Excitation - inhibition

KP_PC k.p.collins at worldnet.att.net
Tue May 20 17:16:57 EST 2003


Hi Dag. Thanks for posting this. I'll have to read the article. More
be;pw.

"Dag Stenberg" <dag.stenberg at nospam.helsinki.fi.invalid> wrote in
message news:bacile$5vs$1 at oravannahka.helsinki.fi...
| Shu Y, Hasenstaub A, McCormick DA
| Turning on and off recurrent balanced cortical activity
| Nature 423(6937) : 288-93 (2003)
|
| The vast majority of synaptic connections onto neurons in the
cerebral
| cortex arise from other cortical neurons, both excitatory and
| inhibitory, forming local and distant 'recurrent' networks.
Although
| this is a basic theme of cortical organization, its study has been
| limited largely to theoretical investigations, which predict that
local
| recurrent networks show a proportionality or balance between
recurrent
| excitation and inhibition, allowing the generation of stable
periods of
| activity. This recurrent activity might underlie such diverse
operations
| as short-term memory, the modulation of neuronal excitability with
| attention, and the generation of spontaneous activity during sleep.
Here
| we show that local cortical circuits do indeed operate through a
| proportional balance of excitation and inhibition generated through
| local recurrent connections,

This =cannot be= because cortex, separated from activation arising
from sub-cortical regions cannot 'see' the external experiential
environment.

What goes on, instead, is as it's been discussed in AoK, Ap5 all
along. "Supersystem configuration" directed by the TD
E/I-minimization mechanisms, with continuous stochastic 'background'
inputs arising from the "reticular system' which, via TD E.I
minimization converges upon relatively-minimized cortical "loop
circuit" lengths.

"Of course", with respect to the latter, cross-talk amongst the
various cortical areas does occur.

It's just that, without the sub-cortical TD E.I-minimization
dynamics, cortex cannot even 'see' the external experiential
environmnet, let alone act upon it in intelligent ways.

| and that the operation of such circuits can
| generate self-sustaining activity that can be turned on and off by
| synaptic inputs. These results confirm the long-hypothesized role
of
| recurrent activity as a basic operation of the cerebral cortex.

"Of course", "recurrent activity [is] a basic operation of the
cerebral cortex".

"Of course".

It's just not everything.

I'll comment further after I've read the full article. [Don't know
when I'll be able to find a copy of the article.]

K. P. Collins





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