Processing capability of the spinal cord

Walter Eric Johnson wej3715 at fox.tamu.edu
Sun Dec 6 04:19:32 EST 1998


I read about Susan Harkema's work in rehabilitating patients
with complete SCIs.  For those not familiar with this, she
provided appropriate sensory input to her SCI patients on
a treadmill while a trainer helped the patient perform
stepping motions by extending the leg, placing the foot on
the treadmill, picking up the foot, ... .  After several
months of therapy, all seven patients developed rudimentary
walking skills including the ability to support some of their
own weight.  They were able to step as they were taught by
the trainer in spite of the fact that they had no conscious
perception of joint positioning.  They also did not develop
much balance, if any.

It is normal for some level of reflex actions to return
after a short period of time following a spinal column
injury.  But this doesn't appear to be related to the
reflexes (at least to me).

The obvious question is how extensive are the processing
capabilities of the spinal cord?  According to a book I
read last Christmas (the chapters on neuroscience anyway)
the spinal cord provides a very large portion of the processing
required by many insects.  I asked a recent PhD in neuroscience
about this and he claimed it was nonsense.  Since then, I've
often wondered how extensive are the processing capabilities
of the spinal cord.  I haven't seem much mention of this in
any books (other then discussions relating to reflexes) but
I haven't performed any systematic searches for this information,
either.  (I'll have to correct that error in the near future.)

Also, what other bodily processes might also benefit from
this?  For example, does it seem possible that SCI patients
might be able to develop some bladder control by such
techniques or does the lack of a connection to the pontine
micturition center remove that from any such possibility?
Would the presence of micturition related reflexes be a
good indication that with proper training, this might be
possible?

How about injuries near the C3 level?  Is it possible that
this technique might be able to restore some ability to
breathe without support?  (Obviously, they would not want
to depend on this ability but it might be nice in an
emergency.)

I also have some questions about Dr. Harkema's results, too.
In particular, when someone is "walking" on the treadmill,
what happens when the treadmill stops?  Does the stepping
motion continue?  Or does the spinal cord receive information
that a foot has stopped and break the sequence of nerve
impulses?

Eric Johnson



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