Finger coordination

CSGnet Archive CSG2004
1

[From Bjorn Simonsen (2004.11.23,12:10 EST)]

(I think many loops are involved in the text below, but I express myself I
an aggregated way)
The way I understand some of the three lowest levels of HPCT is described in
figure 9.1 in chapter 9 in BCP (a nice figure). When I move my forearm up
and down, knocking in the table as fast as I can there is coming a reference
to the Event level. I can do it about 340 times/minute.
If I move my forefinger up and down, knocking in the table as fast as I can,
I can do it about 310 times/minute.

When I do the test I measure the time knocking 50 times.

On the way to the fourth level the axons meet other neurons in synapses
where transmitters cause electrical impulses in the dendrites of the next
neuron. The impulses moves very quick in the neurons and the synaptic
transmission represent a delay.

Here is my problem. I study some neurological literature and find that the
neuron impulses that control the finger movement don't follow the same
channels as the impulses controlling the biceps e.g.. From the motor center
in the cortex they go direct to the fingers. They don't pass synapses in the
brain stem and in the spine cord.

If this is correct I think I could have done more finger knocks than
forehand knocks. Do the experiment tell me that the neurons to and from the
fingers also pass synapses in the brain stem and in the spinal cord?

Any thoughts?

Bjorn

2

[From Bill Powers (2004.11.23.0710 MST)]

Bjorn Simonsen (2004.11.23,12:10 EST) --

Here is my problem. I study some neurological literature and find that the
neuron impulses that control the finger movement don't follow the same
channels as the impulses controlling the biceps e.g.. From the motor center
in the cortex they go direct to the fingers. They don't pass synapses in the
brain stem and in the spine cord.

There are several. answers to your problem. First, see B:CP p. 113, in the
section titled "the second order of organization." The area of the cerebral
cortex around the central sulcus appears to be a set of second-order
systems, despite their location. Counting synapses seems to support that
idea. The geometric arrangements in the brain do not necessarily reflect
the functional organization. Some parts of the cortex are at the same
functional level as parts of the brainstem and midbrain. They may be later
additions, but they are not of higher order. I didn't mention it, but some
higher-order systems may actually exist in the brain-stem or spinal cord.
Decerebrated dogs can still execute the alternating changes in leg position
that accomplish walking.

The second answer is that second-order control systems do not control rates
of occurrance of events. They are used by event-control systems, but the
variables they control are not rates of repetition. The speeds of
repetition you are observing reflect the speed of perception and action of
a fifth-order system, I think, though I am far from satisfied with my
definition of that level. Fifth-order systems operate by sending reference
signals to fourth-order (motion, rate-of-change) systems, which operate by
sending reference signals to third-order (configuration, position) control
systems, which operate by sending reference signals to sensation (effort)
control systems, which operate the first-order (force) control systems.

That, I add, is the theory as it stands now, whether correct or not.

Best,

Bill P.

3

[From Rick Marken (2004.11.23.1440)]

Bjorn Simonsen (2004.11.23,12:10 EST)--

The way I understand some of the three lowest levels of HPCT is described in
figure 9.1 in chapter 9 in BCP (a nice figure). When I move my forearm up
and down, knocking in the table as fast as I can there is coming a reference
to the Event level. I can do it about 340 times/minute. If I move my
forefinger up and down, knocking in the table as fast as I can, I can
do it about 310 times/minute.

Good work! It's nice to see real data. But your results are somewhat
different from what I get. When I tap by moving my forearm and when I tap
just with my forefinger I do about 7 taps/second. According to your data you
are tapping with the forearm at about 5.6 taps/sec and with the forefinger
about 5.1 taps/sec. Maybe you're going more slowly than I am in order to be
able to count. I just count to twenty taps and try to get the time measure
on that. When I go over 20, keeping track of the count gets tough for me.

Here is my problem. I study some neurological literature and find that
the neuron impulses that control the finger movement don't follow the
same channels as the impulses controlling the biceps e.g.. From the
motor center in the cortex they go direct to the fingers. They don't
pass synapses in the brain stem and in the spine cord.

If this is correct I think I could have done more finger knocks than
forehand knocks. Do the experiment tell me that the neurons to and
from the fingers also pass synapses in the brain stem and in the
spinal cord?

Any thoughts?

One thought is about the data itself. Are you sure there is really a
difference in the rate at which you can tap using forearm vs forefinger? I
get no reliable difference at all, but perhaps I'm not doing what you are
doing.

Second, if there is a reliable difference in the rate at which you can do
the tapping, this does not necessarily mean that tapping with the forearm vs
forefinger are at different levels of control. The level of control in PCT
is defined on the input side, not the output side.

When you tap repetitively you are controlling a perception of a rate --
either of pressure changes at the finger tip or of sounds in the ear. I
think of this as a transition perception. The level of the perception being
controlled determines the maximum rate at which you can perceive and thus
control the perception. See my "Hierarchical behavior of perception" paper
in _More Mind Readings_ for a better description of this thesis, which is
that the speed at which you can perceive and, thus, control a variable is a
reasonable indication of the level of the perception in the perceptual
hierarchy.

If there is a real speed difference when tapping with the forearm vs the
forefinger, it may result from differences in mechanical rather than neural
architecture that is limiting the speed. The same perception (rate of
tapping) is being affected when using the forearm or forefinger so the
faster speed is probably closest to the maximum speed at which the
controlled perception can still be perceived --ie. The speed that "defines"
the level of control as per the "Hierarchical behavior..." chapter.

Also try the "Hierarchy of perception and control" demo at:

http://www.mindreadings.com/ControlDemo/HP.html

This demo also illustrates the thesis that speed can be used to find
relative level of control of a perception. In that demo, the same "output"
system (finger press) is used to control all three perceptions so the
difference in speed of control is clearly limited by the input and not the
output side of the loop.

Best regards

Rick

ยทยทยท

--
Richard S. Marken
MindReadings.com
Home: 310 474 0313
Cell: 310 729 1400

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4

[From Bjorn Simonsen (2004.11.24,11:15 EST)]

From Bill Powers (2004.11.23.0710 MST)

The geometric arrangements in the brain do not necessarily reflect
the functional organization. Some parts of the cortex are at the same
functional level as parts of the brainstem and midbrain. They may be later
additions, but they are not of higher order.

I think it is rational to think evolution. What parts of brain do we find
more of in human organisms than in chimpanzees and fishes? What can human
organisms do that other animals can't do?

I didn't mention it, but some
higher-order systems may actually exist in the brain-stem or spinal cord.
Decerebrated dogs can still execute the alternating changes in leg position
that accomplish walking.

This is new for me, but I can't imagine they are at the fifth level?

The second answer is that second-order control systems do not control rates
of occurrance of events. They are used by event-control systems, but the
variables they control are not rates of repetition.

Maybe I expressed myself not clear, but this is also how I think.

The speeds of repetition you are observing reflect the speed of perception
and action of a fifth-order system, I think, though I am far from satisfied
with my definition of that level.

I guess you are right, but I thought knocking the table as quick as I can
with my forefinger is a fourth level control system. I know the fourth level
gets a reference from above, but I can't put it into words what kind of
fifth level (or is it the program level?) the reference should come from.

Fifth-order systems operate by sending
reference signals to fourth-order (motion, rate-of-change) systems, which
operate by sending reference signals to third-order (configuration,

position)

control systems, which operate by sending reference signals to sensation

(effort)

control systems, which operate the first-order (force) control systems.

This is also how I think.

bjorn