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Microelectrode Implants for Spinal Cord Stimulation in Rats


Nandra, Mandheerej Singh (2015) Microelectrode Implants for Spinal Cord Stimulation in Rats. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9930R3G.


Paralysis is a debilitating condition afflicting millions of people across the globe, and is particularly deleterious to quality of life when motor function of the legs is severely impaired or completely absent. Fortunately, spinal cord stimulation has shown great potential for improving motor function after spinal cord injury and other pathological conditions. Many animal studies have shown stimulation of the neural networks in the spinal cord can improve motor ability so dramatically that the animals can even stand and step after a complete spinal cord transaction.

This thesis presents work to successfully provide a chronically implantable device for rats that greatly enhances the ability to control the site of spinal cord stimulation. This is achieved through the use of a parylene-C based microelectrode array, which enables a density of stimulation sites unattainable with conventional wire electrodes. While many microelectrode devices have been proposed in the past, the spinal cord is a particularly challenging environment due to the bending and movement it undergoes in a live animal. The developed microelectrode array is the first to have been implanted in vivo while retaining functionality for over a month. In doing so, different neural pathways can be selectively activated to facilitate standing and stepping in spinalized rats using various electrode combinations, and important differences in responses are observed.

An engineering challenge for the usability of any high density electrode array is connecting the numerous electrodes to a stimulation source. This thesis develops several technologies to address this challenge, beginning with a fully passive implant that uses one wire per electrode to connect to an external stimulation source. The number of wires passing through the body and the skin proved to be a hazard for the health of the animal, so a multiplexed implant was devised in which active electronics reduce the number of wires. Finally, a fully wireless implant was developed. As these implants are tested in vivo, encapsulation is of critical importance to retain functionality in a chronic experiment, especially for the active implants, and it was achieved without the use of costly ceramic or metallic hermetic packaging. Active implants were built that retained functionality 8 weeks after implantation, and achieved stepping in spinalized rats after just 8-10 days, which is far sooner than wire-based electrical stimulation has achieved in prior work.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:spinal cord; spinal cord stimulation; spinalized rats; paralyzed rats; locomotion; locomotion recovery; functional electrical stimulation; stimulation; wireless power; implant packaging
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Electrical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Tai, Yu-Chong
Thesis Committee:
  • Tai, Yu-Chong (chair)
  • Edgerton, V. Reggie
  • Burdick, Joel Wakeman
  • Emami, Azita
  • Yang, Changhuei
Defense Date:14 September 2014
Funding AgencyGrant Number
National Institutes of Health - Bioengineering Research PartnershipsR01-EB0076151
Record Number:CaltechTHESIS:06052015-084726649
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8994
Deposited By: Mandheerej Nandra
Deposited On:05 Jun 2015 23:55
Last Modified:04 Oct 2019 00:08

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