Patent Publication Number: US-10779730-B2

Title: High-contact density electrode and fabrication technique for an implantable cuff design

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/529514, filed Jun. 21, 2012, which claims the benefit of U.S. Provisional Application No. 61/571,129, filed Jun. 21, 2011, each of which is incorporated in its entirety herein by reference. 
    
    
     GOVERNMENT LICENSE RIGHTS 
     This invention was made with government support under Grant No. 2R01-Ns 032845-10 awarded by the National Institute of Health. The government has certain rights in the invention. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This application relates generally to a method and apparatus for monitoring electrical signals conducted by a nerve and, more specifically, to an in-vivo nerve interface comprising an electrode array, a method of utilizing signals sensed by the electrode array to control a prosthetic device, and a method of fabricating the electrode array. 
     2. Description of Related Art 
     Despite great advances in many areas of medical technology, the challenge of providing amputees with a prosthetic limb having the intuitive control and functionality of a natural limb remains. Improvements in materials have made prosthetics lighter and stronger, but little headway has been made in improving the functionality and control over the prosthetics by amputees. In an effort to improve the functionality and control of prosthetics attempts have been made to utilize electrical control signals from the muscles of the residual limb. While such techniques may hold future promise they have, thus far, not proven to be sufficiently robust and lack the use of intuitive control signals that would allow the amputee to take advantage of a dexterous prosthetic. 
     A more-recent goal in designing prosthetics is to give amputees more functionality, ideally approaching the level of functionality afforded by the limbs the prosthetics are to replace. Enabling an amputee to effectively utilize and control a prosthetic limb with so many degrees of freedom requires the prosthetic to respond to the numerous control signals used by the human body that would otherwise control the limb replaced by the prosthetic. Interfacing with the amputee&#39;s nervous system provides the opportunity to sense movement intention directly, affording the amputee natural, volitional control of the prosthetic. Attempts at decoding the amputees&#39; intentions in controlling a prosthetic directly from the brain have involved the use of electroencephalograms recorded from the surface of the scalp, and penetrating cortical arrays. But since so many bodily control signals are transmitted by the brain it is difficult to isolate the signals intended to control a prosthetic from others that are intended control another of the amputee&#39;s remaining limbs. 
     Other nerve interfaces have utilized a plurality of needle-like protrusions that are each surgically inserted into individual nerve fibers included in a nerve bundle. Each inserted protrusion acts as a contact that directly senses the signal transmitted by its respective nerve fiber, and is connected to its own dedicated wire that transmits the sensed signals externally of the amputee to a prosthetic controller. Such an interface is invasive, exposing the affected nerve fibers to damage from the surgical procedure to insert the protrusions. Further damage to the nerve is also possible due to the tethering forces required necessarily exerted on the nerve to support a large number of wires corresponding to the number of individual protrusions. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, there is a need in the art for a method and apparatus for monitoring electrical activity in a nerve. Such a method and apparatus can discriminate between electrical signals conducted by different regions of the nerve, be robust, and minimize forces imparted on the nerve to ensure the relationship between the apparatus and nerve is maintained. 
     According to one aspect, the subject application involves an electrode for monitoring electrical activity in different regions of a nerve. The electrode includes a cuff formed from a chronically-implantable material that, when implanted, extends at least partially around an external periphery of the nerve. Two or more contacts are supported by the cuff to be arranged adjacent to the different regions of the nerve along a transverse direction of the nerve when the cuff is implanted. A multiplexer is coupled to the cuff to be implanted for receiving electrical signals introduced to the contacts by the nerve and multiplexing, in vivo, the electrical signals to be transmitted to an external receiver over a shared communication channel. 
     According to another aspect, the subject application involves a method of monitoring electrical activity in a nerve of a subject. The method includes receiving electrical signals introduced to a plurality of contacts chronically implanted in the subject and arranged adjacent to different regions of an exterior periphery of the nerve. The signals introduced are manipulated, within the subject, for transmission over a common communication channel that is shared for transmission of the electrical signals introduced to each of the contacts. After the manipulation occurs, the manipulated signals are transmitted over the common communication channel to be received by a receiver that controls operation of a prosthetic device being worn by the subject. 
     According to another aspect, the subject application involves a method of fabricating an electrode for monitoring electrical activity along a nerve. The method includes arranging a plurality of insulated wires into substantially parallel arrangement with each other. Each of the insulated wires includes an electrical conductor, which can optionally be a stranded conductor, protected by an insulating material. The separation between the electrical conductor provided to a first insulated and the electrical conductor provided to a second insulated wire, which is immediately-adjacent to the first insulated wire, is limited to a distance established by the insulating material provided to the first and second insulated wires. The insulated wires are then heated to fuse the insulating material provided to the first and second insulated wires together. An aperture is formed in the insulating material provided to each of the insulated wires to expose a portion of each electrical conductor and form a contact for introducing an electrical signal conducted by the nerve to the electrical conductor. 
     According to another aspect, the subject application involves method of mitigating an effect of an external stimulation on electrical activity monitored along a nerve of a subject. The method according to this aspect includes, with an electrode implanted in the subject, receiving an instruction that an electrical signal is to be introduced to a target region of the nerve as the external stimulation. Signals introduced to the plurality of contacts provided to the electrode are received from different regions of the nerve at a time other than when the electrical signal is to be introduced to the target region. Within the subject, the received signals are manipulated to prepare information represented by the received signals for transmission over a common, shared communication channel. The method also includes interfering with consideration of another signal introduced to the plurality of contacts at a time when the electrical activity along the nerve is affected by the external stimulation during the manipulation. The information represented by the plurality of signals is transmitted over a common, shared communication channel to be received by a receiver, which can optionally be an external receiver. 
     The above summary presents a simplified summary in order to provide a basic understanding of some aspects of the systems and/or methods discussed herein. This summary is not an extensive overview of the systems and/or methods discussed herein. It is not intended to identify key/critical elements or to delineate the scope of such systems and/or methods. Its sole purpose is to present some concepts in a simplifies form as a prelude to the more detailed description that is presented later. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWING 
       The invention may take physical form in certain parts and arrangement of parts, embodiments of which will be described in detail in this specification and illustrated in the accompanying drawings which form a part hereof and wherein: 
         FIG. 1  shows a first perspective view of an illustrative embodiment of an electrode implanted in a residual limb and coupled to a nerve; 
         FIG. 2  shows a second perspective view of an illustrative embodiment of an electrode implanted in a residual limb and coupled to a nerve; 
         FIG. 3  shows a partially cutaway view taken along line  3 - 3  in  FIG. 1 ; 
         FIG. 4  shows a block diagram schematically depicting portions of a processor for manipulating signals to be transmitted over a shared communication channel to an external receiver; 
         FIG. 5  shows steps of an illustrative embodiment of a method of forming an electrode; 
         FIG. 6  shows an end view of immediately-adjacent insulated wires arranged to be formed into an array of contacts; and 
         FIG. 7  shows an illustrative embodiment of a stimulator for controlling introduction of an external stimulation to a nerve. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Certain terminology is used herein for convenience only and is not to be taken as a limitation on the present invention. Relative language used herein is best understood with reference to the drawings, in which like numerals are used to identify like or similar items. Further, in the drawings, certain features may be shown in somewhat schematic form. 
     It is also to be noted that the phrase “at least one of”, if used herein, followed by a plurality of members herein means one of the members, or a combination of more than one of the members. For example, the phrase “at least one of a first widget and a second widget” means in the present application: the first widget, the second widget, or the first widget and the second widget. Likewise, “at least one of a first widget, a second widget and a third widget” means in the present application: the first widget, the second widget, the third widget, the first widget and the second widget, the first widget and the third widget, the second widget and the third widget, or the first widget and the second widget and the third widget. 
       FIG. 1  shows an illustrative embodiment of an electrode  10  for monitoring electrical activity along a nerve  12 , which is schematically depicted and partially cutaway in  FIG. 1  for illustrative purposes. The nerve  12  conducts electrical signals from the brain through different regions, referred to generally at  14 , to control movements of a person&#39;s limbs. Thus, electrical signals conducted through a first region  14 A may control finger movement while electrical signals conducted through a second region  14 B may control wrist articulation, for example. 
     As shown in  FIG. 1 , the electrode  10  includes a cuff  16 , which can optionally be in the form of an elongated band, that is chronically implantable in a person to extend at least partially, and optionally entirely, about an external periphery of the nerve  12 . Rather than causing a portion of the contacts  20  to protrude into an interior of the nerve  12 , the contacts  20  can optionally all be arranged adjacent to different exterior regions spaced apart in a transverse direction of the nerve. The cuff  16  extends a suitable extent about the nerve  12 , when implanted, to interfere with separation of the cuff  12  from the nerve  12  when subjected to forces urging the cuff  16  away from the nerve  12  under normal usage. For instance, a plurality (four (4) in the illustrative embodiment shown in  FIGS. 1 and 2 ) wires  18  extend outwardly from the electrode  10  to facilitate communications between the electrode  10  and external devices as described below. Such wires  18  may be suspended from the electrode  10  or may otherwise exert forces on the electrode  10  when a residual limb in which the nerve  12  is located is moved. 
     The cuff  16  is said to be chronically implantable to couple the electrode  10  to the nerve  12 . Chronic implantation requires a surgical procedure to be performed to install the cuff  16  on the nerve  12  and remove the cuff  16  from the nerve  12 . In other words, to be considered chronic the implantation of the electrode  10  must be a long-term solution instead of a temporary implantation, where a target removal date is anticipated when a medical condition subsides. 
     As a chronically-implantable device, the cuff  16  can be formed from a material that is generally inert to substances likely to be encountered within a human body. Such a material can optionally be approved by a regulatory body such as the U.S. Food and Drug Administration (“FDA”) for implantation, long term or at least short term, in a human body. Examples of such a material include, but are not limited to flexible and biocompatible materials such as: medical grade silicone, polyether ether ketone, polytetrafluoroethylene, poly(methyl methacrylate), polyethylene, and the like. 
     The cuff  16  can support a plurality of contacts  20  at locations where the contacts  20  will be arranged to sense electrical signals transmitted by a plurality of the different regions  14  of the nerve  12 . The peripheral nervous system carries sensory and motor information that could be useful as command signals for function restoration in areas such as neural prosthetics and Functional Electrical Stimulation. The contacts  20  provide a robust interface for recording such electrical signals transmitted along the nerve  12 . 
     As shown in  FIGS. 1 and 2 , for example, the contacts  20  are to be positioned adjacent to the external periphery of the nerve  12 , extending along a transverse direction of the nerve  12  when the cuff  16  is implanted. In such an arrangement the contacts  20  can sense electrical signals conducted by each of the various different regions  14 A,  14 B. The sensed electrical signals transmitted through the contacts  20  allow a recipient controller to distinguish, along the transverse direction, electrical signals sensed in the region  14 A from electrical signals sensed in the region  14 B based on which of the contact(s)  20  sensed the electrical signals, and optionally a quality such as the magnitude of the voltage and/or current of the electrical signal sensed by a plurality of the contacts  20 . 
     Shown clearly in  FIG. 3 , the different regions  14  of the nerve  12  that conduct electrical signals to be sensed by the contacts  20  can be located at different vertical (according to the perspective shown in  FIG. 3 ) locations within the nerve  12 , as well as being distributed horizontally in the transverse direction. To distinguish between electrical signals conducted by a region  14 C at a relatively-low elevation from electrical signals conducted by a region  14 D at a relatively-high elevation, the contacts  20  can be supported by the cuff  16  to be positioned on opposite sides (e.g., above and below) of the nerve  12 . 
     Referring once again to  FIGS. 1 and 2 , each contact  20  is operatively connected to an input terminal  22  of a processor  24  forming a portion of a control unit  26  that is supported by the cuff  16 . An insulated wire  28  can be provided, and optionally, dedicated to form a conductive pathway between each contact and a respective input terminal  22  to convey signals induced in the contacts  20  by electrical signals conducted by the nerve  12  to the processor  24 . The insulated wires  28  can each include a stranded conductor formed from a plurality of corrosion-resistant wire filaments protected within a sheath formed of an electrically-insulating material. The corrosion resistance can be achieved through the use of materials such as a metal or metal alloy approved by the FDA for implantation, such as, platinum, gold, a steel alloy (commonly referred to as “stainless steel”) having a chromium content sufficient to resist oxidation and other forms of corrosion within the human body, and the like. Each of the wire filaments can be wound together, and optionally braided or otherwise arranged into a desired patter within the insulating material to ensure electrical continuity between each of the wire filaments of an insulated wire  28 . Although the conductive pathways are described herein as embodied by insulated wires  28  for purposes of describing the present technology, it is to be understood that printed conductive pathways formed by conventional lithographic techniques and conductive pathways formed from sheets of electrically-conductive materials are also encompassed by the present disclosure. 
     Signals induced in the contacts  20  by electrical signals transmitted through regions  14  of the nerve  12  are conducted to the processor  24 , where the signals are manipulated before being transmitted to an external receiver. An electrical signal conducted by one of the regions  14  can induce a signal in at least one, and optionally a plurality of the contacts  20 . At least one quality such as the magnitude of the voltage of the signal induced in the contacts  20  will be a function of the proximity of each contact  20  relative to the region  14  conducting the electrical signal. Accordingly, based on the contacts  20  in which the signal is induced and the relative properties (e.g., the voltage magnitude) of the signal induced in each contact  20 , the region  14  through which the electrical signal was conducted can be determined. 
     The control unit  26  is chronically implantable, and is to be coupled to the nerve  12  by e cuff  16  to manipulate the signals induced by electrical signals conducted by the nerve  12  before the manipulated signals are transmitted to the external receiver. As such, the control unit  26  can be enclosed within, and optionally hermetically sealed by a housing  30  to protect circuitry forming the processor  24  from the elements within the environment in which the electrode  10  is implanted. The housing  30  can optionally be formed from same material used for the cuff  16 , or can optionally be formed from any material approved for chronic implantation that isolates the circuitry of the control unit  26  from the ambient environment of the implantation site. 
     The external receiver to which the manipulated signals are to be transmitted from the control unit  26  can optionally translate those signals into commands for controlling a mechanized prosthetic device or paralyzed limbs. As such, the external receiver is to be disposed externally of the residual limb (e.g., outside the body) in which the electrode  10  is implanted, and can optionally be provided to the prosthetic device. 
     The processor  24  can be implemented as a hard-wired, dedicated arrangement of circuit components, as a computer processing component executing computer-executable instructions stored in a non-transitory computer-readable medium (e.g., solid-state flash memory, hard drive, etc. . . . ), or a combination thereof. The method of manipulation, performed in vivo by the implanted control unit  26 , can also optionally be defined by computer-executable instructions stored in a non-transitory computer-readable medium. 
     Regardless of its configuration, the processor  24  is operable to receive the signals induced in the plurality of contacts  20  and manipulate, in vivo, the received signals for transmission of the information carried by the manipulated signals over a common, shared communication channel. Manipulation of the signals can involve multiplexing the received signals, time shifting the received signals, or otherwise processing the signals received by the processor  24 . Such manipulation allows the information conveyed by each signal received from a plurality of the different contacts  20  to be transmitted to the external receiver over the same wire  18 , the same wireless network, or other shared communication channel over which one or more signals indicative of electrical activity occurring at a plurality of different regions  14  of the nerve  12  is transmitted to the external receiver. The shared communication channel, whether a hard-wired connection via the wire(s)  18  or via a wireless network connection via an antenna and transmitter provided to the electrode  10 , for example, is commonly used for each such transmission to minimize the number of dedicated connectors such as the wires  18  extending outwardly, away from the electrode  10 . Additionally, the tow-power signals induced in the contacts  20  by electrical activity in the different regions  14  of the nerve  12  can optionally be amplified before being manipulated to promote accurate communication of the received signals. After the signal manipulation occurs, the manipulated signal can be transmitted from the residual limb where the electrode  10  is implanted over the common communication channel to be received by the external receiver for controlling operation of a prosthetic device. 
     An illustrative example of the processor  24  is represented by the functional block diagram of  FIG. 4 . For the embodiment shown, the plurality of different contacts  20  are individually referred to at  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N, where N represents any desired integer number of contacts  20 . Although at least four (4) contacts  20  are shown in  FIG. 4  for illustrative purposes, it is to be understood that N can represent any desired number of contacts greater than or equal to two (2). 
     In addition to the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N a reference contact  32  can be operatively connected to the processor  24  to provide a reference signal against which the signal received from each of the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N for purposes of amplification. The reference contact  32  can span a significant portion (e.g., more than half the distance of the nerve  12  in the transverse direction) of the nerve  12  along which the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N are arranged. Amplifying only those signals induced in the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N that exceed any baseline signals induced in the reference contact  32  by a predetermined magnitude can limit the noise introduced to the manipulated signal to be transmitted to the external receiver. 
     Each intersection (such as the intersections referred to at  34 ) between a border of the processor  24  in  FIG. 4  and another line schematically represents an electrical connection to a terminal such as the input terminals  22  of the processor  24 . Likewise, each intersection between the wires  18  and the border of the processor  24  in  FIG. 4  represent an electrical connection to other terminals of the processor  24 . For instance, the intersection  36  can be a single pin, surface mount pad or other suitable connector to which one of the wires  18  can be electrically connected for conducting the manipulated signal from the implanted electrode  10  to the external receiver. Similarly, the intersections  38  can represent power and ground terminals for supplying a DC or other suitable power signal to facilitate operation of the processor  24  and other components provided to the control unit  26 . And the intersection  40  can represent a control terminal for inputting or otherwise communicating control signals governing operation of a multiplexer  42  or other component of the processor  24  responsible for manipulation of the signals received by the processor from the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N. 
     One example of the signal manipulation that can be performed by the processor  24  for transmitting the signals from the electrode  10  via a shared communication channel is multiplexing. Referring once again to the embodiment shown in  FIG. 4 , the signals induced in the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N that are adjacent to the regions  14  of the nerve  12  where electrical activity has occurred is delivered, via the insulated wires  28 , to respective input terminals  22  of the process  24 . The signal received at each input terminal  22  relative to a baseline signal input induced in the reference contact  32  is amplified by an amplification stage  44  electrically connected to each input terminal  22 . 
     The amplified signals from the plurality of different contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N is received by a multiplexer  42  of the processor  24 , which combines the information represented by the signals received from the plurality of different contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N into a single, multiplexed signal, in vivo. The embodiment shown in  FIG. 4  is a N-to-1 analog multiplexer  42 , meaning that a single multiplexer  42  is capable of manipulating analog signals received by all of the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N. An example of a processor  24  provided with a suitable multiplexing component is the RHA2000 series multi-channel bioamplifier chip (e.g., RHA2116) offered by Intan Technologies LLC. However, alternate embodiments can include a plurality of multiplexers  42  to distribute the multiplexing load, where each such multiplexer  42  multiplexes fewer than all of the signals from all of the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N. For such embodiments, there may be a plurality of shared communication channels over which multiplexed signals are transmitted to one or more external receivers. Further, the multiplexer  42  can optionally multiplex digital signals rather than analog signals without departing from the scope of the present disclosure. Once the signals from the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N have been multiplexed, the multiplexed signal is then transmitted from the electrode  10  over the single wire  18  in the embodiment of  FIG. 4  from the residual limb where the electrode is implanted to be received by the external receiver. At the external receiver, the multiplexed signals is demultiplexed and interpreted for controlling the prosthetic device, for example. 
     Although only a single wire  18  is used as the shared communication channel in the embodiment of  FIG. 4 , the number of shared communication channels over which multiplexed signals are output to the external receiver(s) can be any number less than the number of contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N. For instance, a ratio of at least four (4) contacts to every shared communication channel, or optionally at least sixteen (16) contacts to every shared communication channel, can be established. Sharing a communication channel reduces that number of wires, for example, that would otherwise be required to establish a dedicated communication channel for each contact  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N, to output each respective signal separately. Sharing at least one communication channel reduces the forces urging separation of the electrode  10  from the nerve  12  that would otherwise be imparted by providing a dedicated communication channel for each of the  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N. Thus, regardless of the number of multiplexers  42 , there are fewer communication channels utilized for transmitting multiplexed signals to an external receiver than contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N sensing electrical activity in the nerve  12 . So for the embodiment shown in  FIG. 4 , a total of four (4) wires  18 : DC power supply, ground, control and the single shared communication channel can extend from the electrode  10  and the residual limb where the electrode  10  is implanted. 
     Although the detailed description of the signal manipulation herein is focused on multiplexing the received signals to be transmitted over the shared communication channel, any technique of adapting signals for transmission over a shared communication channel can be used. For instance, introducing a delay to one or more signals to allow each separate signal to be transmitted serially over the shared communication channel can be utilized instead of multiplexing. 
     The multiplexer  42  can optionally output the manipulated signal for transmission to the external receiver in analog form or, alternately, as a digital signal. For embodiments where the manipulated signal is transmitted from within the residual limb or other location where the electrode  10  is implanted as a digital signal, the control unit  26  can also optionally include an analog-to-digital converter (“ADC”)  45  to convert the analog signal into a digital signal. As shown in  FIG. 4 , the ADC  45  is arranged to convert the manipulated signal output by the multiplexer  42 . The digital signal from the ADC  45  is then output via a single wire  18 B, for example, which is operable as the shared communication channel of the present embodiment to be conveyed to the external receiver. 
     Although the embodiment shown in  FIG. 4  includes an ADC  45  that converts the manipulated signal output by the multiplexer  42  into a digital signal, it is to be understood that the ADC  45  can be operatively arranged at any desired location between the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N and the shared communication channel that transmits the manipulated signal from the residual limb or other location where the electrode  10  is implanted. For instance, the ADC  45  can be operatively disposed to convert analog signals from the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N into digital signals before the digital signals are manipulated by the multiplexer  42 . For such embodiments, an ADC  45  can optionally be dedicated to convert the signals introduced to each respective contact  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N. 
     The control unit  26  can optionally also include a stimulator  47 , an embodiment of which is schematically depicted in  FIG. 7 . The stimulator  47 , or portions thereof, can optionally be integrated as part of the processor  24 , and can optionally include hardware components and/or computer-executable instructions also utilized to convey the signals introduced to the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N over the shared communication channel. Regardless of its configuration, the stimulator  47  receives an instruction transmitted by the external receiver or other stimulation controller to deliver an electric signal to one or more regions  14  of the nerve  12  via respective contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N arranged adjacent to those regions  14  targeted. Introducing the electrical signals from the stimulator  47  via the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N to the respective regions  14  of the nerve  12  can simulate a sensory perception such as touch via the nerve  12  that would otherwise require a sensory signal transmitted by an amputated limb, for example. 
     To explain operation of the stimulator  47 , an illustrative example will be described as receiving a sensory signal indicative of a touch sensed by a prosthetic device, and delivering electrical stimulation to the regions  14  of the nerve  12  that would otherwise be stimulated by a limb replaced by the prosthetic device. However, it is understood that other external sources such as signal generators, etc. . . . can be the source of the instruction to electrically stimulate one or more of the regions  14  of the nerve  12 . Additionally, the electrical stimulation is not necessarily performed to simulate a sensory perception, but can be performed as part of a therapeutic or other treatment involving nerve stimulation. 
     As shown in  FIG. 7 , the demultiplexer  49  receives the instruction signal, which is indicative of the contact sensed by the prosthetic device as the external source, via the single wire  18  or other shared communication channel. The instruction encodes at least one of: the identity of the one or more of the contacts  201 ,  20 - 2 ,  20 - 3 , . . .  20 -N that are to conduct the stimulation signal to the respective nerve regions  14  of the nerve  12 , the shape of the stimulation signal to be conducted by the selected contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N, a power of the stimulation signal to be conducted, a timing of the stimulation signal to be delivered to the nerve  12  via each selected contact  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N, and a notification that external stimulation of the nerve  12  (or another nerve as described below) is being performed to mitigate the effect of such stimulation on the signals introduced to the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N that are to be manipulated as described above by the electrode  10 . 
     The demultiplexer  49  interprets the instruction signal and identifies the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N through which the stimulation signal is to be delivered to the nerve  12 . The demultiplexer  49 , in turn, transmits the information indicative of the signal to a waveform component  51  that can optionally be included to establish a desired waveform of the stimulation signal to be delivered to the nerve  12  through a respective contact  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N. The waveform component  51  can include circuitry or other hardware and optionally embedded or other computer-executable instructions that, when executed, allow the waveform component  51  to govern operation of a respective switching component  55  to selectively connect the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N to a power supply  57  (V DD  in the present example) and generate the desired waveform. 
     Each switching component  55  can include a solid-state, electronically-actuated switch such as a transistor or other device operable to selectively open and close a conductive pathway between the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N and the power supply  57 . Although the power supply  57  is shown in the present example as the voltage V DD  input via the wire  18  for powering the processor  24 , alternate embodiments of the power supply  57  can include an on-board power supply such as a rechargeable battery provided to the control unit  26 . Regardless of the nature of the power supply  57 , the power supply  57  can supply a suitable electric current and voltage to effectively stimulate the regions  14  of the nerve  12 . 
     As mentioned above, the instruction signal received by the demultiplexer  49  can include a notification that external stimulation of the nerve  12  (or another nerve) is being performed. Since the contacts  201 ,  20 - 2 ,  20 - 3 , . . .  20 -N are also used for sensing electrical activity in the nerve  12  to be transmitted externally, it is conceivable that artifacts or other noise resulting from the external stimulation of the nerve  12  could be introduced to the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N that are not involved in the external stimulation. Such contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N that are not involved in an external stimulation of the nerve  12  by the electrode are referred to hereinafter as “inactive contacts”. The inactive contacts may reside on the electrode  10  being used to perform the external stimulation or another electrode  10  coupled to a different nerve, or a different branch of the same nerve  12 . But regardless of the electrode  10  on which they reside, the inactive contacts can optionally be isolated from portions of the processor  24  such as the multiplexer  42 . According to alternate embodiments, any signals introduced to the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N that are inactive contacts when an external stimulation is being performed can be excluded, or otherwise ignored to avoid affecting the manipulated signal output by the multiplexer  42  and transmitted over the shared communication channel to the external receiver. In other words, the effect of the external stimulation introduced by the electrode  10  or another electrode implanted at a location where such external stimulation affects the signals introduced to the electrode  10  can be excluded from the manipulated signal transmitted via the shared communication channel to the external receiver. Such artifacts are not indicative of signals conducted by the nerve  12  in response to a control signal from the brain, but indicative of the external stimulation, and can be excluded from consideration in generating the manipulated signal to be transmitted from the electrode  10  over the shared communication channel to the external receiver. 
     The notification received by the stimulator  47  can include at least one of: a time when external stimulation is to be performed, information indicative of the one or more electrodes that are to perform the external stimulation, and information that can be used to identify the inactive contacts. For embodiments where the inactive contacts are electrically isolated from other circuit components, the respective switching component  55  of each inactive contact can be operable to isolate the respective contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N from the multiplexer  42  in addition to selectively conducting the stimulation signal to the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N. Each switching component  55  provided to an electrode  10  that is to perform external stimulation of the nerve  12  can be adjusted to a state that isolates the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N from the multiplexer  42  during performance of the external stimulation to avoid conducting artifacts resulting from external stimulation to the multiplexer  42 . 
     According to alternate embodiments, the control unit  26  of the electrode  10  can optionally receive information indicating that external stimulation of the nerve  12  is to be performed by another electrode that can affect the electrical activity along that nerve  12 . For example, external stimulation is to be performed using an electrode provided to a trunk region of the nervous system from which the nerve  12  is branched. Such information can also optionally include timing information that allows the control unit  26  that received the information to isolate the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N or otherwise exclude from consideration in generating the manipulated signal any signals introduced to the contacts  20 - 1 ,  20 - 2 ,  20 - 3 , . . .  20 -N when such external stimulation occurs. 
     A method of fabricating the electrode  10  can be understood with reference to  FIG. 5 . Each contact  20  and wire  28  establishing the conductive pathway between the contacts  20  and the processor  24  can be formed from a single segment of an electrically conductive material, such as printed conductors, thin films of a conductive material, and stranded, and optionally braided stainless steel conductor  56 , shown in the end view of immediately-adjacent wires  28  in  FIG. 6 , coated in Polytetrafluoroethylene (“PTFE”), for example, or other suitable electrically insulating material  58 . A plurality of such wires  28 , corresponding to the number of contacts  20  needed, are arranged and optionally tightly packed side by side (i.e., parallel with each other) in a single row at step S 100  in  FIG. 5 . Arranging the wires  28  so they are touching each other in such a parallel orientation limits the distance D, shown in  FIG. 6 , separating the stranded conductor  56  in immediately adjacent (i.e., touching) wires  28  to a distance D equal to twice the thickness T of the insulating material  58  protecting the stranded conductors  56  of those wires  28 . And since the thickness T of the insulating material of each wire  28  is approximately the same, even if the wires  28  are arranged by hand instead of by an automated machine, substantially equal spacing of the neighboring stranded conductors  56  (and resulting contacts  20 ) can be achieved. 
     At step S 110  in  FIG. 5 , a suitable amount of heat is applied to fuse the insulating material  58  of the immediately-adjacent wires  28  together. Fusing the insulating material  58  maintains the relative arrangement of each of the wires  28  but allows a degree of flexibility to bend about an axis extending in the transverse direction, indicated by arrow  46  in  FIG. 5 , of the wires  28 . 
     A heated filament, hot knife or other suitable stripping device  52  can then be used at step S 120  to strip a portion of the insulating material from each wire  28  to form an aperture  48  in the insulating material  58  provided to each of the wires  28 . A portion  50  of each stranded conductor  56  is exposed as a result, and forms the contact  20  for each respective wire  28  in which a signal is to be induced by electrical activity in the nerve  12 . Each resulting contact  20  can optionally be aligned in the transverse direction  46 , perpendicular to a longitudinal axis of the wires  28 , and the plurality of contacts  20  can extend entirely across the arrangement of wires  28 . A silicone-based sealant or other suitable electrical insulator  60  can be applied at step S 130  to a terminal end  62  of the plurality of insulated wires  28  adjacent to the aperture  48  formed in the insulating material  58 . The opposite end  64  of the stranded conductors  56  can be electrically connected to the input terminals  22  of the processor  24  for delivering the signals induced in the contacts  20  to the processor  24  to be manipulated. 
     Depending on the use, this array of contacts  20  can be received in a housing  62  forming the cuff  16  to be implanted. According to one example, a sheet of silicone with a polyimide stiffener was arranged to sandwich the array of contacts  20  there between at step S 140 . The silicon sheets can be sealed together about the array of wires  28  using an adhesive. According to alternate embodiments, the array of wires  28  can optionally be included in an injection molder and the silicon injection molded about the array. 
     Illustrative embodiments have been described, hereinabove. It will be apparent to those skilled in the art that the above devices and methods may incorporate changes and modifications without departing from the general scope of this invention. It is intended to include all such modifications and alterations within the scope of the present invention. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is interpreted when employed as a transitional word in a claim.