[Martin Taylor 2013.02.01.23.08]
[From Bill Powers (2013.02.01.1635 MST)]
Adam Matic 2013.1.31.2100 cet 00Rick Marken (2013.01.31.1100)
[…]
So my conclusion is that this paper, that is presumably
“supportive” of PCT is, at best, irrelevant to PCT and, at
worst, completely misleading about the nature of purposeful
(control)
behavior. In my estimation this paper is worth less than
nothing.AM: After the tone of your previous post, I expected something likethis, so
I went over the paper a few more times and… yeah… they don’t
look like
they understand control theory let alone PCT. There are really
no control
systems modeled, of any kind.BP: I ran across a paper about mice or rats using vibrissae(movable
whiskers) to sense the positions of things – didn’t save it, but
I think
the Saig et. al, paper is specifically about that kind of sensing.
The
two arms sweeping the hands back and forth until they touch
something are
like what the whiskers do.I concur with your judgement, and Rick's, about the relevance thispaper
to PCT. Zero, or perhaps a little less.
I don't know if the paper I attach is the paper to which you refer,
but it uses the mouse vibrissae. It’s one I had intended to bring up
in this forum anyway, for two reasons. Firstly, from time to time
questions have been raised about the computational abilities of
neurons, and this paper seems to show that individual dendrites do
their own computations, and secondly because the HPCT structure
shows only one place in which sensory and motor “input” come
together, and that is the comparator, where input comes from the
higher level outputs in the form of a reference signal. Could this
kind of dendritic computation be some element of comparator
function? It’s not easy for me to see how, but if that’s not it,
then there must be another place in some revised HPCT circuitry
where motor and sensory inputs are used in coordination.
Here's the abstract. The paper is attached.
Martin
--------------Nature 13 Decembeer 2012, 492, 247-251---------
-
& Jeffrey C. Magee
Active dendrites provide neurons with powerful processing
capabilities. However, little is known about the role of
neuronal dendrites in behaviourally related circuit
computations. Here we report that a novel global dendritic
nonlinearity is involved in the integration of sensory and
motor information within layer 5 pyramidal neurons during
an active sensing behaviour. Layer 5 pyramidal neurons
possess elaborate dendritic arborizations that receive
functionally distinct inputs, each targeted to spatially
separate regions1, 2 . At the
cellular level, coincident input from these segregated
pathways initiates regenerative dendritic electrical
events that produce bursts of action potential output3, 4 and circuits featuring
this powerful dendritic nonlinearity can implement
computations based on input correlation5 . To
examine this in vivo we recorded dendritic
activity in layer 5 pyramidal neurons in the barrel cortex
using two-photon calcium imaging in mice performing an
object-localization task. Large-amplitude, global calcium
signals were observed throughout the apical tuft dendrites
when active touch occurred at particular object locations
or whisker angles. Such global calcium signals are
produced by dendritic plateau potentials that require both
vibrissal sensory input and primary motor cortex activity.
These data provide direct evidence of nonlinear dendritic
processing of correlated sensory and motor information in
the mammalian neocortex during active sensation.Nonlinear dendritic integration of sensory and motor input during an
active sensing task
dendriticIntegration.pdf (856 KB)