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<div class="block title"><h1>I. Extra-neural electrodes</h1></div> | <div class="block title"><h1>I. Extra-neural electrodes</h1></div> | ||
− | <div class="block title"><h3 style="text-align: left;"></h3></div> | + | <div class="block title"><h3 style="text-align: left;">1. Helicoidal electrode interface:</h3></div> |
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− | <p></p> | + | <p>Helicoidal electrodes are placed surrounding the nerve and are made of flexible metal ribbon in a helical design. This design allows the electrode to conform to the size and shape of the nerve to minimize mechanical trauma. The structural design causes low selectivity. Helicoidal electrodes are currently used for functional electrical stimulation, to control intractable epilepsy, sleep apnea, and to treat depressive syndromes.</p> |
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− | <div class="block title"><h3 style="text-align: left;"></h3></div> | + | <div class="block title"><h3 style="text-align: left;">2. Cuff electrode:</h3></div> |
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− | <p></p> | + | <p>Considered as extraneural electrodes, cuff electrodes are widely used to perform basic and applied electro-neurophysiology studies and are particularly interesting for their ability to achieve good nerve recruitment with low thresholds. The cuff-style electrode provides a cylindrical electrode contact with a nerve for each of an arbitrary number of contacts, is easy to place and remove in an acute nerve preparation, and is designed to fit on the nerve (Cf. Figure 1). For each electrode, the electrical contacts were cut from metal foil as an array so as to maintain their positions relative to each other within the cuff. Lead wires were soldered to each intended contact. The structure was then molded in silicone elastomer, and individual contacts were electrically isolated. The final electrode is curved into a cylindrical shape with an inner diameter corresponding to that of the intended target nerve. These electrodes have been successfully used for nerve stimulation, recording, and conduction block in a number of different acute animal experiments by several investigators.</p> |
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+ | <div class="legend"><b>Figure 1: </b>Schematic of a nerve cuff electrode. Retrieved on Oct. 14th from MicroProbes for Life Science<sup>[1]</sup></div> | ||
+ | <p>The activity recorded by the cuff electrode represents the simultaneous activity of a large number of active axons. The potential of action seen by the electrode are overlapped, allowing only a "global" image of the activity inside the nerve. As a result, the selectivity of the recording is limited by the number of axons undergoing simultaneous discharge and by the position and surface of the contact of the cuff electrode. This type of measurement therefore does not allow the identification of fiber activity alone.</p> | ||
+ | <p>Increasing the number of electrode poles allows to increase the selectivity of this type of electrode. A multi-pole cuff electrode is then called a cuff electrode having more than three contacts. These contacts can be rings or segments of rings.</p> | ||
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− | <div class="block title"><h3 style="text-align: left;"></h3></div> | + | <div class="block title"><h3 style="text-align: left;">3. FINE electrode:</h3></div> |
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− | <p></p> | + | <p>The flat-interface nerve electrode (FINE) was designed for selective nerve recording by realigning the fascicles and reshaping the nerve into a more flattened cross section which increases the surface area of the exposed nerve and offers greater access to fascicles. This kind of electrode is particularly interesting as it was possible to achieve more than 90% selectivity (Cf. Figure 2)</p> |
+ | <img src=""> | ||
+ | <div class="legend"><b>Figure 2: </b>Cross section and schematic of a FINE electrode<sup>[2]</sup></div> | ||
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<div class="block title"><h1>II. Information extraction: </h1></div> | <div class="block title"><h1>II. Information extraction: </h1></div> | ||
− | <div class="block title"><h3 style="text-align: left;"></h3></div> | + | <div class="block title"><h3 style="text-align: left;">1. Extraction of the discharge frequency:</h3></div> |
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− | <p></p> | + | <p>The most relevant information to extract is the discharge frequency of active fibers because it represents the means of coding information by the nervous system. Significantly, such processing must be applied to signals representing the activity of a limited number of fibers. In fact, the published examples relate exclusively to intra-neural collection: the only method, today, which allows to observe the activity of fibers alone. However, since we don’t want to use intra-neural electrode in our device we will not detail how to extract the discharge frequency.</p> |
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− | <div class="block title"><h3 style="text-align: left;"></h3></div> | + | <div class="block title"><h3 style="text-align: left;">2. Envelope extraction:</h3></div> |
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− | <p></p> | + | <p>Rectification and Bin-Integration (RBI) of the nerve raw signal is widely used in rehabilitation application. This point of RBI ENG are found by calculating the average of the absolute value of ENG samples spread over a given period of time. This period is called “bin” and its value depends on the application. It ranges from 10 ms to 200 ms. The smoothed envelope-like signal created by RBI makes it easy to extract information about the innervated organ.</p> |
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− | <div class="block title"><h1>III. Improvement of the electroneurogram records selectivity | + | <div class="block title"><h1>III. Improvement of the electroneurogram records selectivity</h1></div> |
− | <div class="block title"><h3 style="text-align: left;"></h3></div> | + | <div class="block title"><h3 style="text-align: left;">1. ENG-EMG selectivity:</h3></div> |
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− | <div class="block title"><h3 style="text-align: left;"></h3></div> | + | <div class="block title"><h3 style="text-align: left;">2. Type of nerve fiber selectivity:</h3></div> |
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− | <div class="block title"><h3 style="text-align: left;"></h3></div> | + | <div class="block title"><h3 style="text-align: left;">3. Spatial selectivity:</h3></div> |
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− | <div class="block title"><h1>IV. An example of the development of a multi-channel acquisition device | + | <div class="block title"><h1>IV. An example of the development of a multi-channel acquisition device</h1></div> |
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+ | <div class="block title"><h1>References</h1></div> | ||
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+ | <ul style="text-align: left;"> | ||
+ | <li></li> | ||
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Revision as of 12:02, 15 October 2018
MEMBRANE
When manipulating genetically engineered organisms, it is crucial to guarantee the confinement of these organisms. In our case, we want the genetically modified bacteria to stay at the interface between the prosthesis and the external organic medium. At the same time, one of the main issues our project wants to tackle is the conduction of the neuron influx to the prosthesis. The answer to these questions came as a double solution: confinement of the bacteria by conductive nanoporous membranes. The membrane’s nanoporosity allows substances produced by our modified biofilm to pass through the membrane, but the bacteria remain confined. We tested the conductivity and biocompatibility of two types of membranes.
Membrane
Nerve modelisation
As seen in the other parts of this wiki, we chose to use an nanoporous membrane in our device. The first goal of the membrane was to confine our biofilm, so it does not escape the prosthesis. Moreover, we also used our membrane as a conductive electrode. This solution was interesting since we didn’t have enough time to develop an entire electrical device which collect and treat the signal of the nerves. However, we know we still need to improve our interface if we want the patient to fully control his prosthesis. That is why we decided to look at what is already made in this field. So, first, we detailed how it is possible to model the electrical characteristics of a nerve. Then, we searched information on electrodes and signal treatment.