Brain Poke is just a simple simulation of Wilder Pennfield's
experiments on human subjects during neurosurgery. The experiments
were conducted in the 1950s and early 1960s and involved electrically
stimulating the cortex of subjects undergoing neurosurgical resections.
Most of these surgeries were performed to reduce the symptoms
of epilepsy. To the surprise of most people, these surgeries were
generally conducted with the patient awake. Many neurosurgical
procedures are still done this way. Being able to ask the patient
questions during surgery is often very important to the successful
outcome of the surgery. As for Pennfield's data, he simply believed
that the brain had a number of localized functions and this was
a way to map them out.
We are still in the mapping business today. Functional
neuroanatomical maps have been printed in texts since the 1700s
and we've gotten more sophisticated in making these maps. Newly
developed techniques such as the functional magnetic resonance
imaging (fMRI) give us an unparalleled view of the brain. It would
seem that we have only to do enough experiments to adequately
create a functional map, elaborating on the mapping which Pennfield
helped refine.
Unfortunately, while we have made marvelous technical
advances in watching brains, we have made almost no theoretical
advances in assigning function to structure. There are two problems.
The first is that we don't know the structure(s) of the brain.
This must seem a surprise and most readers must be reciting the
lobes and other names of brain structures. Still, we don't know
where to draw the boundaries in the geography of the brain as
it relates to function. Is it the dendritic trees of neurons which
are important? What about the number of cells in a cortical layer?
Should we make such decisions about similarities of brain regions
mini-column by mini-column? We just don't know.
The second difficulty is in determining function. Psychophysiologists
have been trying "officially" to determine the fundamental
elements of psychological process since the mid-nineteenth century.
Unofficial attempts go hundreds (maybe thousands) of years before
that. What are the fundamental elements of function? Seeing? Hearing?
Perhaps the dichotomy is between input and output? If that's true,
would planning for the future be input or output? These are very
difficult questions. Let's take an illustrative case: reading.
Reading is something you are doing now. But even within the confines
of what we know about function, it involves receiving an image
on the retina, focusing, moving the eyes, getting another image,
not getting sick because your eyes are moving, translating what
has been seen into a symbol system, and using the symbol system
to create knowledge about the world (or at least Brain Poke).
That's a lot of stuff and it's a very incomplete list. So, what
part of the brain does that? Many, many parts. What part of the
brain isn't working right in disorders like dyslexia? The answer
could be one of many, many parts.
So, while Brain Poke tries to be true to the original
experiments, don't be misled by the structure/function picture
that emerges. Assigning a psychological function like creativity,
language, emotion, or math ability to a spot in the brain or even
a whole hemisphere is just too simple to be real.
TL
11/18/97 |