.nada.kth.se/~asa/ GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y
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