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Acquisition and Analysis of Vestibular Evoked Potentials in the Horizontal Semicircular Canal of an Animal Model

Author(s):

Vinzenz Kögler
Conference/Journal:

Master Thesis, FS 10 (10046)
Abstract:

Sight, hearing, touch, smell and taste – asking a random person to name all human senses those are the ones the person will most likely respond with. Yet another sense of which people may not consciously consider is the sense of balance. It is incorporated in a pair of organs, one each located in the inner ear on both sides of the head. Due to its complex anatomy it is called the vestibular labyrinth. In a highly fascinating yet simple fashion it perceives every movement of our head. It helps us focusing our vision on specific points in space, as we are actively moving or passively being moved through our environment. In combination with the other sensory inputs it is integrated to help us for example maintain control of our body posture. A key output of the vestibular system is the vestibulo-ocular reflex (VOR). The VOR is a response to motion of the head by the vestibular system that elicits an eye movement that compensates for the head motion, stabilizing our gaze. Without this reflex we would constantly suffer from a blurred vision (i.e. oscillopsia). A dysfunctional vestibular system can be debilitating, e.g. it can lead to severe cases of vertigo, perceiving a rotation as if spinning wildly around a carousel without actually moving at all. Similar to the auditory nerve where a hearing sensation can be elicited electrically or muscles where electrical stimulation can force a muscle contraction, it is possible to electrically stimulate the vestibular nerves in order to provide a motion sensation. We define the activity of the vestibular nerves in response to an electrical stimulation as Vestibular Evoked Potential (VEP). Generally this method is referred to as functional electrical stimulation (FES) and is already used in a wide range of medical treatments, e.g. deep brain stimulation for Parkinson’s disease treatment, cochlear and retinal implants, spinal cord rehabilitation or physiotherapy for muscular impairments. To provide people that suffer from vestibular disorders with a medical treatment or even a permanent solution, the CLONS project (Closed Loop Neural Prosthesis for Vestibular Disorders) aims for the development of a neural prosthetic based on the specific application of electrical stimulation to vestibular nerves. This thesis contributes to the CLONS project by conducting basic research on electrically evoked vestibular potentials. Researchers are already investigating electrophysiological recordings of vestibular evoked myogenic potentials (VEMP) (Eleftheriadou & Koudounarakis, 2010). Those recordings are acquired with peripheral electrodes, making use of a vestibular reflex where a specific acoustic signal causes a contraction of the sternocleidomastoid muscle. So far, research on vestibular stimulation effects has focused on vestibular responses on the level of the VEMP or VOR. When analyzing VEMP and VOR, you measure a signal that has already been passed through a cascade of synapses – confronting us with a black box of signal processing that is between the location of stimulation and the site of our measurement. The goal of this thesis is to record electrically triggered VEPs inside of vestibular structures of a guinea pig and to identify the correlation between characteristic properties of the VEP (e.g. delay, amplitude, duration) and the parameters of the stimulation. It is the first one to look at the effects of electrical stimulation on the VEP and to record from inside the vestibular structures, therefore being significantly closer to the center of nervous excitation. Succeeding with this task would open the door to characterizations of neural potentials from the first stage onwards. By providing a principled recording and analysis method for VEP, we hope to revolutionize stimulation methods for vestibular implants and slingshot it closer towards clinical implementations. This unprecedented tool for vestibular research will certainly help us to learn more about not only stimulation efficiency, but also about the electrophysiology of vestibular neurons such as nervous excitation, signal transduction in neuronal networks, adaptation and many more. Eventually this research will enable us to create a vestibular implant that not simply responds to head motion, but which stimulates vestibular nerves and simultaneously monitors VEPs, dynamically reacts to changes in the physiology and automatically adjusts stimulation parameters – closed-loop control.

Year:

2011
Type of Publication:

(12)Diploma/Master Thesis
Supervisor:

S. Micera

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% Autogenerated BibTeX entry
@PhdThesis { Xxx:2011:IFA_3755
}
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