k.p.collins at worldnet.att.net
Tue May 27 07:23:08 EST 2003
Looking for the V. B. Montcastle ref that John H. cited elsewhere in
this thread [Thanks, John], I came across the following URL:
Quoting from the article, which discusses the migration of neurons
during cortical development:
"This pattern of development has two major consequences. First, the
cortex develops in an inside-out pattern in which the earliest born
neurons are found in the deepest cortical layers while the later born
neurons move to the more superficial layers."
This "inside-out" pattern allows the development to derive in
whatever 'activation' occurs within the earlier-developed cells,
which substantiates the position that's been in AoK, Ap6 all along,
and which I discussed in the post to which this msg is in reply, and
whenever I've discussed "It's activation-dependence all the way down
[not turtles :-]" in the past here in b.n.
"Second, the radial glial hypothesis provides an explanation for the
columnar organization of the cortex."
I'm not 'familiar' with "the radial glial hypothesis", but it does
coincide with the role that's assigned to glia in NDT [AoK, Ap5] - as
an ionic-conductance facilitation substrate that's 'tuned' via neural
My thought when I read the above in the article was
"activation-dependent glial prototyping" - throw-away glia as
activation-dependent 'path-finders'. This would, of course, embody
any 'front-center orientation' stuff with respect to =any= activation
that's developmetally in-there, where, in early development. what
constitutes 'front-center' stuff is just 'average' activation.
It's =striking= how well this glial stuff would work via 'just'
activation-dependence. Even the 'columnar' extents can be accounted
for within the 'precursor' glial role's distributed activation
'equipotentiality'. Subsequently, as neural development follows the
lead of this glial activation-dependent stuff, the neuronal
activation would gradually take over, and, since, the rest of the
body's structure is also forming, the 'front-center orientation'
stuff of my previous post would definitely suffice to achieve the
final wiring up all along the neurons' ramifications, because, as is
quoted above, the later cortical neurons grow =through= the earlier
cortical neurons, thereby experiencing their activation as their
guiding 'light' - in a way that's reminiscent of heliotrophy in
I'll bet it's the same way at the subcortical 'end' too.
The article continues:
"Each group of progenitor cells within the ventricular zone gives
rise to a column of interrelated neurons above it. After the neurons
have taken their proper laminar positions, they develop
characteristic synaptic connections with nearby neurons as well as
more distant neurons in associated regions of the cortex."
Again, the 'front-center orientation' stuff of my previous post would
definitely suffice to achieve the final wiring up.
No 'turtles' :-]
The article continues, focusing on "protein" 'guides', but I expect
that these are just artifacts of the developmental growth.
The development =must= be tightly-integrated. The =only= thing that
can achieve such is activation-dependence.
If there were "protein" 'guides', they'd =still= have to be governed
by an activation-dependence, but just a different kind that went
through the Redundant 'step' of 'activating' the proteins =and=
guiding their distribution as 'guides'.
I've =never= seen the Biology do anything so inherently-Wasteful in
terms of the costs of encoding it nor the costs of implementing 'it'
Why do the same thing in two different ways when one of the ways is
built-right-into the early activation that's in-there anyway?
Hence my "=only= thing", above.
The protein stuff is just developmental artifact stuff.
The 'jaw-hanger' with respect to all of this is that, if it's so,
then developmental injuries can be the result of 'abnormal' fetal
movement restrictedness. I've heard, for instance, that California
has an elevated rate of Autistic briths. Could it be that something
like 'style consciousness' leads to restricted fetal movement in the
womb, and this throws 'front-center' activation-dependence off it's
mark? If so, the correlation would be heightened in pregancies
correlated with minimal exercise, but with 'high-style' [restrictive]
acoutrement ['sliming' clothing](?).
Let those fetuses 'dance'!
Anyway, I've 'let my guard down', a bit, in this msg because I
thought it was Fair to give folks insight into the Freedom with which
I 'Explore' Neuroscience.
My $5.00 [one-time :-] says it ain't "proteins".
[=Of course= I'm not 'ruling-out' chemically-induced [i.e.
Thalidamide] type stuff, but, come to think of it, that stuff must
also impact activation-dependence.]
It's 3-D energydynamics all the way down.
K. P. Collins
"Schmitd! Schmitd! Ve vill build a Shapel!"
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