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Recording from dorsal roots - problems...

Danny Banks D.Banks at ee.surrey.ac.uk
Wed Nov 3 17:41:58 EST 1993


I'm trying to write up my thesis, and would like to generate a little
discussion to help me with it. I'm not aware of anyone at the University here
who can help....

I am trying to make a good case for using an array of highly selective 
electrodes for recording sensory signals from the spinal nerves; primarily
the dorsal roots. This being preferable to using less selective electrodes
implanted much more distally to the spinal cord to record from nerve
branches innervating specific areas of the body. The eventual application
would be in sensory feedback for FES in cases of spinal cord injury.

My present arguements are based on comments by Loeb et. al. (1980), as well as
other stuff I've read.


- By implanting at the dorsal roots, you reduce the number of devices that you
  have to implant to get the same information.

- The signals recorded are uncomplicated by motor signals, and stimulation
  artefacts (if the stimulating electrodes are implanted at the ventral roots).

- Being close to the spinal column, the devices are more mechanically isolated,
  and interconnection problems are eased.

I intend to show in my thesis that the problem of recording single unit signals
that are only stable for a few days at best, can be overcome without using
exceedingly complicated signal processing software or hardware.

My main concern at the moment relates to the problems of implanting so close to
the spinal cord. It may be preferable to implant a large number of devices more
distally, than a few devices in the dorsal roots of the spinal nerves - because
there may be risks of causing additional damage, and surgical problems when
trying to implant at the spinal roots. This may be of particular concern when
there is only partial damage to the spinal cord.

I would very much appreciate comments on this.

I've directed follow-ups to bionet.neuroscience (hope news is working here
today :)

Thanks a lot.



GE Loeb, B Walmsley, J Duysens. (1980). "Obtaining Proprioceptive Information
from Natural Limbs: Implantable Transducers vs. Somatosensory Neuron
Recordings". Chapter 10 in: _Physical Sensors for Biomedical Applications_,
MR Neuman et. al. (eds.), CRC Press, Boca Raton Fl. p 135-149.

Danny Banks.				 		 eep1db at ee.surrey.ac.uk
I'm *not* a mad scientist............................I'm an eccentric engineer.

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