A change in perception that explains the problem with a common kind of assumption:

Steven Michael Harris stevenharris at mediaone.net
Thu Nov 30 16:42:35 EST 2000


A change in perception that explains the problem with a common kind of
assumption:


In September or October I attended a lecture at MIT by a Harvard professor
(John Assad) where he presented his findings concerning studies of monkeys
that were taught to move a cursor from one point to another while the eye
was fixated on another target point on a computer screen. The researchers
discovered that some cells in a particular region of the brain would fire in
a particular way only when the cursor was being moved through the field of
view. Various controls were used along with prior knowledge of the fact that
that region of the brain is identified as a visual processing center to show
that the cells were responding to the perception of movement (rather than
reflecting the motor control needed to move the cursor).

In other related experiments the brain cells were monitored while the monkey
moved the cursor from point A to B in which the cursor would disappear while
it was still being moved to the goal. (The cursor would reappear when it got
very close to the target.) Some of the cells that were being monitored in
this experiment would fire in a particular characteristic way while the
cursor was moving on the screen and then these cells would lose that
particular pattern of firing during the period of time when the cursor
disappeared from the screen. Some cells were identified in this same visual
processing region that would fire in a characteristic way when the cursor
started moving from point to point and would continue firing in this way
even when the cursor disappeared on the screen.

These were wonderful experiments that provide a lot of information about the
workings of the brain. All of the observations (that I just summarized in a
simplistic way) were fact.

But a major mistake was made when the evaluation of these observations was
presented:

The conclusion was made that the cells that changed the pattern of firing
during the movement of the cursor through the visual field were cells that
registered (or calculated, or perceived) visual movement of this type. It
was taken for granted with these observations that these particular (and
relatively few) cells were doing the job of registering visual movement.

A similar conclusion was made about the cells that continued firing when the
cursor disappeared that these cells were probably calculating the imagined
visualization of movement of the cursor when the monkey struggled to get the
cursor to its target (and then get the reward of some fruit juice). This was
considered interesting evidence of cells that had the job of dealing with
mental visualization of movement (when the actual movement through the
visual field was removed).

These conclusions involve ways of speaking about the cells that go from the
facts of the experiment to theories about the nature of cells and the way
they work. The language used in these theories is wrong and this language
interferes with really understanding how the brain works.

Something as complex as the calculation of movement through the visual field
or the mental visualization of such movement can not be performed by such a
small number of cells. What the cells are doing is just firing on and off
(in a characteristic way related to such experiments, granted) and such
firings are the same as the firings of just about any cells in the brain,
even if the characteristics of such firings can be observed to be related in
time to particular events.

Millions of cells starting with the cells connected to the cones in the eye
are also involved with such calculations of movement in the visual field,
even if they don't ever fire in frequencies that correspond in time to the
existence of movement in the visual field. Cells that stop firing in
response to visual movement are also a part of such nerve cell decisions
that have an effect on the calculating of movement in the visual field (or
visualization of same). If millions of cells have a part in such information
(and they also have a small part in many other functions of "higher"
processing), they have relatively equal portions of such mental processing.

Just because these cells identified in the experiment are the only cells
observed in the brain to respond in time and in the character of their
firings to the existence of visual movement does not mean these are the only
cells involved in the processing of visual movement. Even if an experiment
that kills these particular cells results in a disability to register visual
movement (along with the inability to find other brain cells that, when
damaged, interfere with the same ability); it does not mean that these cells
alone are responsible for the perception of visual movement.

It could mean that such information and perception is intersecting in such a
small number of cells rather than that such processing is the job and
accomplishment of that small number of cells.

Let me explain:

Once again I'd like to use the example of a town phone network.

Consider the entire phone network as one function - the function of town
phone service. Every phone call, every phone conversation between all of the
people using the phone in that town have a portion of involvement in that
function of the existence of phone service and activity in that town. There
are operators and technicians and a wide variety of equipment that also
share a portion of the existence of phone service in that town. Imagine also
that there is duplication of a variety of switching equipment and of lines
that carry the phone signals around town.

In this phone system there is a particular small stretch of fiber-optic
cable that carries all of the phone signals in the town. At any time that
there is phone activity in the town - one phone call late at night or a
million calls simultaneously - there are signals being sent through this
particular cable. Because of the duplication of land lines and switching
equipment and the people involved, there is no other point in the town's
phone system where the presence of phone activity somewhere in town is
always involving that aspect of the system.

Each of the pieces of equipment involved, and the people involved when phone
service exists, have a portion of involvement in making phone service exist.

Observation of no phone in town or piece of switching equipment or
particular land line could be used to let you know if phone service exists
in that town. A line might be dead but phone service is still getting
through. A phone might not be in use but others in town are. etc.

The only point in the system where the existence of phone activity can
always be registered is in that fiber-optic cable. That cable is the only
part of the system that would totally disrupt service if it was broken. Does
that mean that the cable is the place where phone service is processed or
registered or calculated? No. That cable has an equal part of the puzzle
with every other part of the phone system, but that cable is where
everything intersects.

Each cell in the brain has a very, very small part of the processing of any
task. Cells that don't fire in a particular instant might be contributing
part of the processing too, by the fact of eliminating a line of reasoning -
an important decision. (The cell that is not firing is not participating in
the qualia, the perception, the consciousness, though.)

To visualize how this system works is very difficult. The first task is to
explain which ways of looking at it all are wrong.

To think of an individual cell or group of cells as having the ability to
perform some complicated function is to think of the cells as doing some
kind of unexplainable magic. This language also leads one to think of the
brain as a inflexible hardware that was created through extremely
complicated genetics organization. Actually all the cells do the same thing
and use the same language to make the system work. The way they communicate
creates the brain that evolves in an adult. The logic of the cells grows the
brain into that particular form and logic and geography because it is the
natural way the communication of the cells will create that form absent of
any traumas or factors that would corrupt this self-organization.

This problem with the concept of thinking that cells are accomplishing some
complicated task alone as a group in a particular region is another of those
fatal flaws of medical biological reasoning. Cells can participate as a
small part of many tasks and very great numbers of cells are required for
most higher functioning. Regions of the brain that have been identified as
the location of this function or that function are just the places where
those various functions are intersecting.

This concept gets in the way of many understandings. For instance: regions
of the brain have been wrongly recognized as the places where memories are
stored or organized but memory is something that occurs in almost every cell
and synapse of the brain. The reason this mistake has been made is because
there are some regions of the brain with many connections to the rest of the
brain that are the location of many higher order "intersections" of
processing. The memories are everywhere (in very small pieces of processing)
but the most important and obvious intersections of cognition are not
everywhere. (And, then again, every cell is an intersection of some piece of
cognition in another sense.)

This is very difficult to conceptualize and I will continue to write essays
that chip away at making sense of this to others.



(More related writing to be found at www.braintheory.net )








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