The central goal of this project is to advance the therapeutic applications and the development of an exciting novel neuroprosthetic technology, Safe Direct Current Stimulation (SDCS). Direct current (DC) compared to biphasic charge balanced pulses normally used by neural prostheses to interface to the nervous system, can more naturally control neural activity. Unlike biphasic current pulses used to excite neurons, DC can excite, inhibit, and modulate sensitivity of neurons. However using DC for implantable prosthetic applications has not been possible due to the DC's inherent violation of the charge injection safety constraints at the metal electrode interfaces. Safe DC overcomes these constraints and opens a new avenue for research into exciting possibilities of using DC to interface to the nervous system. We will optimize the use of safe DC to improve the performance of a vestibular prosthesis for those suffering from balance disorders. Vestibular prostheses encounter difficulty encoding head motion away from the implanted vestibular labyrinth because encoding this motion requires inhibition of spontaneous activity of the nerve. We obtained preliminary data in a chinchilla animal model showing that modulating the amplitude and polarity of safe DC could encode both ipsilateral and contralateral head rotations. Here we propose to understand and overcome the hurdles that we encountered in our preliminary experiments stemming from the key safe DC stimulation challenge: the reversal of neural response as a function of increased safe DC intensity. That is, anodic (positive) stimulation causes inhibition at low DC intensities but excitation at higher intensities; and cathodic (negative) stimulation causes excitation at low DC intensities but inhibition as the amplitude increases. In the vestibular prosthetic stimulation this effect imposes a limit on the velocity of encoding head motion. We also propose to advance the SDCS technology by identifying and solving the key technical challenges with a miniaturized SDCS to improve longevity and power consumption.
Aim 1) Improve the vestibular prosthetic encoding of head motion. We will investigate the origin of the response reversal and improve the head velocity encoding by eliminating or reducing the reversal with a bipolar stimulation paradigm.
Aim 2) Examine the safety of SDCS. We will examine the physiological and histological limits of safe DC stimulation in chinchillas stimulated for 60 days.
Aim 3) Address key technical challenges associated with longevity and low power consumption of the miniaturized SDCS.

Public Health Relevance

Neural prostheses are able to deliver reliable and efficient functional excitation of the nervous system to enable technology such as cochlear implants, retinal implants, pacemakers, spinal cord stimulators, and deep brain stimulators. Conversely, suppression of the nervous system is not easily achieved. The central goal of this project is to advance the technology toward achieving safe and efficient suppression of the nervous system and to improve the application of neural prostheses for the treatment of balance disorders.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS092726-05
Application #
9765416
Study Section
Bioengineering of Neuroscience, Vision and Low Vision Technologies Study Section (BNVT)
Program Officer
Kukke, Sahana Nalini
Project Start
2015-09-01
Project End
2020-08-31
Budget Start
2019-09-01
Budget End
2020-08-31
Support Year
5
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Johns Hopkins University
Department
Otolaryngology
Type
Schools of Medicine
DUNS #
001910777
City
Baltimore
State
MD
Country
United States
Zip Code
21205
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Cheng, Chaojun; Nair, Ankitha Rajagopalan; Thakur, Raviraj et al. (2018) Normally closed plunger-membrane microvalve self-actuated electrically using a shape memory alloy wire. Microfluid Nanofluidics 22:
Cheng, Chaojun; Thakur, Raviraj; Nair, Ankitha Rajagopalan et al. (2017) Miniature Elastomeric Valve Design for Safe Direct Current Stimulator. IEEE Biomed Circuits Syst Conf 2017:1-4
Fridman, Gene (2017) Safe Direct Current Stimulator design for reduced power consumption and increased reliability. Conf Proc IEEE Eng Med Biol Soc 2017:1082-1085
Ou, Patrick; Fridman, Gene (2017) Electronics for a Safe Direct Current Stimulator. IEEE Biomed Circuits Syst Conf 2017: