From: Grant Callaghan (grantc4@hotmail.com)
Date: Wed 12 Mar 2003 - 21:49:48 GMT
Bridging the Gaps Between Neuron, Brain and Behavior
with Neurodynamics
Walter J Freeman
Department of Molecular & Cell Biology
University of California, Berkeley CA 94720-3200
http://sulcus.berkeley.edu
Abstract:
Brain systems operate on many levels of
organization, each with its own scales of time
and space. Dynamics is applicable to every
level, from the atomic to the molecular, and
from macromolecular organelles to the neurons
into which they are incorporated. In turn the
neurons form populations; they form systems,
and so on to an embodied brain interacting
intentionally with its environment. Each level
is "macroscopic" to the one below it and
"microscopic" to the one above it. Among the
most difficult tasks are those of conceiving and
describing the exchanges between levels,
seeing that the scales of time and distance are
incommensurate, and that causal inference is
far more ambiguous between than within
levels. That holds for the relation of action
potentials from microelectrodes to whole brain
activity seen with new techniques for brain
imaging: fMRI and PET. A new recourse is
to conceive, identify and model an intervening
"mesoscopic" level, which is a local self-organizing
neural population. Its characteristic
activities consist of 'spontaneous' action
potentials and EEG dendritic activity.
Mesoscopic neurodynamics gives a clear
understanding of self-organized chaotic
patterns of neural activity in primary sensory
areas when significant stimuli arrive. These
patterns are created with each sniff, glance, or
movement of the head and hands. They are
triggered by sensory input, but they are not the
result of information processing, and they are
not representations of stimuli. They are
manifestations of the way in which brains make
and test hypotheses. The patterns show that
brains do not take information into themselves.
They formulate expectations as hypotheses and
test them by taking action into the
environment. They are not data-driven; they
are hypothesis-driven, and all that they can
know is what hypotheses were tested, and
what the results of the tests were.
Freeman WJ (2001) How Brains Make Up
Their Minds. New York: Columbia
University Press.
Grant
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