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Towards vestibular implants: effective pulse modulation in human patients and electrically evoked compound action potentials in animal models

Author(s):

K. Nguyen
Conference/Journal:

Co-supervised by Prof. Silvestro Micera. Co-referee Dr Barry Seemungal
Abstract:

We use our five senses in everyday life to interact with our environment. A sixth sense – the sense of balance – helps us navigate and orient and the vestibular system is the main contributor to this sense. Its sensory organs are located in the inner ear. Bilateral loss of vestibular sensation (BVL) is severely debilitating and significantly reduces quality of life. Affected patients have currently no effective treatment option and a vestibular implant (VI) might be the most promising option. The field of vestibular implant research is entering an exciting period. More than a decade of animal work is now being translated to human patients and studies with patients are surging forward. With several collaborators within the EU-US project CLONS, we made further inroads towards a commercial VI. In the first part of this thesis, we developed a real-time research platform to investigate pulse rate and pulse amplitude modulation. These two modulation paradigms were then tested in four BVL patients which were instrumented with modified cochlear implants for vestibular stimulation. Our results strongly support pulse amplitude modulation as stimulation paradigm for implant activation because it evoked significantly stronger eye movement responses. Furthermore, a model of the eye movement reflex pathway provided insights into how differently the two modulation paradigms engage vestibular afferents. Future experiments should investigate how the performance of these modulation paradigms changes with continuous stimulation as animal research suggests improvements in eye movement response over time. In the second part of the thesis, we lay the groundwork to pursue the goal of a closed-loop VI that could boost implant performance. We adapted artifact reduction techniques to record vestibular electrically evoked compound action potentials with a custom electrode array. We then correlated these compound potentials to eye movement responses for different stimulation scenarios that would resemble the operating mode of a VI. Our results showed a piecewise, linear pattern that could be used clinically for implant fitting (i. e. identification of stimulation thresholds). Our results also showed that utilization of these compound potentials as feedback signal in a closed-loop VI may be feasible and requires further work.

Year:

2015
Type of Publication:

(03)Ph.D. Thesis
Supervisor:

M. Morari

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% Autogenerated BibTeX entry
@PhDThesis { Xxx:2015:IFA_5357,
    author={K. Nguyen},
    title={{Towards vestibular implants: effective pulse modulation in
	  human patients and electrically evoked compound action
	  potentials in animal models}},
    school={},
    year={2015},
    address={},
    month=feb,
    url={http://control.ee.ethz.ch/index.cgi?page=publications;action=details;id=5357}
}
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