[From Bjorn Simonsen (2004.07.09.13:05
EuST)]
[From Rick Marken
(2004.07.07.0845)]
I
am putting it up on the web in order to solicit suggestions,
requests
for clarifications and so on.
Bimanual control is interesting. May I talk
a little around?
It is customary to say that our left
cerebral hemisphere send output signals to our right extremities. I don’t know
what PCT/HPCT say about that. Have you talked about that earlier?
As I understand (and here I might be wrong)
the first level outputs come from the cerebral cortex. There are two cerebral
cortexes, one in each cerebral hemisphere. Signals from first level can pass to
the second level that we also find different places in the cerebral hemispheres.
I remember from B:CP Bill’s account
about Hess’s experiments. These experiments tell us that third level is in the
thalamus region. There is just one thalamus, therefore perceptual signals from
both cerebral hemispheres go to thalamus or further. All higher levels are
represented in one region, not as the motor cortex (two hemispheres).
Your model is a control system at the
sixth level (the logical one)??. The
output goes down to the third level and there are probably many references that
distributes to the two hemispheres and motor outputs goes to the right arm from
the left hemisphere and opposite. (You have a more simple model).
If they really control da/dt, I guess
the reference value to the first level systems would be the same value. But
most people have their best arm and I guess there are different gains and
slowing factors in the two systems. Because
of the feedback the two perceptual signals in the two systems become different.
Then we get a conflict??? Can this explain why people producing antiphase rotations would often end up
controlling for symmetry as they increased the speed of flag rotation?
I have tried some experiments myself. I
have placed two ordinary dinner plates on the table and moved my clenched fists
round and over the plates circumferences. It works very well when I do it
symmetric. If I do it 180 degrees asymmetric, I gradually continue with
symmetric movements.
When I move my arms symmetric I use the
same muscles at the same time, when I move my arms asymmetric I more or less
use “opposite” muscles at the same time. May also this be a reason why people producing antiphase rotations would often end up
controlling for symmetry as they increased the speed of flag rotation?
Over
to your Mechsner model.
On your web you have written, “While there was a 1:1 relationship between left hand
rotation and left flag rotation, there was only a .75:1 relationship between
right hand rotation and right flag rotation.”
I
prefer ““While there was a
1:1 relationship between left hand rotation and left flag rotation, there was
only a 1:1.33 relationship between right hand rotation and right flag
rotation.” Remember it is just what I prefer.
Your
figure 2 is indistinct on my Explorer. I had to copy it to a Paint program
where I can zoom it.
In
your figure 2 I see your model has two levels. That is nice, but you should
present a short account about PCT/HPCT (the first levels). You asked for our/my
views. You have a nice presentation |”The Hierarchical Behavior of Perception”.
Why not have a reference to that essay,
You
have a figure 3 that explain the diagram we get after running the simulation.
But I would have used some words describing the table. I would not used decimal
numerals telling each turn of the flag (z) and I would have more numbers on the y-axis. I would also
explained that your statistic is taken each 0.1 second (??) and telling that
the z-axis describes how many percent of the counting you get a certain angular-difference
value. I say this because I used much time to understand the z-axis. But that
is me.
This
was interesting. Maybe we can talk more about bimanual coordination after
Chicago. It tells much about the brain
Have
a nice conference in Chicago. If I had been there I would also visited The North
Western University. I know they do it well with Nano technology, with organic
molecules as transistors, molecules that can multiply themselves. They should
know about PCT.
bjorn