[From Bjorn Simonsen (2007.07.04,23:00 EUST)]
I must just inform you about David H. Hubel: Eye, Brain, and Vision, a book
I am reading these days. It is not a book from this year, it's from 1988.
But it is really informative for me (many of you have maybe read it before),
The reason I will inform you is the way it explains the central nervous
system. I will not copy any graphs, but here are two explaining texts. The
first I think is common in many books, but it is the first time I have read
the second text in a neurobiological book.
"Many parts of the central nervous system are organized in successive
platelike stages. A cell in one stage receives many excitatory and
inhibitory inputs from previous stage and send outputs to many cells at next
stage. ..."
"We also need to qualify our model with respect to direction of information
flow. The prevailing direction in our diagram is obviously from left to
right, from input to output, but in almost every case in which information
is transformed from one stage to the next, reciprocal connections feed
information back from one stage to the first. (We can sometimes guess what
such feedback might be useful for, but in almost no case do we have incisive
understanding)."
bjorn
[From Rick Marken (2007.07.04.2320)]
Bjorn Simonsen (2007.07.04,23:00 EUST)--
I must just inform you about David H. Hubel: Eye, Brain, and Vision, a book
I am reading these days. It is not a book from this year, it's from 1988.
But it is really informative for me (many of you have maybe read it before),
I haven't read it. But I think that Hubel's work with Torsten Wiesel
on receptive fields got pretty close to the PCT view of perception. I
use the receptive field work to illustrate the PCT idea of perception
as a neural signal that is a function of many lower level sensory
inputs. The main difference I see between the Hubel/Wiesel concept of
a receptive field and the PCT concept of a perceptual function is that
that Hubel/Wiesel saw the receptive field as a binary device; maximum
response meant the field's input pattern was present; no response
meant the pattern was not present. So the receptive field was seen as
a pattern detector and the neural signal was either firing (indicating
pattern present) or not. The PCT view is that the neural output of a
perceptual function (which is what a receptive field is) is a
continuous variable. So the rate of firing from a receptive field
would represent the state of the perceptual variable. If the
perception were of the orientation of a line then rate of firing might
indicate the angle of the line with respect to vertical, or something
like that.
\
"Many parts of the central nervous system are organized in successive
platelike stages. A cell in one stage receives many excitatory and
inhibitory inputs from previous stage and send outputs to many cells at next
stage. ..."
Yes, Hubel and Wiesel also had the idea of a hierarchy of perception,
which they noticed as they planted their electrodes in higher and
higher level cells (farther and farther from the sensory surface). So
they found receptive fields that they called simple (responded to a
light being there or not -- sounds like intensity level to me), then
complex (only certain shapes would do -- sounds like configuration)
and hyper complex (only certain shapes that move -- transition).
"We also need to qualify our model with respect to direction of information
flow. The prevailing direction in our diagram is obviously from left to
right, from input to output, but in almost every case in which information
is transformed from one stage to the next, reciprocal connections feed
information back from one stage to the first. (We can sometimes guess what
such feedback might be useful for, but in almost no case do we have incisive
understanding)."
I think this is internal feedback (looping back of neural signals in
the nervous system) which really has nothing important to do with PCT;
the feedback in PCT goes through the behaving system's environment.
Best
Rick
···
--
Richard S. Marken PhD
Lecturer in Psychology
UCLA
rsmarken@gmail.com
[From Bjorn Simonsen (2007.07.05,08:55 EUST)]
from Rick Marken (2007.07.04.2320)
I haven't read it. But I think that Hubel's work with Torsten Wiesel
on receptive fields got pretty close to the PCT view of perception.
Yes you are correct. I don't know if he lives, but should we invite him to
discuss how human beings control the perception of a yellow ball on a table
one and next time ten meters away? I think how he and we explain intensity,
sensing the color and the configuration and more.
bjorn
[from Gary Cziko 2007.07.05 05:55 CDT]
According to the Wikipedia <http://en.wikipedia.org/wiki/David_Hubel>, David Hubel is 81 years old.
His book Eye, Brain and Vision can be viewed online at <
http://hubel.med.harvard.edu/bcontex.htm>
–Gary
···
On 7/5/07, Bjørn Simonsen < bjornsi@broadpark.no> wrote:
[From Bjorn Simonsen (2007.07.05,08:55 EUST)]
From Rick Marken (
2007.07.04.2320)
I haven’t read it. But I think that Hubel’s work with Torsten Wiesel
on receptive fields got pretty close to the PCT view of perception.
Yes you are correct. I don’t know if he lives, but should we invite him to
discuss how human beings control the perception of a yellow ball on a table
one and next time ten meters away? I think how he and we explain intensity,
sensing the color and the configuration and more.
bjorn
–
Gary Cziko
Professor
Educational Psychology & English as an International Language
University of Illinois
1310 S. Sixth Street
210F Education Building
Champaign, IL 61820-6990
USA
Telephone +1-217-333-8527
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e-mail:
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[From Bjorn Simonsen (2007.07.05,15:05 EUST)]
from Gary Cziko 2007.07.05 05:55 CDT
According to the Wikipedia <http://en.wikipedia.org/wiki/David_Hubel>,
David Hubel is 81 years old.
His book Eye, Brain and Vision can be viewed online at <
http://hubel.med.harvard.edu/bcontex.htm>
Wonderful, I recommend that book, but I am not a neurobiologist.
Go to the chapter "A typical neural pathway" Look at graph nr. 2 (and nr. 3)
and read the text to the graph.
Read the text in the section that starts with "We also need to qualify our
model with respect to direction of information"
bjorn
[From Rick Marken (2007.07.05.0815)]
Bjorn Simonsen (2007.07.05,15:05 EUST)--
Gary Cziko 2007.07.05 05:55 CDT
>His book Eye, Brain and Vision can be viewed online at <
>http://hubel.med.harvard.edu/bcontex.htm>
Wonderful, I recommend that book, but I am not a neurobiologist.
Go to the chapter "A typical neural pathway" Look at graph nr. 2
(and nr. 3) and read the text to the graph. Read the text in the
section that starts with "We also need to qualify our
model with respect to direction of information"
I read that part and based on my reading I predict that Hubel would
not be a happy camper if he were invited to talk about control of
perception. He certainly allows that the "typical neural pathway" has
feedback loops within it but the diagram showing information starting
at receptors and ending at the muscle is the open loop, input output
model of behavioral organization all the way. My guess is that most of
what Hubel thinks of as internal neural feedback paths (carrying
information back in the direction of the receptors) are the paths of
reference signals.
Best
Rick
···
--
Richard S. Marken PhD
Lecturer in Psychology
UCLA
rsmarken@gmail.com