a thinking brain

ray scanlon rscanlon at nycap.rr.com
Thu Jun 24 14:04:02 EST 2004

This is an outline of how a thinking machine might be constructed,
based on a speculative view of how the human brain works.

Some people are interested in how such a machine might be designed,
but most have other things in mind. Many are fascinated by the soul
(mind). The beauty of their thoughts overwhelms them. For starters, we
separate the material world from the immaterial world. Science attends
only to the material world. All talk of soul (mind) is irrelevant to a
scientific discussion of the brain.

A great many others engrossed in behavior. Their work is peripheral to
brain design. The brain creates fictive motor patterns, some of which
proceed to the motor cortex and end up as behavior. Brain design ends
at the motor cortex. A computer engineer has an academic interest in
application programs. He knows they exist, but they impinge on his
work only as he defines the instruction set. Similarly in brain
design, when given a particular behavior, the designer would like to
set down a particular neural circuit that would produce that behavior.

Another group that finds little interest in the details of brain
design are the mathematical logicians. Early on, this group rushed in.
They had isolated the rules of thought and knew how a brain must work.
The predicate calculus was a sufficient descriptor of thought. All
that was need was to mechanize the manipulative algebra of the
predicate calculus. This has been done, but the results are not

So, we do not address the religionists, the psychologists, and the
mathematical logicians.

The neuroscientists remain. Molecular biology exploded in the last
half-century. It continues to explode exponentially. The accumulation
of results is spectacular, unbelievable. But anyone, looking at the
field, sees only an incredible amount of work to be done. The genome
has been recorded. The story of life is written in the genome. All we
have to do is decode it and bring order to the ten thousand or so
kinds of proteins that make up any particular cell. Perhaps thirty
thousand proteins, if we look at all human cells. The neuron is just
such a cell.

The neuroscientist finds himself awash in data.  By preference, he
leaves brain design to others, except, at times, to bemoan the absence
of any overall theory of brain function. The Bell-Magendie law
(sensory in-motor out) is embroidered. The truth must lie there—but

Here is a highly speculative explanation of how the meat brain works:

Evolution has concentrated inhibitory neurons in the thalamic
reticular nucleus. This thin sheet of neurons surrounds the thalamus.
It has the capability of selectively halting visual signals on their
way to the cerebral cortex at the lateral geniculate body, auditory
signals at the medial geniculate, and somatosensory signals at the
ventral posterior lateral-ventral posterior medial nuclei. These are
traditionally presented as relay nuclei, but the flip side of relaying
is NOT relaying and that is exactly what they do under the influence
of the thalamic reticular nucleus.

When signal input to the cerebrum is halted at the thalamus, the
cerebrum is free to continue neural oscillations as started by
previous signal input. These oscillations are experienced by us, as
soul (mind), as free association (thoughts).

At the same time, the successive fictive motor programs initiated by
central pattern generators either by self-contained molecular activity
or by neural activity in the cerebrum cerebrum are elaborated in the
basal ganglia. These fictive motor programs are held up at the ventral
anterior-ventral lateral nuclei under the influence again of the
thalamic reticular nucleus.

Decision is effected by the thalamic reticular nucleus. A continuous
barrage of excitatory and inhibitory impulses arrive at the TRN. As
long as the excitatory inputs are in a majority the TRN inhibits the
relay nuclei, we, as soul (mind), experience hesitation. When the
inhibitory inputs become a majority the relay nuclei are disinhibited.
We, as soul (mind), experience decision. Thinking stops. The current
fictive motor program proceeds to the motor cortex and is executed.

By designing similar circuitry, we create a thinking machine brain.

No causal power is demanded of the soul (mind) and thus the criticism
of Descartes by the Princess Elizabeth is addressed. The brain thinks,
the soul (mind) experiences the thoughts.

Some things demand further explanation. The notion of a "fictive motor
program" asks to be developed. "Learning" is entire area that we have
not touched. The whole process of "deliberating" should be addressed. 
"Decision" requires a great expansion.


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