machine brains

Michael Edelman mje at mich.com
Mon Mar 8 09:21:19 EST 1999



Malcolm McMahon wrote:

> On Thu, 04 Mar 1999 08:34:04 -0500, Michael Edelman <mje at mich.com>
> wrote:
> >Is there in fact a clear distinction in digital computers? Other than the fact that we
> >know, a priori, that programs have to be loaded into computers, the distinction isn't
> >really clear. To an outside observer the program is a essentially description of the
> >state transitions in the digital computer. It's not clear what constitutes program and
> >what constitutes data
>
> But it _is_ pretty clear what constitutes wiring and what constitute
> transient electrical states in that wiring.

But that still doesn't tell us what's program and what's data. Changes in wiring may be
actual axonal growth, or it may be long-term potentiation of synapses. And axonal growth
may be repair, not memory change.

> >The brain similarly looks like an voltage-based analog device at the level of the
> >neuron, and a rate-responsive device at a higher level. At some very high level it
> >looks rather like an intelligent entity. Nonetheless it could theoretically be
> >described at any instant in time by a very large set of differential equations that
> >would predict what the voltages would be in the next millisecond.
>
> Here's the point though. Information stored in the brain isn't just
> electrical states, it goes, in fact, beyond chemical states into actual
> changes in the brain's layout. New synapses form while other disappear.
> You can give someone ECT and completely scramble the electrical state of
> the brain but only short term memories are affected.

ECT typically affects LTM as well, and I don't think it's accurate to say it "completely
scrambles the electrical state of the brain". It doesn't scramble it at all- rather, it
synchronizes it, much as occurs in a seizure- which is where the idea for ECT came from.

The point still holds that we cannot distinguish structure from content, or program from
storage, in the brain; is a particular "wiring" the matrix on which a memory can be stored,
or is it the memory itself?

> >> And, BTW, I still don't see any reason to believe consciousness is part
> >> of the mind.
> >
> >That strikes me more as a definition than as a statement regarding function. Does
> >conciousness exist? Well, we all certainly have the phenomenological experience of
> >conciousness, and we believe that others do as well, and all act in our day to day
> >lives as if we and others do. That certainly suggests not only that  conciousness is
> >an important enough phenomenon to study, but that it is possible to study it in
> >objective ways.
>
> But our only awareness of consciousness is inherently subjective. We
> can't perceive consciousness, only experience it.

There's that tricky "we" again. The point is that we all do experience conciousness. To
call it epiuphenomenal as some do is to define away an essential characterisitic of the
brain.

--
Michael Edelman     http://www.mich.com/~mje




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