Re: "New Cornell study suggests that mental processing is continuous, not like a computer."
- From: "Stephen Harris" <cyberguard-1048@xxxxxxxxx>
- Date: Tue, 05 Jul 2005 16:02:12 GMT
"Sean" <SPRThompson@xxxxxxxxx> wrote in message
news:1120576364.958127.155970@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> No kidding? *shocked*
>
This used to be debated since some neuronal processes appear to
be analog (building towards firing potential) whereas others were
thought to be digital: an overall hybrid process. I thought Spivey's
experiment was interesting because the level of demonstration was
more macrocosmic in the sense of larger than a molecular observation.
I was thinking of the article below in a discussion with Wolf Kirchmeir
about back-propagation modification from a more distant source.
http://brain.web-us.com/brain/digital_brain_the_extraordinary_.htm
"Taken together, Koch believes, these new insights into the capabilities of
the single neuron suggest the brain should really be viewed as a hybrid
computer, one that employs both digital pulses (between neurons) and analog
computations (within them). The brain, then, is quite unlike a digital
computer in its basic underpinnings. Even if the brain is built of hybrid
digital-analog neurons, it need not have any computational powers that are
utterly beyond those of a simple digital computer. But simulating such a
brain using hybrid digital-analog elements may take thousands of times
longer than it would take to simulate a brain built of the same number of
simple neurons, points out Douglas R. Hofstadter of the University of
Indiana. [SH: order transposed]
And the story gets still more involved. Koch notes that the conventional
idea that the timing of individual spikes is unimportant turns out to be
quite wrong. Researchers had generally supposed that the representation of
information in the brain depends essentially on the overall rate of firing
of the neurons. But experiments over the past few years have shown
conclusively that some cells in monkeys' brains can adjust the intervals
between spikes in increments as little as one hundredth of as second.
Moreover, the temporal patterns of spike activity across different neurons
is sometimes controlled with an even finer accuracy of about one thousandth
of a second. Contrary to the common wisdom, "the brain appears to care a
great deal about timing," Koch says.
These results raise a new question: what is the purpose of all of that very
precise neural timing? Koch points toward breaking research that may offer a
clue. Spikes, once initiated in a neuron, do not propagate only in the
"forward" direction--that is, toward the synapses that relay outgoing
messages. Rather, experiments on isolated brain tissue indicate that spikes
also move backwards, up the neuron's input branches.
The effect that these back-propagated spikes have on the active components
of the brain--if indeed the phenomenon occurs in intact animals-- is far
from clear. But a study published in the January 10, 1997 issue of Science
by Henry Markram of the Weizmann Institute for Science and his collaborators
suggests that back-propagated spikes can dramatically influence the way a
neuron processes an impulse. The precise order in which one spike arrives at
a synapse and another one back-propagates to the receiving neuron greatly
influences the subsequent strength of a synapse, Markram's group showed. If
the back-propagated spike arrives first, the synapse is weakened;
conversely, if the back-propagated spike arrives second, the synapse is
intensified."
SH: I read in a Bohm book on Quantum Physics that a continuous process can
be approximated by increasing the digital frequency; how the cartoons of
yesteryear simulated motion by moving faster than the eye could distinguish.
Thus a digital computer still might simulate analog biological behavior.
Daryl McCullough and Neil Rickert disputed a similar topic once upon a time.
Regards, Stephen
.
- Follow-Ups:
- Re: "New Cornell study suggests that mental processing is continuous, not like a computer."
- From: dan michaels
- Re: "New Cornell study suggests that mental processing is continuous, not like a computer."
- From: Sean
- Re: "New Cornell study suggests that mental processing is continuous, not like a computer."
- From: Stephen Harris
- Re: "New Cornell study suggests that mental processing is continuous, not like a computer."
- References:
- Prev by Date: Re: synchronous spatial activity in light-insensitive visual system
- Next by Date: Re: behaviorism vs internal states
- Previous by thread: Re: "New Cornell study suggests that mental processing is continuous, not like a computer."
- Next by thread: Re: "New Cornell study suggests that mental processing is continuous, not like a computer."
- Index(es):
Relevant Pages
|
Loading
