IUBio

machine brains

Ray Scanlon rscanlon at wsg.net
Sun Jan 24 20:08:25 EST 1999







Joe Kilner wrote in message <787me7$gcl$1 at pegasus.csx.cam.ac.uk>...
>
>Ray Scanlon wrote in message <36a73cc5.0 at ns2.wsg.net>...
>

>>The brain has all the neurons need to think and decide, we apply Occam's
>>Razor to exclude any need for soul (mind) or for the need of interaction
>>between soul and brain.
>>
>
>Oh!  I see!  We know what the criteria for thinking are now do we?  We know
>what is necessary to make a decision.  And we _know_ that the brain can
>fulfill these criteria!  Oh, in that case then you are right the soul does
>not need to interact with the brain at all.  If this is true then can you
>please tell me what thinking and deciding are?  And what do you need to do
>them?  And how _exactly_ do you *know* that you are right - especially if
>your answer is based on any of the science of the last few hundred years,
>nothing can ever be known from science - we can just have better or worse
>reasons to believe in it!


You ask two questions: 1. What is thinking and deciding, and 2. How do I
know I am right.

Good! Let's cut to the chase.

A set of one or more neurons that are simultaneously active is a
constellation. A series of constellations that are active in an unvarying
sequence (such as a melody) is a chain. A constellation that may or may not
follow another constellation is an association. Signals from a constellation
in the basal ganglia and/or the cerebellum is a motor program. A motor
program can be thought of as the pulses of air passing through the holes in
a roll in a player piano.

Thinking and deciding evolved in mammals with the appearance of the
reticular nucleus of the thalamus. This nucleus enfolds the thalamus as a
blanket. It (or rather the neurons that comprise it) functions by inhibiting
the relay neurons in the medial geniculate body (auditory system), lateral
geniculate body (visual system), ventral posterior medial-ventral posterior
lateral complex (somatosensory system), and the ventral anterior-ventral
lateral complex (motor programs proceeding from the basal ganglia and the
cerebellum).

Any frustration, failure, or body damage (pain) that follows a motor act is
a bad result. Any pleasure that follows a motor act is a good result.

When a bad result happens, recently active constellations have any
excitatory synapses they may have in the reticular nucleus of the thalamus
strengthened. If one or more of these constellations is active in the
future, the reticular nucleus of the thalamus will be excited. When this
happens signal energy and motor programs will be held up in the thalamus as
sketched out above. In the absence of incoming signal energy, constellations
in the neocortex will associate. Each active constellation will take part in
activating motor programs in the basal ganglia. This will continue as long
as
the reticular nucleus of the thalamus is excited. The mammal is thinking. If
one of the motor programs does not have a bad history, the reticular nucleus
of the thalamus will cease being active and the motor program will proceed
to the motor and pre-motor cortex. The mammal has decided.

When a good result happens, recently active constellations will have any
inhibitory synapses they may have in the reticular nucleus of the thalamus
strengthened. In the future these inhibitory synapses will be (in effect)
weighed against excitatory synapses to determine the condition of the
reticular nucleus of the thalamus.

In addition the brainstem has inhibitory synapses on the neurons of the
reticular nucleus of the thalamus. As time passes with the reticular nucleus
of the thalamus active, the pressure from the brainstem will build up until
it overcomes the activation from previous bad results. The reticular nucleus
of the thalamus will be inhibited and action will ensue. The results may be
bad but there will be action.

A rat hesitating before a piece of cheese and a mathematician working out a
theorem use exactly the same mechanisms.

This is thinking and decision.

The level of activity in the reticular nucleus of the thalamus is dependent
on the past history of bad and good and on the wiring constructed by the
DNA. If I have an active constellation, a thought, and the reticular nucleus
of my thalamus is inhibited, I know truth. This is how I know I am right and
it is how you know you are right. Thus there is room in the world for many
truths. There is also absolute truth as wired by the DNA.

This argument is best evaluated by a computer engineer who has had
experience in microprogramming and has a foundation in neuroscience, it is
both a partial  explanation of how the brain works and a partial description
of a machine brain.

Ray
Those interested in how the brain works might look at
www.wsg.net/~rscanlon/brain.html












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