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Optimally calibrated somatosensory neuroprosthesis for people with leg amputation and/or peripheral neuropathy
In neuropathies feet sensations might be lost due to nerve damage. This could be restored developing a neuroprosthesis that implements a non-invasive electrical stimulation at the ankle level. The modality and results of the many possible implementations must first be explored on healthy subjects.
Pressures foot sensations are important to keep a correct posture, maintain a physiological gait, and the pain sensations act as a protective measure against injuries. Neuropathies are damages to the nerves, that in some cases (e.g. Diabetes) are associated with a loss in foot sensations, consequently reducing substantially the quality of life of the subject, highly increasing the chance of falling and in worst cases amputation of the limb due to ulcers.
Our team has previously worked with amputees restoring the missing sensations using electrical stimulation, linking the intensity of an electrical stimulation to the force exerted underneath a prosthetic foot. The same approach could also be used in neuropathies, and a prototype to evoke sensations under the foot has already been developed and it’s ready to be tested. The concept is a novelty in the scientific research, and as such, no scientific literature has yet analyzed the characteristics of evoked sensations using non-invasive stimulation in lower-limb and intact limbs. The characterization should address the following important questions: 1. What is the best location to electrically stimulate inducing sensations under the foot? This should evaluate the degree of repeatability between different subjects (for the same placement), the association between electrodes and evoked locations, the possible variations during movement. 2. What is the best encoding to link pressure to stimulation? 3. What are the adaptation characteristics? 4. What are the best shapes for the electrodes? 5. What are the most common type of sensations evoked?
This will have to be done first on healthy subjects, as to have a “gold” starting point on correctly working fibers and be able to compare future results with neuropathy subjects.
Pressures foot sensations are important to keep a correct posture, maintain a physiological gait, and the pain sensations act as a protective measure against injuries. Neuropathies are damages to the nerves, that in some cases (e.g. Diabetes) are associated with a loss in foot sensations, consequently reducing substantially the quality of life of the subject, highly increasing the chance of falling and in worst cases amputation of the limb due to ulcers. Our team has previously worked with amputees restoring the missing sensations using electrical stimulation, linking the intensity of an electrical stimulation to the force exerted underneath a prosthetic foot. The same approach could also be used in neuropathies, and a prototype to evoke sensations under the foot has already been developed and it’s ready to be tested. The concept is a novelty in the scientific research, and as such, no scientific literature has yet analyzed the characteristics of evoked sensations using non-invasive stimulation in lower-limb and intact limbs. The characterization should address the following important questions: 1. What is the best location to electrically stimulate inducing sensations under the foot? This should evaluate the degree of repeatability between different subjects (for the same placement), the association between electrodes and evoked locations, the possible variations during movement. 2. What is the best encoding to link pressure to stimulation? 3. What are the adaptation characteristics? 4. What are the best shapes for the electrodes? 5. What are the most common type of sensations evoked? This will have to be done first on healthy subjects, as to have a “gold” starting point on correctly working fibers and be able to compare future results with neuropathy subjects.
The student will be guided in understanding the principal cause of neuropathy or lack of sensory feedback, its effects and meaning in terms of reduction of quality of life, the current state of the art of neuroprosthesis with scientific literature readings, and our developed sensory-feedback system.
The major goals (mandatory) for the student will be:
1. Design a set of sensory characterization to be made (e.g.: spread and evoked locations depending on the intensity of injected charge).
2. Investigations about the electrodes placements
3. Investigations about the electrodes shapes and their efficacy
4. Investigations about different stimulation strategies (e.g.: non-linear increase of intensity, short duration with high intensity, high duration with short intensity …)
5. Test on volunteers to obtain a statistical meaningful description of cause-effect
The student will be guided in understanding the principal cause of neuropathy or lack of sensory feedback, its effects and meaning in terms of reduction of quality of life, the current state of the art of neuroprosthesis with scientific literature readings, and our developed sensory-feedback system. The major goals (mandatory) for the student will be: 1. Design a set of sensory characterization to be made (e.g.: spread and evoked locations depending on the intensity of injected charge). 2. Investigations about the electrodes placements 3. Investigations about the electrodes shapes and their efficacy 4. Investigations about different stimulation strategies (e.g.: non-linear increase of intensity, short duration with high intensity, high duration with short intensity …) 5. Test on volunteers to obtain a statistical meaningful description of cause-effect
Dr. Stanisa Raspopovic, Assistant Professor Neuroengineering laboratory, Head ETH Zurich, Switzerland Email: stanisa.raspopovic@hest.ethz.ch
Dr. Giacomo Valle, Postdoc at Neuroengineering laboratory, Email: giacomo.valle@hest.ethz.ch
Dr. Stanisa Raspopovic, Assistant Professor Neuroengineering laboratory, Head ETH Zurich, Switzerland Email: stanisa.raspopovic@hest.ethz.ch Dr. Giacomo Valle, Postdoc at Neuroengineering laboratory, Email: giacomo.valle@hest.ethz.ch