COATINGS

This application is being filed on 28 December 2017, as a PCT International patent application, and claims priority to U.S. Provisional Patent Application No. 62/543,205, filed August 9, 2017, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION In known therapy systems, implantable devices are used to deliver electrical therapy signals to an internal anatomical feature, such as a nerve, of a patient. Such systems include implantable devices having electrodes that are applied directly to the anatomical feature and deliver current thereto. In such systems, the electrodes have low impedance values, such as approximately 400 Ohms, and low capacitance values, thereby allowing current to leak through the electrodes and flow to the targeted nerve. Because of the constant current leak, such systems consume a high degree of power, thereby affecting battery life of the implantable device.

SUMMARY OF THE INVENTION According to one aspect of the disclosure, a therapy system is disclosed for applying therapy to an internal anatomical feature of a patient. The system includes at least one electrode coated with, but not limited to, low conducting carbon nanotubes (CNTs) and/or low conductive polymers for implantation within the patient and placement at the anatomical feature (e.g., a nerve) for applying the therapy signal to the feature upon application of a treatment signal to the electrode. An implantable component is placed in the patient's body beneath a skin layer and coupled to the electrode for delivery of an electrical signal using a selected current or a selected voltage. The signal may be monophasic or biphasic. The implantable component includes an implanted antenna. An external component has an external antenna for placement above the skin and adapted to be electrically coupled to the implanted antenna.

In embodiments, a system for applying therapy to a target nerve of a subject comprises at least two electrodes, each having a low conductive CNT and/or polymer coating with an impedance of at least 2000 ohms configured to be implanted within a body of the subject and placed at the target nerve, an implantable component for placement in the body of the subject, the implantable component being configured to generate an electrical signal at a selected voltage or a selected current, wherein the electrical signal is selected to modulate activity on the target nerve, the implantable component being coupled to an implanted antenna; an external component including an external antenna configured to be placed above the skin layer and adapted to communicate with the implanted antenna. In embodiments, the system further comprises an external programmer configured to

communicatively couple to the external component, the external programmer being configured to provide therapy instructions to the external component, wherein the external component is configured to send the therapy instructions to the implantable component via the external antenna and the implanted antenna.

Another aspect of the disclosure provides a method of treating a disorder in a subject comprising applying an electrode to a target nerve, wherein the electrode has a low conductive CNT and/or polymer coating with an impedance of at least 2000 ohms and is operatively coupled to an implantable neuroregulator; applying a therapy cycle to the target nerve, wherein the therapy cycle comprises applying an electrical signal at a selected current or selected voltage to the electrode

intermittently, and is selected to downregulate or upregulate activity on the target nerve.

In embodiments, a method of treating a disorder in a subject comprises applying at least two electrodes to a target nerve, wherein each electrode has a low conductive CNT and/or polymer coating with an impedance of at least 2000 ohms and is operatively coupled to an implantable neuroregulator; and applying a therapy cycle to the target nerve, wherein the therapy cycle comprises applying an electrical signal at a selected voltage or selected current to the electrode intermittently, wherein the electrical signal is selected to modulate activity on the target nerve.

In embodiments, target neuronal tissue is selected from the group consisting of the vagus nerve, sacral nerves, pudendal nerve, renal plexus, thoracic splanchnic nerves, glossopharyngeal nerve, facial nerve, dorsal roots, dorsal column of the spinal cord, subthalamic nucleus, globus pallidus, thalamus motor cortex and brodmann Area 25. In embodiments, the disorder is selected from the group consisting of obesity, metabolic syndrome, diabetes, hypertension, inflammatory bowel disease, pancreatitis, bulimia, chronic pain, movement disorders, seizures, depression, obsessive compulsive disorder, cardiac conditions, cardiac hypertension, and incontinence. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a therapy system having features that are examples of inventive aspects of the principles of the present invention, the therapy system including a neuroregulator and an external charger;

FIG. 2A is a plan view of an implantable neuroregulator for use in the therapy system of FIG. 1 according to aspects of the present disclosure;

FIG. 2B is a plan view of another implantable neuroregulator for use in the therapy system of FIG. 1 according to aspects of the present disclosure.

FIG. 3 A is a block diagram of a representative circuit module for the neuroregulator of FIG. 2 A and FIG 2B according to aspects of the present disclosure;

FIG. 3B is a block diagram for a low power arbitrary waveform generator intended for implantable therapeutic devices. Some of the functionality is optional such as the memory and telemetry blocks;

FIG. 4 is a block diagram of a circuit module for an external charger for use in the therapy system of FIG. 1 according to aspects of the present disclosure;

FIG.5 shows A) Plots of current versus time (i) and voltage versus time (ii) for a constant current device. Note that voltage quickly increases in (ii) due to current charging the capacitance of the nerve and electrode system. Then the voltage continues to rise slowly due to current charging the electrode to nerve capacitance;

B) Plot of voltage versus time (i) and current versus time (ii and iii) for a constant voltage device with low (ii) and high (iii) impedance electrodes. Note that following the initial current spike in (ii) charging the capacitance of the nerve and electrode system, the remaining current will be essentially determined by the parallel resistance of the nerve. In (iii) the current goes down to a lower level due to the additional resistance of the electrode to nerve interface.

C) Vectors representing the resistance (R), capacitance (C) and impedance (Z) of uncoated (i) versus coated (ii) electrodes. Note the large increase in resistance with the coated electrodes. FIG. 6 Schematic representing a graphene sheet with chiral vectors which connects the two lattice points from (0,0 ) to (n _1? n ₂ ) . Examples of ni and n ₂ coordinates and the conductivity of folding the graphene sheet from (0, 0) to these coordinates is also displayed on the schematic. The folding of the graphene sheet produces a CNT.

FIG. 7 Schematic of an electrode (300) which is comprised of a conductive surface coated with a low conductive polymer (302) and then a limited conductive CNT layer (304).

FIG. 8 illustrates a method for applying a treatment to a nerve using two or more electrodes coated with high impedance CNTs.

DETAILED DESCRIPTION

In embodiments, methods and systems involve using conductive electrodes coated with low conducting CNTs and/or low conducting polymers to establish an electrical field across the nerve. Since the electrode is insulated the amount of field sustaining current is minimized. In this case, current charges the electrode capacitance with very little current flowing through the nerve. The applied voltage differential would surround the nerve driving voltage gated channels on individual cells open or closed. In this case, a voltage is applied to first charge the capacitance of the electrode. Following this, little current is flowing through the nerve because the electrodes are coated with a limited-conductive CNT and/or polymer material which minimizes the amount of field sustaining current resulting in energy savings and increased safety. This is different from traditional methods using a low impedance electrode with the requirement of large currents flowing through the resistance of the nerve to induce a voltage differential. Use of a low conducting coated electrode nerve interface provides an electrical field that can be sustained using a very low charge.

The application of such electrodes has wide applicability to a number of conditions employing electric signals to modulate nerve activity. For example, systems having a voltage or current regulated source with high impedance electrodes are useful in the application of an electrical signal to at least partially downregulate activity on a target nerve such as the vagus nerve, renal nerve, celiac nerve, cranial nerves and splanchnic nerve. In other embodiments, the signal may upregulate activity on a target nerve such as the glossopharyngeal nerve and baroreceptors. The signal may also modulate activity of neuronal tissue of the subthalamic nucleus, globus pallidus, thalamus motor cortex and brodmann Area 25. Modulation of activity on the target nerve can be used to treat a variety of conditions such as obesity, diabetes, hypertension, metabolic conditions, pancreatitis, inflammatory bowel disease, bulimia, dysmotility disorders, chronic pain, movement disorders, seizures, refectory depression, obsessive compulsive disorder, cardiac conditions, heart failure, and incontinence.

In embodiments, it is desirable to provide an implantable device that is able to deliver an electrical signal to a nerve to at least partially modulate the nerve activity while minimizing the power requirements. Minimizing the power requirements decreases the size of the battery allowing for construction of a smaller device, prolongs life of the battery in the device and requires shorter charging times for the battery. Use of an electrode that has high impedance CNT and/or polymer coating provides for application of an electric signal at a selected voltage or current with very low power requirements and with a low risk of any tissue damage.

Devices and methods are described herein that provide such an electrical signal.

With reference now to the various drawing figures in which identical elements are numbered identically throughout, a description of embodiments of the present disclosure will now be described.

A. Therapy System

FIG. 1 schematically illustrates a therapy system 100. The therapy system 100 includes a neuroregulator 104, an electrical lead arrangement 108, and an external charger 101. The neuroregulator 104 is adapted for implantation within a patient. As will be more fully described herein, the neuroregulator 104 typically is implanted just beneath a skin layer 103.

The neuroregulator 104 is configured to connect electrically to the lead arrangement 108. In general, the lead arrangement 108 includes two or more electrical lead assemblies 106, 106a. In embodiments, a single lead comprises at least two electrodes. In other embodiments, each lead comprises a single electrode. In the example shown, the lead arrangement 108 includes two identical (bipolar) electrical lead assemblies 106, 106a. The neuroregulator 104 generates therapy signals and transmits the therapy signals to the lead assemblies 106, 106a. The lead assemblies 106, 106a up-regulate and/or down-regulate nerves of a patient based on the therapy signals provided by the neuroregulator 104. In an embodiment, the lead assemblies 106, 106a include distal electrodes 212, 212a, which are placed on one or more nerves of a patient. For example, the electrodes 212, 212a may be individually placed on the anterior vagal nerve AVN and posterior vagal nerve PVN, respectively, of a patient. For example, the distal electrodes 212, 212a can be placed just below the patient's diaphragm. In other embodiments, however, fewer or more electrodes can be placed on or near fewer or more nerves. In embodiments, the electrodes have an impedance of at least about 2000 Ohms.

The external charger 101 includes circuitry for communicating with the implanted neuroregulator 104. In general, the communication is transmitted across the skin 103 along a two-way signal path as indicated by arrows A. Example communication signals transmitted between the external charger 101 and the neuroregulator 104 include treatment instructions, patient data, and other signals as will be described herein. Energy also can be transmitted from the external charger 101 to the neuroregulator 104 as will be described herein.

In the example shown, the external charger 101 can communicate with the implanted neuroregulator 104 via bidirectional telemetry (e.g. via radiofrequency (RF) signals). The external charger 101 shown in FIG. 1 includes a coil 102, which can send and receive RF signals. A similar coil 105 can be implanted within the patient and coupled to the neuroregulator 104. In an embodiment, the coil 105 is integral with the neuroregulator 104. The coil 105 serves to receive and transmit signals from and to the coil 102 of the external charger 101.

For example, the external charger 101 can encode the information as a bit stream by amplitude modulating or frequency modulating an RF carrier wave. The signals transmitted between the coils 102, 105 preferably have a carrier frequency of about 6.78 MHz. For example, during an information communication phase, the value of a parameter can be transmitted by toggling a rectification level between half-wave rectification and no rectification. In other embodiments, however, higher or lower carrier wave frequencies may be used.

In an embodiment, the neuroregulator 104 communicates with the external charger 101 using load shifting (e.g., modification of the load induced on the external charger 101). This change in the load can be sensed by the inductively coupled external charger 101. In other embodiments, however, the neuroregulator 104 and external charger 101 can communicate using other types of signals.

In an embodiment, the neuroregulator 104 receives power to generate the therapy signals from an implantable power source 151 (see FIG. 3 A), such as a battery. In a preferred embodiment, the power source 151 is a rechargeable battery. In some embodiments, the power source 151 can provide power to the implanted neuroregulator 104 when the external charger 101 is not connected. In other embodiments, the external charger 101 also can be configured to provide for periodic recharging of the internal power source 151 of the neuroregulator 104. In an alternative embodiment, however, the neuroregulator 104 can entirely depend upon power received from an external source. For example, the external charger 101 can transmit power to the neuroregulator 104 via the RF link (e.g., between coils 102, 105).

In embodiments, the neuroregulator can be powered by a rechargeable battery, which is periodically charged by the application of the mobile charger, the latter being placed in close proximity to the implanted neuroregulator. Alternatively, the neuroregulator can be directly powered by RF energy provided by the mobile charger. The choice of the mode of providing power is made via a setting of the mobile charger, or via the clinician programmer. In a further embodiment, charging of the rechargeable battery in the neuroregulator, can be achieved by application of remote wireless energy. (Grajski et al, IEEE Microwave Workshop series on Innovative Wireless Power Transmission:Technology, Systems, and Applications, 2012 published on a4wp.org).

In some embodiments, the neuroregulator 104 initiates the generation and transmission of therapy signals to the lead assemblies 106, 106a. In an embodiment, the neuroregulator 104 initiates therapy when powered by the internal battery 151. In other embodiments, however, the external charger 101 triggers the neuroregulator 104 to begin generating therapy signals. After receiving initiation signals from the external charger 101, the neuroregulator 104 generates the therapy signals and transmits the therapy signals to the lead assemblies 106, 106a.

In other embodiments, the external charger 101 also can provide the instructions according to which the therapy signals are generated (e.g., pulse-width, amplitude, and other such parameters). In a preferred embodiment, the external charger 101 includes memory in which individual parameters, programs, and/or therapy schedules can be stored for transmission to the neuroregulator 104. Selection of those parameters can be made by a user on a user interface. In embodiments, those parameters include pulse width, constant voltage settings, constant current settings, frequency, and electrode size. For example, for application to a nerve to be downregulated, one such program can involve selection of a frequency of about 200- 5000 Hz, selection of a constant voltage of about 1-20 volts, and selection of a variety of pulse widths ranging from about 10 microseconds to 100 microseconds. For example, for application to a nerve to be upregulated, one such program can involve selection of a frequency of about 200 Hz or less, selection of a constant voltage of about 1-20 volts, and selection of a variety of pulse widths ranging from about 10 microseconds to 100 microseconds. The external charger 101 also can enable a user to select a parameter/program/therapy schedule as displayed on a user interface, and then stored in memory for transmission to the neuroregulator 104. In another embodiment, the external charger 101 can provide treatment instructions with each initiation signal.

Typically, each of the parameters/programs/therapy schedules stored on the external charger 101 can be adjusted by a physician to suit the individual needs of the patient. For example, a computing device (e.g., a notebook computer, a personal computer, etc.) 107 can be communicatively connected to the external charger 101. With such a connection established, a physician can use the computing device 107 to program parameters and/or therapies into the external charger 101 for either storage or transmission to the neuroregulator 104.

The neuroregulator 104 also may include memory 152 (see FIG. 3 A) in which treatment instructions and/or patient data can be stored. For example, the neuroregulator 104 can store therapy programs or individual parameters indicating what therapy should be delivered to the patient. The neuroregulator 104 also can store patient data indicating how the patient utilized the therapy system 100 and/or reacted to the delivered therapy.

In what follows, the focus of the detailed description is the embodiment in which the neuroregulator 104 contains a rechargeable battery 151 from which the neuroregulator 104 may draw power (FIG. 3 A).

1. System Hardware Components

a. Neuroregulator

Different embodiments of the neuroregulator 104, 104' are illustrated schematically in FIGS. 2A and 2B, respectively. The neuroregulator 104, 104' is configured to be implanted subcutaneously within the body of a patient. In embodiments, the neuroregulator 104, 104' is implanted subcutaneously on the thoracic sidewall in the area slightly anterior to the axial line and caudal to the arm pit. In other embodiments, alternative implantation locations may be determined by the implanting surgeon.

Typically, the neuroregulator 104, 104' is implanted parallel to the skin surface to maximize RF coupling efficiency with the external charger 101. In an embodiment, to facilitate optimal information and power transfer between the internal coil 105, 105' of the neuroregulator 104, 104' and the external coil 102 of the external charger 101, the patient can ascertain the position of the neuroregulator 104, 104' (e.g., through palpation or with the help of a fixed marking on the skin). In an embodiment, the external charger 101 can facilitate coil positioning.

As shown in FIGS. 2 A and 2B, the neuroregulator 104, 104' generally includes a housing 109, 109' overmolded with the internal coil 105, 105', respectively. The overmold 110, 110' of the neuroregulator 104, 104' is formed from a bio-compatible material that is transmissive to RF signals (i.e., or other such communication signals). Some such bio-compatible materials are well known in the art. For example, the overmold 110, 110' of the neuroregulator 104, 104' may be formed from silicone rubber or other suitable materials. The overmold 110, 110' also can include suture tabs or holes 119, 119' to facilitate placement within the patient's body.

The housing 109, 109' of the neuroregulator 104, 104' also may contain a circuit module, such as circuit 112 (see FIG. 1, 3A, and 3B), to which the coil 105, 105' may be electrically connected along a path 105a, 105a'. The circuit module within the housing 109 may be electrically connected to a lead assembly, for example, the lead assemblies 106, 106a (FIG. 1) through conductors 114, 114a. In other embodiments, a single lead may be employed. In the example shown in FIG. 2 A, the conductors 114, 114a extend out of the housing 109 through strain reliefs 118, 118a. Such conductors 114, 114a are well known in the art.

The conductors 114, 114a terminate at connectors 122, 122a, which are configured to receive or otherwise connect the lead assemblies 106, 106a (FIG. 1) to the conductors 114, 114a. By providing connectors 122, 122a between the neuroregulator 104 and the lead assemblies 106, 106a, the lead assemblies 106, 106a may be implanted separately from the neuroregulator 104. Also, following implantation, the lead assemblies 106, 106a may be left in place while the originally implanted neuroregulator 104 is replaced by a different neuroregulator.

As shown in FIG. 2 A, the neuroregulator connectors 122, 122a can be configured to receive connectors 126 of the lead assemblies 106, 106a. For example, the connectors 122, 122a of the neuroregulator 104 may be configured to receive pin connectors (not shown) of the lead assemblies 106, 106a. In another embodiment, the connectors 122, 122a may be configured to secure to the lead assemblies 106, 106a using set-screws 123, 123a, respectively, or other such fasteners. In a preferred embodiment, the connectors 122, 122a are well-known IS-1 connectors. As used herein, the term "IS-1" refers to a connector standard used by the cardiac pacing industry, and is governed by the international standard ISO 5841-3.

In the example shown in FIG 2B, female connectors 122', 122a' configured to receive the leads 106, 106a are molded into a portion of the overmold 110' of the neuroregulator 104'. The leads connectors 126 are inserted into these molded connectors 122', 122a' and secured via setscrews 123', 123a', seals (e.g., Bal seals®), and/or another fastener.

The circuit module 112 (see FIGS. 1, 3A, and 3B) is generally configured to generate therapy signals and to transmit the therapy signals to the lead assemblies 106, 106a. The circuit module 112 also may be configured to receive power and/or data transmissions from the external charger 101 via the internal coil 105. The internal coil 105 may be configured to send the power received from the external charger to the circuit module 112 for use or to the internal power source (e.g., battery) 151 of the neuroregulator 104 to recharge the power source 151.

Block diagrams of example circuit modules 112, 112a are shown in FIGS.

3 A, 3B, respectively. Either circuit module 112, 112a can be utilized with any neuroregulator, such as neuroregulators 104, 104' described above. The circuit modules 112, 112a differ in that the circuit module 112a may be operated directly from a field programmable gate array(204), without the presence of a micro controller reducing its power consumption, and the circuit module 112 does not.

Power operation for circuit module 1 12 may be provided by the external charger 101 or by the internal power source 151. Either circuit module 112, 112a may be used with either neuroregulator 104, 104' shown in FIGS. 2 A, 2B. The circuit module 112 includes an RF input 157 including a rectifier 164. The rectifier 164 converts the RF power received from the internal coil 105 into DC electric current. Direct current can then be used to provide for a potential on the CNT coated high impedance electrode. Alternatively, alternating current can be used to provide a selectable but constant voltage or current. Circuitry for constant voltage or constant current devices is known to those of skill in the art.

For example, the RF input 157 may receive the RF power from the internal coil 105, rectify the RF power to a DC power, and transmit the DC current to the internal power source 151 for storage. In one embodiment, the RF input 157 and the coil 105 may be tuned such that the natural frequency maximizes the power transferred from the external charger 101.

In an embodiment, the RF input 157 can first transmit the received power to a charge control module 153. The charge control module 153 receives power from the RF input 157 and delivers the power where needed through a power regulator 156. For example, the RF input 157 may forward the power to the battery 151 for charging or to circuitry for use in creating therapy signals as will be described below. When no power is received from the coil 105, the charge control 153 may draw power from the battery 151 and transmit the power through the power regulator 160 for use. For example, a central processing unit (CPU) 154 of the neuroregulator 104 may manage the charge control module 153 to determine whether power obtained from the coil 105 should be used to recharge the power source 151 or whether the power should be used to produce therapy signals. The CPU 154 also may determine when the power stored in the power source 151 should be used to produce therapy signals.

The transmission of energy and data via RF/inductive coupling is well known in the art. Further details describing recharging a battery via an RF/inductive coupling and controlling the proportion of energy obtained from the battery with energy obtained via inductive coupling can be found in the following references, all of which are hereby incorporated by reference herein: U.S. Patent No. 3,727,616, issued April 17, 1973, U.S. Patent No. 4,612,934, issued September 23, 1986, U.S.

Patent No. 4,793,353, issued December 27, 1988, U.S. Patent No. 5,279,292, issued

January 18, 1994, and U.S. Patent No. 5,733,313, issued March 31, 1998.

In general, the internal coil 105 may be configured to pass data transmissions between the external charger 101 and a telemetry module 155 of the neuroregulator 104. The telemetry module 155 generally converts the modulated signals received from the external charger 101 into data signals understandable to the CPU 154 of the neuroregulator 104. For example, the telemetry module 155 may demodulate an amplitude modulated carrier wave to obtain a data signal. In one embodiment, the signals received from the internal coil 105 are programming instructions from a physician (e.g., provided at the time of implant or on subsequent follow-up visits). The telemetry module 155 also may receive signals (e.g., patient data signals) from the CPU 154 and may send the data signals to the internal coil 105 for transmission to the external charger 101.

The CPU 154 may store operating parameters and data signals received at the neuroregulator 104 in an optional memory 152 of the neuroregulator 104.

Typically, the memory 152 includes non-volatile memory, such as read-only memory. In other embodiments, the memory 152 also can store serial numbers and/or model numbers of the leads 106; serial number, model number, and/or firmware revision number of the external charger 101; and/or a serial number, model number, and/or firmware revision number of the neuroregulator 104.

The CPU 154 of the neuroregulator 104 also may receive input signals and produce output signals to control a signal generation module 159 of the

neuroregulator 104. Signal generation timing may be communicated to the CPU 154 from the external charger 101 via the coil 105 and the telemetry module 155. In other embodiments, the signal generation timing may be provided to the CPU 154 from an oscillator module (not shown). The CPU 154 also may receive scheduling signals from a clock, such as 32 KHz real time clock (not shown).

The CPU 154 forwards the timing signals to the signal generation module 159 when therapy signals are to be produced. The CPU 154 also may forward information about the configuration of the electrode arrangement 108 to the signal generation module 159. For example, the CPU 154 can forward information obtained from the external charger 101 via the coil 105 and the telemetry module 155.

The signal generation module 159 provides control signals to an output module 161 to produce therapy signals. In an embodiment, the control signals are based at least in part on the timing signals received from the CPU 154. The control signals also can be based on the electrode configuration information received from the CPU 154. The output module 161 produces the therapy signals based on the control signals received from the signal generation module 159. In an embodiment, the output module 161 produces the therapy signals by amplifying the control signals. The output module 161 then forwards the therapy signals to the lead arrangement 108.

In an embodiment, the signal generation module 159 receives power via a first power regulator 156. The power regulator 156 regulates the voltage of the power to a predetermined voltage appropriate for driving the signal generation module 159. For example, the power regulator 156 can regulate the voltage in a range of 1-20 volts.

In an embodiment, the output module 161 receives power via a second power regulator 160. The second power regulator 160 may regulate the voltage of the power in response to instructions from the CPU 154 to achieve specified constant voltage levels. The second power regulator 160 also may provide the voltage necessary to deliver constant current to the output module 161.

The output module 161 can measure the voltage of the therapy signals being outputted to the lead arrangement 108 and reports the measured voltage to the CPU 154. A capacitive divider 162 may be provided to scale the voltage measurement to a level compatible with the CPU 154. In another embodiment, the output module 161 can measure the impedance of the lead arrangement 108 to determine whether the electrodes 106, 106a are in contact with tissue. This impedance measurement also may be reported to the CPU 154. Impedance values of the leads are expected to be about 2000 to 10 megOhms based in part on the chiral vector, diameter or doping of the CNT coating the electrode or based on the composition of the polymer coating. In embodiments, impedance checks are conducted regularly throughout a treatment period to determine the integrity of the limited conductivity of the electrode. Loss of the limited conductivity of the electrode can result in a larger current leakage across the nerve resulting in nerve damage.

Another embodiment of a circuit is shown in Figure 3B. The therapy algorithm is divided into a number of very small time segments and the

corresponding voltage or current value of that therapy waveform segment is stored into a Field Programmable Gate Array(204). The therapy algorithm voltage or current values may be absolute values or changes relative to the previous voltage or current values. There is an option to retrieve alternate waveforms from an EEPROM (203). The clock oscillator (201) determines the time between successive therapy waveform segments and provides various clock signals for other circuits. The charge pump(205) provides the necessary voltage levels from the battery voltage for operating the circuits, the HV generator (207) and a current source (208)provide the applicable voltage and current levels for the therapy waveform which may be programmable by the user. Various voltage monitors (202), regulators and impedance detectors(206) measure and control the correct operation of the circuits. Some of the functionality is optional such as the memory(203) and telemetry blocks(155).

In addition, the power consumption needs of the neuroregulator 104 can change over time due to differences in activity. For example, the neuroregulator 104 will require less power to transmit data to the external charger 101 or to generate therapy signals than it will need to recharge the internal battery 151.

b. Electrodes

Electrodes, modified electrodes, electrical connections, and electrode CNT and/or polymer coatings impart beneficial features including electrodes and electrode coated with CNTs that are electrically stable over time following implantation in excitable tissue, relatively non-biodegradable yet biocompatible, have high electrical impedance, and limited conductivity. Electrodes coated with CNTs and/or polymer coatings are designed in order to provide sufficient capacitance to create an electrostatic field. As described herein, the CNT and/or polymer coating on the electrode increases the electrode's impedance, thereby preventing the leakage of current between the electrodes, resulting in the generation of a capacitive electrostatic field around the excitable tissue. In embodiments, the polymers have limited conductivity. In embodiments, the electrodes are employed in blocking nerve activity upon application of a selected constant voltage or constant current to the targeted nerve with little or no tissue damage. Yet in other

embodiments, the electrodes are employed in stimulating nerve activity upon application of a selected constant voltage or a constant current to the targeted nerve.

Impedance is related to the dielectric and resistivity (inverse of conductivity) of a coating through the following: impedance (z) is represented by a vector with capacitive reactance as the x-axis and resistance as the y-axis (FIG 5C). The magnitude of the impedance vector (which this application refers to as simply

"impedance") is the square root of resistance squared plus the capacitive reactance squared. The capacitive reactance = l/(2 fc), where f=frequency and c = capacitance. Capacitance = 8 _r 8o*A/d, where 8 _r = dielectric , ε ₀ = electric constant,* = multiplication, A = the area of the electrodes, and d = the distance between electrodes. Resistance = (resistivity)* (electrode thickness/electrode area).

Resistivity is related to impedance as follows:

Where R is the electrical resistance of a uniform specimen of the material (measured in Ohms, Ω), t is the length of the piece of material (measured in meters, m), and A is the cross sectional area of the specimen (measured in square meters m ² ).

Conductivity is the inverse of resistivity. The higher the resistivity the lower the conductivity.

In order to achieve a desired impedance with a given electrode surface area, electrode separation and coating thickness, the dielectric and/or resistivity (inverse of conductivity) of the electrode coating can be varied. The dielectric can range from about 2-100,000 and the resistivity is greater than 1 Ohm*cm, and in some embodiments, ranges from about 1 Ohm*cm to lxlO ¹⁴ Ohm*cm. For example with 2 electrodes, each with an area of 5 mm ² , a separation of 2 mm and a coating thickness of 50 μιη; a dielectric of 24 and a resistivity of 10 Ohm*cm would give an impedance (at 5000 Hz) of about 60,000 Ohms. Different combinations of dielectrics and resistivities of a coating could be used to achieve a desired impedance. For example, with the same electrode configuration as above, a dielectric of 1000 and a resistivity of 600,000 Ohm*cm would also yield an impedance of about 60,000 Ohms. To achieve a desired dielectric and resistivity different electrode coatings could be used, for example carbon nanotubes and/or limited conductive polymers.

In embodiments, the amount of charge per pulse delivered to a target neural tissue to result in at least a partial downregulation or upregulation of nerve activity can be determined by the impedance of the coated electrode, the size of the electrode, the distance of the electrodes from one another. For example, for two high impedance coated electrodes with negligible field sustaining current, the current fills the capacitance of the nerve electrode interface. For 2 electrodes, each with an area of 5 mm ² ' and a separation of 2 mm, the capacitance would = 8 _r 8o*A/d =

(8.854x l0 ^"12 F m ^_1 )*3*(5 mm 12 mm) = 66 picoFarad. Since capacitance is defined as charge (in coulombs (C)) divided by electric potential (in volts (V)), then charge = voltage*capacitance. At a selected voltage of 8 volts, the charge/pulse = (8 V)*(66 pF) = 0.53 nC to charge the electrode to nerve capacitance. This is a 1,600 fold decrease in charge/pulse to induce a conduction block than is necessary under the same conditions using a low impedance electrode with an impedance of 1000 Ohms or less.

In embodiments, one or more electrodes are coated with carbon nanotubes having an impedance of at least 2000 Ohms. Carbon nanotubes are three

dimensional structures created by wrapping a carbon graphene sheet into a cylinder. The graphene sheet comprises benzene hexagonal rings (Figure 6). Based on the wrapping of the graphene sheet a CNT falls into three categories: armchair, zigzag, and chiral, as described by its chiral vector with integers[ni, n _2] . If ni= n2, the CNT is termed armchair. If n ₂ =0 the CNT is termed zigzag, and all other configurations are considered chiral. In some embodiments, a CNT has about 10 atoms around its circumference and has diameters ranging from about 0.5 nM to 10 nM.

In some embodiments, CNTs comprise one graphene sheet, which is designated a single-walled CNT (hereinafter "SWCNT") and yet in other embodiments, CNTs are multiple layered graphene sheets, which are termed multi- walled CNTs (hereainfter "MWCNTs"). Both SWCNTs and MWCNTs can have a large length to diameter ratio of least about 1000.

It is within the scope of this disclosure to decrease the conductivity of CNTs and deposit them on a conductive electrode such as platinum. By altering its three- dimensional structure and/or by functionalizing the CNT, the conductivity of the CNTs can be fine-tuned to prevent leakage current while maintaining an electrostatic field around a targeted nerve.

The conductivity of CNTs depends on the three-dimensional structure and can range from the conductivity of copper to that of silicon. The structure of carbon nanotubes is defined by indices n,m. If n=m, then the structure is arm chair. Arm chair structures are metallic. If m=0, then the structure is zig zag, and zig zag structures have limited conductivity. Other structures are chiral. Chiral structures have limited conductivity. In the case of 2*ni + n ₂ that is not a multiple of 3, the CNT have limited conductivity. In embodiments, a carbon nanotube structure of at least zig zag and/or chiral structure is selected. In embodiments, carbon nanotube structures that are armchair are not selected. The diameter of the CNT also plays a role in its conductivity. In

embodiments, smaller diameter CNTs (0.5 to 2 nanometers) are less conductive (having a band gap of approximately 1.8 eV or more) than large diameter CNTs (greater than 2 nanometers) (having a band gap of approximately 0.18 eV or less).

In yet other embodiments, an extremely limited conductive CNT coating

(example greater than 1 megaOhm) could be functionalized with agents. In embodiments, carbon nanotubes are functionalized with fluorine. In embodiments, fluorinated single wall nanotubes have a resistance of about 40,000 ohms, whether or not, a voltage is applied.

In other embodiments, carbon nanotubes can be added to insulative polymers at an amount below the percolation threshold to form a composite. The percolation threshold is the amount of carbon nanotubes in a composite that results in an increase in conductivity. The amount of carbon nanotubes added to the polymer is such that the impedance or resistivity of the polymer is substantially maintained. In embodiments, the polymer is a polystyrene, poly epoxy, poly vinyl acetate, polyaniline, poly ethylene terephthalate, polycarbonate, poly methyl methacrylate, and polypropylene. In embodiments, the resistivity is at least 1 Ohm/cm or greater. Methods of forming composites and determining percolation thresholds are known in the art as described in, for example, Du et al, Macromolecules 2004 37:9048.

In other embodiments, carbon nanotubes are placed on a surface, preferable a conductive surface. In embodiments, the carbon nanotube layer is covered all or in part with a high impedance polymeric coating. In embodiments, the high impedance coating is placed around the edge of the electrode.

In embodiments, the CNT coated electrodes have an impedance of at least about 2000 Ohms or greater, at least about 10,000 Ohms or greater, at least about 60,000 ohms or greater, or at least about 10,000 to 10 megaOhms. The electrode or electrode coating can allow for some field sustaining current and still provide for nerve conduction block or stimulation without creating tissue damage. In

embodiments, such field sustaining current is about 400 nC/pulse or less. In embodiments, an electrode or electrode coated with CNTs is selected that minimizes field sustaining current.

In embodiments, the carbon nanotubes are deposited as a film or grown on a surface. In embodiments, the carbon nanotube layer is formed layer by layer to form a coating of certain thickness. In embodiments, carbon vapor deposition on a supported catalyst provides a limited conductive layer having diminished

conductance of about 100 kOhm to 1 MegaOhm. Such methods are known to those if skill in the art as described in Dai, Acc. Chem.Res. 2002, 35: 1035.

In embodiments, only a portion of the nanotube layer is coated with a polymer. Cyclic repetitions of applications of polymers with a carbon nanotube layer provide the carbon nanotube layer with a protective coating to minimize release of the carbon nanotube layer. In embodiments, the polymers are oppositely charged polyelectrolytes. In other embodiments, the polymers are biological polymers including laminin, collagen, poly lysine, polylysine conjugated laminin, fibronectin. Other surface coatings combined with a carbon nanotube layer include polyethylene glycol, mannitol, and oligoethylene glycol. In embodiments, the polymers are low conductive polymers such as, but not limited to, silicone, polyvinyl alcohol (PVA) or polyethylene oxide (PEO).

In embodiments, a carbon nanotube coating is treated with a substance to remove impurities. Such a substance includes acid washing, or washing with a chelator to remove metal impurities.

In other embodiments, the coating has topographical features. In

embodiments, the topological feature is roughness. In embodiments, the roughness comprises about20-70 nanometers. Another embodiments, involves a grooved topology. In embodiments, grooves are at least lOOnm wide and have a pitch of at least of 400 nm. In other embodiments, the width is about 100 to about 400nm. In other embodiments, the pitch is about 400 to 800 nm.

In embodiments, an electrode coating can have regions with different impedance values. In embodiments, a region has a carbon nanotube layer without any polymer coating. In embodiments, about 50% or less of the carbon nanotube layer is coated with a polymer coating having a different impedance value. In other embodiments, only a portion of the electrode is covered with a carbon nanotube layer.

In other embodiments, an electrode is coated with a low conducting polymer. Polymers can include, but are not limited to, a conjugated system that is doped or non-doped to achieve a desired resistivity. Examples of conjugated polymers include, but are not limited to: polyfluorenes, polyphenylenes, polypyrenes, polyazulenes, polynaphthalenes, polyacetylenes and poly(p-phenylene vinylene).

Polymers can comprise polyacetylene, polypyrrole, polyaniline and their copolymers, polythiophene, poly(3-alkylthiophene), polyphenylenesulphide, polyphenylene-vinylene, polythienylene-vinylene, polyphenylene, polyisothi- anaphthene, polyazulene, polyfuran, polyaniline, poly(3,4-ethylenedioxythiophene) or poly(3,4-ethylenedioxythiophene):polystyrene sulfonate. Non-conjugated polymers, such as l,4-poly(butadiene), could be doped to make a low conductive polymer. Polymers can comprise any class of ionomers.

In embodiments, a low conductive polymer will be coated onto conductive leads. An example includes mixing a conductive ionomer mixture such as poly(3,4- ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) with a nonconductive polymer such as polyvinyl alcohol (PVA) or polyethylene oxide (PEO). Changing the weight fraction of PEDOT:PSS in the nonconductive polymer host (PVA or PEO) will gradually change the impedance of the polymer mix. Coating thicknesses can range from about 50 microns to 250 microns and impedance will change linearly with the thickness of the coating. In embodiments, modulating conductivity by doping of polymers such as, but not limited to, polypyrrole, polythiophene, polyaniline, and polyacetylene can be used to create a low conducting polymer.

In other embodiments, materials such as, but not limited to, silicon could be doped to achieve a desired resistivity varying from 1 ohm*cm to about 10 ⁴

Ohm* cm.

In other embodiments, electrode surface area and electrode separation can be modified to change the impedance of the system. Decreasing electrode surface area will increase impedance.

In embodiments, an electrode has an impedance of at least about 2000 to 10 megOhms, 2000 to 6 megOhms, 2000 to 1 megOhm, 2000 to 175,000 Ohms, 2000 to 100000 Ohms, 2000 to 60,000 Ohms, or 2000 to 20,000 Ohms. In other embodiments, an electrode has an impedance of at least about 10000 to

lOmegOhms, 10000 to 6 megOhms, 10000 to 1 megOhm, 10000 to 175,000 Ohms, 10000 to 100000 Ohms, 10000 to 60,000 ohms, or 10000 to 20,000 Ohms. In yet a further embodiment, an electrode has an impedance of at least about 60,000 to 10 megOhms, 60,000 to 6 megOhms, 60,000 to 1 megOhm, 60,000 to 175,000 Ohms, or 60,000 to 100000 Ohms.

In embodiments, the field sustaining current is about 400 nC/pulse or less, 40 nC/pulse or less, 15 nC/pulse or less, 10 nC/pulse or less, 5 nC/pulse or less, 1 nC/pulse or less, or 0.5 nC/pulse or less. In embodiments, the CNT and/or polymer coated electrode has a resistivity of at least 1 Ohms*cm. In embodiments, the electrodes have a resistivity of about 10 ² to 10 ²⁴ , 10 ² to 10 ²⁰ , 10 ² to 10 ¹⁵ , or 10 ² to 10 ¹⁰ ohms-*cm. Resistivity's of materials are known to those of skill in the art and as identified, for example, in the Handbook of Polymers. For example, silicone rubber has a resistivity of 4 x 10 ¹⁰ . Polyurethane has a resistivity of 10 ¹⁴ . Teflon has a resistivity of 10 ²⁰ . High density polyethylene has a resistivity of 10 ¹⁷ .

The present disclosure provides limited conductive CNT and/or polymer coatings which can be deposited on a substrate, preferably, commonly used conductive substrate materials such as platinum, iridium, indium, tin oxide, and tungsten. According to the disclosure, there is provided an implantable electrode having a limited conductive coating comprising CNTs and/or polymer coating. In embodiments, the coating is present in one or more coating layers on a surface thereof, the coating layer or at least one of the coating layers being for contact with body tissue when the electrode is implanted and each coating layer being an electrically non-conductive layer.

Limited conductive coatings can be deposited on the surface of an electrode, for example, by arc discharge, laser ablation or chemical vapor deposition. A CNT coating is at least about 1 to 1000, 1 to 100, or 1 to 10 microns thick. Increasing thickness will decrease conduction. . In some embodiments, the electrodes and leads have a variety of configurations including bipolar, tripolar and the like. In embodiments, at least two electrodes are found on a single lead. In other

embodiments, each lead has one electrode, and multiple leads are employed.

In embodiments, the electrodes are positioned on a target nerve or neural tissue so that an electric field can be created between them. The surface area of the electrode is selected based on the impedance value and the charge per pulse to be delivered to the nerve in order to provide downregulation or upregulation of nerve activity. In embodiments, the total charge per pulse delivered to the nerve electrode interface can be modified depending on the surface area of the electrode and the distance that the electrodes are apart. In certain embodiments, the surface area of the electrode is about 0.01 to 20 mm ² . In embodiments, the distance between the electrodes is about 0.1 mm to 20 mm.

The high impedance electrodes can be placed in or near any excitable tissue.

In embodiments, the device and electrodes described herein can be placed on or near the vagus nerve, cranial nerves, celiac nerve, celiac plexus, renal nerve, splanchnic nerve, glossopharyngeal nerve, facial nerve, baroreceptors, sacral nerves, pudendal nerve, renal plexus, dorsal roots, dorsal column of the spinal cord, subthalamic nucleus, globus pallidus, thalamus, motor cortex or Brodmann Area 25. In embodiments, a target nerve includes the vagus nerve, the splanchnic nerve or the renal nerve.

In embodiments, the electrodes are placed on a vagus nerve, preferably below the diaphragm. The posterior nerve PVN and the anterior AVN are generally on diametrically opposite sides of the esophagus E just below the patient's diaphragm. A first tip electrode 212 of a lead arrangement 108 (FIG. 1) is placed on the anterior vagus nerve AVN. A second electrode 212a of the lead arrangement 108 is placed on the posterior vagus nerve PVN. The electrodes 212, 212a are connected by leads 106, 106a to a neuroregulator 104 (FIG. 1).

At the time of placement of the leads 106, 106a, it may be advantageous for the tip electrodes 212, 212a to be individually energized with a stimulation signal selected to impart a neural impulse to cause a detectable physiological response (e.g., the generation of antropyloric waves). The absence of a physiological response may indicate the absence of an overlying relation of the tested electrode 212, 212a to a vagus nerve PVN, AVN. Conversely, the presence of a physiological response may indicate an overlying relation (e.g., correct placement) of the tested electrode 212, 212a to a vagus nerve. After determining the leads 106, 106a create a physiologic response, the electrodes 212, 212a can be attached to the nerves PVN, AVN. The therapies as described herein may be employed by using blocking electrodes or stimulation electrodes or both in order to down-regulate and/or up- regulate the target nerve.

FIG. 7 illustrates an example embodiment of an electrode partially coated with high impedance CNTs. For example, as shown in FIG. 7, the electrode surface 300 comprises a first portion 302 and a second portion 304. In this example, the first portion is not coated with CNTs, but is coated with a low conducting polymer. The second portion 304, however, is coated with CNTs, thereby allowing the generating of an electrostatic field upon application of a voltage signal as described herein.

As described herein, coating the electrodes with CNTs and/or low

conducting polymer increases the impedance of the electrode, thereby minimizing current leakage and inducing an electrostatic field between the two electrodes applied to a target nerve. In some embodiments, however, it is beneficial to only partially coat the electrode, thereby allowing the electrode to sense signals from the nerve to which it is applied.

FIG. 8 illustrates a method 400 for applying a treatment to a nerve using two or more electrodes coated with high impedance CNTs and/or low conducting polymers. The method 400, performed by the implantable device, such as the neuroregulator 104 begins at step 402 in which the implantable device wirelessly receives therapy instructions from the external device, such as the external charger 101. As described herein, such therapy instructions include, but are not limited to the pulse-width, amplitude, and frequency of the desired therapy signal. In some embodiments, however, the therapy instructions simply include a target goal or an identification of a particular therapy. Next, flow proceeds to step 404 in which the implantable device generates therapy signals based at least in part on the therapy instructions. As described herein, therapy signals may be saved within memory of the implantable device. Accordingly, the implantable device determines, based on instructions received from the external device, the specific therapy signals for delivery to the electrodes. Next, flow proceeds to step 406 in which the implantable device applies a voltage, based on the therapy signal generated in step 404, to the first and second electrodes. As described herein, the high impedance CNT and/or polymer coating minimizes the current leakage through the electrodes. Accordingly, the electrodes are charged in response to an application of the voltage signal, thereby ultimately causing the generation of an electrical field around the target nerve upon reaching a charged state. The electrical field generated around the target nerve modulates a desired activity, such as an upregulation or a downregulation, of the target nerve. As described with reference to FIG. 6, in some embodiments, the electrodes are only partially coated with CNTs. In such applications, the therapy voltage signal is only applied to the CNT coated portion of the first and second electrodes.

c. Electrical signal parameters and delivered charge

An electrical signal can be generated with a constant but selectable voltage, constant but selectable current in the devices described herein. While not meant to limit the scope of the disclosure, it is believed using CNT and/or polymer coated electrodes with high impedance results in nerve conduction block with less delivered charge than that of a low impedance electrode. In embodiments, the amount of charge per pulse delivered to a target neural tissue to result in at least a partial downregulation or upregulation of nerve activity can be determined by the impedance of the coated electrode, the size of the electrode, the distance of the electrodes from one another. A constant voltage or current at a selected frequency is then selected using the following equation:

Capacitance = 8 _r 8o*A/d (1)

where ε _Γ = relative static permittivity, ε ₀ = electric constant,* = multiplication, A = the area of the electrodes, and d = the distance between electrodes. Pulse width may be adjusted as therapy continues to increase efficacy of the therapy.

For example, for two high impedance coated electrodes with negligible field sustaining current, the current fills the capacitance of the nerve electrode interface. For 2 electrodes, each with an area of 5 mm ² ' and a separation of 2 mm, the capacitance would = ε _Γ ε ₀ *ΑΛ1 = (8.854 l0 ^~12 F m ^_1 )*3*(5 mm ² /2 mm) = 66 picoFarad. Since capacitance is defined as charge (in coulombs (C)) divided by electric potential (in volts (V)), then charge = voltage* capacitance. At a selected voltage of 8 volts, the charge/pulse = (8 V)*(66 pF) = 0.53 nC to charge the electrode to nerve capacitance. This is a 1,600 fold decrease in charge/pulse to induce a conduction block than is necessary under the same conditions using a low impedance electrode with an impedance of 1000 Ohms or less.

Electrical signal parameters are designed in order to provide for a certain amount of delivered charge/pulse using a high impedance CNT and/or polymer coated electrode as compared to a typical low impedance electrode. In embodiments, the impedance of the CNT and/or low conductive polymer coated electrode, the size of the electrode, and the distance of the electrode vary between applications. As discussed herein, in embodiments, impedance can vary from about 2000 Ohms to 10 megOhms. In embodiments, the size of the high impedance coated electrode can vary from about 0.1 to about 20 mm ² . In embodiments, the distance between the high impedance coated electrodes can range from about 0.1 to about 20 mm.

In embodiments, frequencies are selected that provide for upregulating and/ or down regulating signal. For a downregulating or blocking signal, frequencies are selected of 200 Hz or greater. For example, a frequency of at least about 200 to

10,000 Hz, 200 to 5000 Hz, 200 to 2500 Hz, 200 to 1000Hz, 250 to 10,000 Hz, 250 to 5000 Hz, 250 to 2500 Hz, 250 to 1000 Hz, 500 to 10,000 Hz, 500 to 5000 Hz, 500 to 2500 Hz, or 500 to 1000 Hz. For an upregulating signal, frequencies are selected at less than 200 Hz. For example, about 1 to 195 Hz, 1 to 150 Hz, 1 to 100 Hz, 1 to 75 Hz, 1 to 50 Hz, or 1 to 25 Hz.

If a high frequency conduction blocking signal (e.g. 200 Hz or greater) using alternating current is applied to a target nerve using a constant but selectable voltage, the voltage can be selected from about 1 volt to about 50 volts, about 1 volt to 25 volts, about 1 volt to about 15 volts, or about 1 volt to about 10 volts, or about 3 to 8 volts. In embodiments, the voltage is about 8 to 10 volts in order to minimize power requirements of the battery.

If a high frequency conduction blocking signal(e.g. 200 Hz or greater) using alternating current is applied to a target nerve using constant current, the current can range from about 0.1 to 15000 μΑιηρ, 0.1 to 1 μΑιηρ, about 1 to 10 μΑιηρ, about 10 to 300 μΑιηρ, about 100 to 1000 μΑιηρ, about 1000 to 15000 μΑιηρ, or about 3000 to 8000 μΑιηρ.

If a low frequency upregulating signal (e.g. less than 200 Hz) using alternating current is applied to a target nerve using a constant but selectable voltage, the voltage can be selected from about 1 volt to about 50 volts, about 1 volt to 25 volts, about 1 volt to about 15 volts, or about 1 volt to about 10 volts. In embodiments, the voltage is about 8 to 10 volts in order to minimize power requirements of the battery.

If a low frequency upregulating signal (e.g. less than 200 Hz) using alternating current is applied to a target nerve using a constant but selectable current, the current can range from about 0.1 to 15000 μΑιηρ, 0.1 to 1 μΑιηρ, about 1 to 10 μΑιηρ, about 10 to 300 μΑιηρ, about 100 to 1000 μΑιηρ, or about 1000 to 15000 μΑιηρ.

In embodiments, the constant voltage or constant current can be generated by an alternating current or direct current source. In embodiments, the constant voltage or constant current can be generated using radiofrequency such that the device does not require a battery as described above,

d. Duty Cycle

In embodiments, the duty cycle can be varied. A duty cycle is defined as the percentage of time current or voltage is delivered in one cycle. In embodiments, a high frequency electrical signal is employed to create a nerve conduction block. In embodiments, the frequency of the signal is 200 Hz or greater, about 200 Hz to about 50,000 Hz, about 200 to 10,000 Hz, about 200 to 5000 Hz, about 200 to 2500 Hz, about 200 to 1000 Hz, about 200 to 500 Hz, about 300 Hz to about 50,000 Hz, about 300 to 10,000 Hz, about 300 to 5000 Hz, about 300 to 2500 Hz, about 300 to 1000 Hz, or about 300 to 500 Hz. In embodiments, the external component is configured to allow a user to select any one of a number of frequencies.

The pulse width of a high frequency electrical signal of the same frequency can be varied to vary the duty cycle from about 1 to 100%. For example, a high frequency signal of 5000 Hz has a 100% duty cycle when the pulse width is 100 microseconds. If the frequency is maintained at 5000 Hz, the duty cycle can be decreased by decreasing the pulse width. For example, a pulse width of 10 microseconds is a 10% duty cycle. It has been shown that pulse widths of a high frequency electrical signal that are less than 100% duty cycle are sufficient to create a nerve conduction block using the limited conductivity electrodes described herein. In embodiments, an external component is configured to provide a selection of duty cycles so that the % of blocking of nerve activity can be adjusted based on efficacy for treatment of the disorder and comfort of the patient.

For application of a low frequency electrical signal in order to upregulate activity on a target neural tissue, the frequency selected is about 200 Hz or less about 0.01 to 150 Hz, about 0.01 to 100 Hz, or about 0.01 to 50 Hz. For example, for a biphasic electrical signal delivered at 50 Hz, a pulse width of 10 millisecond (ms) is a 100% duty cycle. Typical pulse widths range from about 0.06-0.8 ms, about 0.06-1 ms or about 0.4-10 ms.

In embodiments, a therapy cycle can include a duty cycle that starts at 1% and increases to 100% during the on time. During the on time, in the case of a 5000 Hz signal, the pulse width of the electrical signal can be increased incrementally from about 1 microsecond up to 100 microseconds. In other embodiments, the duty cycle begins at 100% and decreases to 1% during an on time. During the on time, in the case of a 5000 Hz signal, the pulse width of the electrical signal can be decreased incrementally from about 100 microseconds to 1 microsecond.

Variation of the pulse width of the electrical signal using the systems described herein provides a method to vary the % of blocking of the nerve activity. For example, a 10 microsecond pulse provides about 10% or less blocking of nerve activity. As the pulse width increases up to 100 microseconds, the blocking activity increases to about 40% or greater. If the original pulse width selected does not provide efficacious therapy for the disorder pulse width may be increased in order to increase the % of nerve activity blocked.

B. System Software

The external charger 101 and the neuroregulator 104 contain software to permit use of the therapy system 100 in a variety of treatment schedules, operational modes, system monitoring and interfaces as will be described herein.

1. Treatment Schedule

To initiate the treatment regimen, the clinician downloads a treatment specification and a therapy schedule from an external computer 107 to the external charger 101. In general, the treatment specification indicates configuration values for the neuroregulator 104. For example, in the case of vagal nerve treatment for obesity, the treatment specification may define the amplitude, fixed but selectable voltage or current, frequency, impedance values of the electrode, and pulse width for the electrical signals emitted by the implanted neuroregulator 104. In another embodiment, "ramp up" time (i.e., the time period during which the electrical signals builds up to a target amplitude) and "ramp down" time (i.e., the time period during which the signals decrease from the target amplitude to about zero) can be specified.

In general, the therapy schedule indicates an episode start time and an episode duration for at least one day of the week. An episode refers to the administration of therapy over a discrete period of time. Preferably, the clinician programs an episode start time and duration for each day of the week. In an embodiment, multiple episodes can be scheduled within a single day. Therapy also can be withheld for one or more days at the determination of the clinician.

During a therapy episode, the neuroregulator 104 completes one or more treatment cycles in which the neuroregulator 104 sequences between an "on" state and an "off state. For the purposes of this disclosure, a treatment cycle includes a time period during which the neuroregulator 104 continuously emits treatment (i.e., the "on" state) and a time period during which the neuroregulator 104 does not emit treatment (i.e., the "off state). Typically, each therapy episode includes multiple treatment cycles. The clinician can program the duration of each treatment cycle

(e.g., via the clinician computer 107).

When configured in the "on" state, the neuroregulator 104 continuously applies treatment (e.g., emits an electrical signal). The neuroregulator 104 is cycled to an "off state, in which no signal is emitted by the neuroregulator 104, at intermittent periods to mitigate the chances of triggering a compensatory mechanism by the body. For example, if a continuous signal is applied to a patient's nerve for a sufficient duration, the patient's digestive system eventually can learn to operate autonomously.

The daily schedule includes a timeline indicating the times during the day when the treatment is scheduled to be applied to a patient. Duty cycle lines (dashed lines) extend along the time periods during which treatment is scheduled. For example, a first episode is scheduled between 8 AM and 9 AM. In certain embodiments, the treatment schedules address other details as well. For example, the daily schedule indicates details of the waveform (e.g., ramp-up/ramp-down characteristics) and details of the treatment cycles.

2. Electrode Impedance Measurement

Embodiments of the therapy system 100 have the ability to independently measure and record electrode impedance values. Electrode impedance values outside a predefined range may indicate problems or malfunctions within the therapy system 100. These embodiments of the therapy system 100 allow the physician to measure electrode impedance on-demand. The therapy system 100 also enables the physician to periodically measure impedance without initiating a blocking therapy setting. Generally, impedance is measured and stored separately for each channel of each electrode configuration. These measurements may be used to establish a nominal impedance value for each patient by calculating a moving average. In embodiments, impedance values range from about 2000 Ohms to 10 megaOhms. Any decrease in impedance value could indicate that the limited conductivity of the electrode is decreasing due to release or wear of any coating.

3. External Computer Interface

Programmer software, with which the physician can program treatment configurations and schedules, resides on and is compatible with an external computing device 107 (FIG. 1) that communicates with the external charger 101. In general, application software for the computing device 107 is capable of generating treatment programs stored in a commonly accepted data file format upon demand.

The programming interface of the computing device 107 is designed to enable the physician to interact with the components of the therapy system 100. For example, the programming interface can enable the physician to modify the operational modes (e.g., training mode, treatment mode) of the external charger 101. The programming interface also can facilitate downloading treatment parameters to the external charger 101. The programming interface enables the physician to alter the treatment parameters of the neuroregulator 104, and to schedule treatment episodes via the external charger 101.

The programming interface also enables the physician to conduct intraoperative testing amongst the components of the therapy system 100. For example, the physician can initiate an electrode impedance test via the programming interface. The physician also can program temporary treatment settings for special physiologic testing. The programming interface also can facilitate conducting diagnostic stimulation at follow-up visits between the patient and the physician.

The programming interface of the computing device 107 also enables the physician to access patient data (e.g., treatments delivered and noted physiological effects of the treatment). For example, the programming interface can enable the physician to access and analyze patient data recorded by the therapy system 100 (e.g., stored in the memory 152 of the neuroregulator 104 and/or the memory 181 of the external charger 101). The physician also can upload the patient data to the external computing device 107 for storage and analysis.

The programming interface also can enable the physician to view system operation information such as non-compliant conditions, system faults, and other operational information (e.g., electrode impedance) of the therapy system 100. This operational data also can be uploaded to the external computing device 107 for storage and analysis.

4. Programs

One or more therapy programs can be stored in the memory of the external computer 107. The therapy programs can include a range of predetermined parameters and therapy delivery schedules. For example, each therapy program can specify a selectable current or voltage, a frequency, duty cycle, a charge per pulse, a pulse width, ramp-up rates, ramp-down rates, and an on-off cycle period. In an embodiment, one or more of these parameters can be individually and separately programmed. For example, a constant voltage range of about 1 to 20 volts may be selectable with a default value at 8 or 14 volts. The current can range from about 0.1 to 15000 μΑιηρ, 0.1 to 1 μΑιηρ, about 1 to 10 μΑιηρ, about 10 to 300 μΑιηρ, about

100 to 1000 μΑιηρ, about 1000 to 15000 μΑιηρ with a default value set at 1000 μΑιηρ, or about 3000 to 8000 μΑιηρ. In another example, frequencies can be selected from 200 Hz to 10,000 Hz, with a default value set at 5000 Hz. In yet another example, the pulse width can be selected from 1 to 100 microseconds, with a default value of 90 or 10 microseconds.

In embodiments, a therapy delivery schedule can also be selectable. In embodiments, a range of therapy hours per day are selectable from 1 to 24 hours. In embodiments, the default value can be 6, 9, or 12 hours. In addition, the start time or end time of the therapy schedule is selectable. For example, in the case of hypertension, a start time can begin as early as 4 or 5 am. In another example, a start time can be in the late afternoon or evening in order to accommodate shift work. In that case, a start time can range from 4 pm to about 9pm.

In use, the physician may select any one of these therapy programs and transmit the selected therapy program to the implanted neuroregulator 104 (e.g., via the external charger 101) for storage in the memory of the neuroregulator 104. The stored therapy program then can control the parameters of the therapy signal delivered to the patient via the neuroregulator 104.

Typically, the default parameter settings of the programs are set at the factory, prior to shipment. However, each of these parameters can be adjusted over a certain range, by the physician, using the computer 100 to produce selectable, customized, therapy programs. Using these selectable, customized therapy programs, the physician can manage the patient's care in an appropriate manner.

For example, when patients require more varied therapies, the neuroregulator 104 can store a therapy program including one or more combinations of multiple therapy modes sequenced throughout the day.

C. External Charger

An embodiment of the external charger 101 can change the amplification level of the transmission signal (e.g., of power and/or data) to facilitate effective transmission at different distances between, and for different relative orientations of, the coils 102, 105. If the level of power received from the external charger 101 varies, or if the power needs of the neuroregulator 104 change, then the external charger 101 can adjust the power level of the transmitted signal dynamically to meet the desired target level for the implanted neuroregulator 104.

Waveforms delivered to the nerve to at least partially block nerve activity are designed and selected to minimize power consumption. Minimizing power consumption of the therapy allows for the use of a smaller battery and/or less recharging sessions.

A block diagram view of an example external charger 101 is shown in FIG. 4. The example external charger 101 may cooperate with any of the neuroregulators 104, 104' discussed above to provide therapy to a patient. The external charger 101 is configured to transmit to the neuroregulator 104 (e.g., via an RF link) desired therapy parameters and treatment schedules and to receive data (e.g., patient data) from the neuroregulator 104. The external charger 101 also is configured to transmit energy to the neuroregulator 104 to power the generation of therapy signals and/or to recharge an internal battery 151 of the neuroregulator 104. The external charger 101 also can communicate with an external computer 107.

In general, the external charger 101 includes power and communications circuitry 170. The power and communications circuitry 170 is configured to accept input from multiple sources, to process the input at a central processing unit (CPU) 200, and to output data and/or energy (e.g., via coil 102, socket 174, or display 172). It will be appreciated that it is well within the skill of one of ordinary skill in the art (having the benefit of the teachings of the present invention) to create such circuit components with such function.

For example, the circuit power and communications circuit 170 can be electrically connected to the external coil 102 for inductive electrical coupling to the coil 105 of the neuroregulator 104. The power and communications circuit 170 also can be coupled to interface components enabling input from the patient or an external computing device (e.g., a personal computer, a laptop, a personal digital assistant, etc.) 107. For example, the external charger 101 can communicate with the computing device 107 via an electrically isolated Serial port.

The external charger 101 also includes a memory or data storage module 181 in which data received from the neuroregulator 104 (e.g., via coil 102 and socket input 176), the external computer 107 (e.g., via socket input 174), and/or the patient (e.g. via select input 178) can be stored. For example, the memory 181 can store one or more parameters, therapy programs and/or therapy schedules provided from the external computer 107. The memory 181 also can store software to operate the external charger 101 (e.g., to connect to the external computer 107, to program external operating parameters, to transmit data/energy to the neuroregulator 104, and/or to upgrades the operations of the CPU 200). Alternatively, the external charger 101 can include firmware to provide these functions. The memory 181 also can store diagnostic information, e.g., software and hardware error conditions.

An external computer or programmer 107 may connect to the

communications circuit 170 through the first input 174. In an embodiment, the first input 174 is a port or socket into which a cable coupled to the external computer 107 can be plugged. In other embodiments, however, the first input 174 may include any connection mechanism capable of connecting the external computer 107 to the external charger 101. The external computer 107 provides an interface between the external charger 101 and a physician (e.g., or other medical professional) to enable the physician to program therapies into the external charger 101, to run diagnostic and system tests, and to retrieve data from the external charger 101.

The second input 176 permits the external charger 101 to couple selectively to one of either an external power source 180 or the external coil 102 (see FIG. 1). For example, the second input 176 can define a socket or port into which the power source 180 or external coil 102 can plug. In other embodiments, however, the second input 176 can be configured to couple to a cable or other coupling device via any desired connection mechanism. In one embodiment, the external charger 101 does not simultaneously connect to both the coil 102 and the external power source 180. Accordingly, in such an embodiment, the external power source 180 does not connect directly to the implanted neuroregulator 104.

The external power source 180 can provide power to the external charger 101 via the second input 176 when the external charger 101 is not coupled to the coil 102. In an embodiment, the external power source 180 enables the external charger 101 to process therapy programs and schedules. In another embodiment, the external power source 180 supplies power to enable the external charger 101 to communicate with the external computer 107 (see FIG. 1).

The external charger 101 optionally may include a battery, capacitor, or other storage device 182 (FIG. 4) enclosed within the external charger 101 that can supply power to the CPU 200 (e.g., when the external charger 101 is disconnected from the external power source 180). The power and communications circuit 170 can include a power regulator 192 configured to receive power from the battery 182, to regulate the voltage, and to direct the voltage to the CPU 200. In a preferred embodiment, the power regulator 192 sends a 2.5 volt signal to the CPU 200.

The battery 182 also can supply power to operate the external coil 102 when the coil 102 is coupled to the external charger 101. The battery 182 also can supply power to enable the external charger 101 to communicate with the external computer 107 when the external power source 180 is disconnected from the external charger 101. An indicator 190 may provide a visual or auditory indication of the remaining power in the battery 182 to the user.

In an embodiment, the battery 182 of the external charger 101 is

rechargeable. A decrease in charge per pulse of at least 2 to 80000 fold results in a significant energy savings that would allow for use of a smaller battery in a smaller device, or reduced charging of once per month or less. For example, the external power source 180 may couple to the external charger 101 to supply a voltage to the battery 182. In such an embodiment, the external charger 101 then can be disconnected from the external power source 180 and connected to the external coil 102 to transmit power and/or data to the neuroregulator 104.

In an alternative embodiment, the battery 180 is a replaceable, rechargeable battery, which is recharged external to the external charger 101 in its own recharging stand. In yet another embodiment, the battery 182 in the external charger 101 can be a replaceable, non-rechargeable battery.

In use, energy from the external power source 180 flows through the second input 176 to an energy transfer module 199 of the power and communications circuit 170. The energy transfer module 199 directs the energy either to the CPU 200 to power the internal processing of the external charger 101 or to the battery 182. In an embodiment, the energy transfer module 199 first directs the energy to a power regulator 194, which can regulate the voltage of the energy signal before sending the energy to the battery 182.

In some embodiments, the external coil 102 of the external charger 101 can supply energy from the battery 182 to the internal coil 105 of the neuroregulator 104 (e.g., to recharge the internal power source 151 (FIG. 3) of the neuroregulator 104). In such embodiments, the energy transfer module 199 receives power from the battery 182 via the power regulator 194. For example, the power regulator 194 can provide a sufficient voltage to activate the energy transfer module 199. The energy transfer module 199 also can receive instructions from the CPU 200 regarding when to obtain power from the battery 182 and/or when to forward power to the external coil 102. The energy transfer module 199 delivers the energy received from the battery 182 to the coil 102 of the external charger 101 in accordance with the instructions provided by the CPU 200. The energy is sent from the external coil 102 to the internal coil 105 of the neuroregulator 104 via RF signals or any other desired power transfer signal. In an embodiment, therapy delivery at the neuroregulator 104 is suspended and power is delivered from the external charger 101 during recharging of the internal power source 151.

In some embodiments, the external charger 101 controls when the internal battery 151 of the implanted neuroregulator 104 is recharged. In embodiments, the implanted neuroregulator 104 controls when the battery 151 is recharged. These details typically parallel the battery manufacturer's recommendations regarding how to charge the battery.

As noted above, in addition to power transmissions, the external coil 102 also can be configured to receive data from and to transmit programming instructions to the neuroregulator 104 (e.g., via an RF link). A data transfer module 196 may receive and transmit data and instructions between the CPU 200 and the internal coil 105. In an embodiment, the programming instructions include therapy schedules and parameter settings. Further examples of instructions and data transmitted between the external coil 102 and the implanted coil 105 are discussed in greater detail herein.

Example functions capable of selection by the user include device reset, interrogation of battery status, interrogation of coil position, and/or interrogation of electrode/tissue impedance. In other embodiments, a user also can select

measurement of tissue/electrode impedance and/or initiation of a stomach contraction test. Typically, the measurement and testing operations are performed when the patient is located in an operating room, doctor's office, or is otherwise surrounded by medical personnel.

In another embodiment, the user can select one or more parameters, programs and/or therapy schedules to submit to the memory 152 of the

neuroregulator 104. For example, the user can cycle through available parameters or programs by repeatedly pressing the selection button 178 on the external charger 101. The user can indicate the user's choice by, e.g., depressing the selector button

178 for a predetermined period of time or pressing the selector button 178 in quick succession within a predetermined period of time.

In use, in some embodiments, the external charger 101 may be configured into one of multiple modes of operation. Each mode of operation can enable the external charger 101 to perform different functions with different limitations. In an embodiment, the external charger 101 can be configured into five modes of operation: an Operating Room mode; a Programming mode; a Therapy Delivery mode; a Charging mode; and a Diagnostic mode.

D. Methods

In another aspect, the disclosure provides methods of using the system described herein. In embodiments, a method of treating a disorder in a subject comprises applying a CNT and/ or polymer coated electrode to a target nerve, wherein the coated electrode has an impedance of at least 2000 ohms and is operatively coupled to an implantable neuroregulator; applying a therapy cycle to the target nerve, wherein the therapy cycle comprises applying an electrical signal to the coated electrode intermittently, wherein the coated electrode signal is applied using a constant voltage or constant current and is selected to downregulate activity on the target nerve. In other embodiments the electrical signal is selected to upregulate activity on the nerve.

Methods of the disclosure can be applied to any excitable tissue. In embodiments, a nerve such as the vagus nerve, splanchnic nerve, celiac nerve, celiac plexus, renal nerve, cranial nerves, glossopharyngeal nerve, baroreceptors are targeted. In embodiments, the target nerve is the cardiac ganglia including at the sinoatrial node and ventricular vagal ganglia. Disorders for which modulation of nerve activity is desired are selected. Such disorders include obesity, diabetes, hypertension, inflammatory bowel disease, metabolic disorders, pancreatitis, cardiac disorders, and bulimia. Additionally, neurological disorders such as, but not limited to, chronic pain, movement disorders, seizures, refectory depression, obsessive compulsive disorder, and inconsistence may also benefit from therapies as described herein.

In embodiments, a method comprises applying a CNT and/ or polymer coated electrode to a target nerve, wherein the coated electrode has an impedance of at least 2000 ohms and is operatively coupled to an implantable neuroregulator; applying a therapy cycle to the target nerve, wherein the therapy cycle comprises applying an electrical signal to the coated electrode intermittently, wherein the coated electrode signal is applied using a constant voltage or constant current and is selected to upregulate activity on the target nerve. In embodiments, the target nerve is a cardiac vagal nerve including the sinoatrial node and the ventricular vagal ganglia. In embodiments, the upregulating electrode signal has a frequency of 200 Hz or less, 150 Hz or less, 100Hz or less, or 50 Hz or less. In embodiments, a current is selected to decrease side effects of stimulating the cardiac vagal nerves. Such side effects include increased heart rate, increased blood pressure, and vocal stimulation. In embodiments, the method includes application of the electrical signal at a current of about 3-8 mAmps.

In embodiments at least two coated electrodes are applied to a target nerve in order to generate an electrical field. The at least two electrodes can be present in a single or multiple leads. The surface of the electrode contacting the nerve is coated with CNTs and/or low conductive polymers to produce high impedance. Such electrodes can be obtained by applying one or more types of CNT coatings that have limited conductivity as described herein. In embodiments, the CNT coated electrodes have an impedance of at least 2000 ohms as described previously herein.

Application of a therapy cycle involves applying an electrical signal to the nerve via the CNT coated electrodes. In embodiments, an electrical signal is generated using constant voltage. A constant voltage can be selected and set by the physician ranging from 1 to 50 volts, 1 to 40 volts, 1 to 30 volts, 1 to 20 volts, or 1- 10 volts.

The current can range from about 0.1 to 15000 μΑπιρ, 0.1 to 1 μΑπιρ, about 1 to 10 μΑιηρ, about 10 to 300 μΑιηρ, about 100 to 1000 μΑιηρ, about 1000 to 15000 μΑιηρ or about 3000 to 8000 μΑιηρ.

The constant voltage may be set based on the selected pulse width. For a particular frequency, pulse width can be selected to include a duty cycle of about 1- 100%. For example, for an electrical signal of 5000Hz, a 100% duty cycle will have a pulse width of 100 microseconds. The pulse width can range from 10 to 100 microseconds. The pulse width may be varied during treatment in order to enhance the efficacy of the therapy cycle or in response to the comfort of the patient.

For downregulating activity of a nerve such as the vagus nerve, the frequencies include 200 Hz or greater, about 200 Hz to about 50,000 Hz, about 200 to 10,000 Hz, about 200 to 5000 Hz, about 200 to 2500 Hz, about 200 to 1000 Hz, about 200 to 500 Hz, about 300 Hz to about 50,000 Hz, about 300 to 10,000 Hz, about 300 to 5000 Hz, about 300 to 2500 Hz, about 300 to 1000 Hz, or about 300 to 500 Hz. For an upregulating signal, frequencies are selected at less than 200 Hz. For example, about 1 to 195 Hz, 1 to 150 Hz, 1 to 100 Hz, 1 to 75 Hz, 1 to 50 Hz, or 1 to 25 Hz.

In embodiments, a method of setting the parameters for a therapy cycle comprises selecting a frequency, followed by selecting one or more pulse widths, and then selecting a constant voltage or constant current based on the selected pulse widths. In embodiments, the physician programmer or the external component has a user interface that allow selection of each of these parameters.

One aspect of the present disclosure relates to a method of modulating taste for designing a therapy or for treating a gastrointestinal disorder or a condition associated with excess weight in a subject including at least one electrode configured to be implanted within a body of the patient and placed at a cranial nerve, the electrode also configured to apply therapy to the cranial nerve upon application of a therapy cycle to the electrode. The method including the steps of sensing food ingestion by measuring gastric distention, activity of a vagus nerve, activity of gustatory afferents and mastication; selecting a parameter for triggering a set of pulses applied at a selected frequency to a nerve; and applying electrical modulation of efferent gustatory signals to the nerve, wherein electrical modulation of the nerves alters taste perception to increase the amount of excess weight loss.

The present disclosure describes electrical signals that can be used to temporarily and reversibly modulate nerves carrying afferent gustatory information to alter, or block, taste perception. In one embodiment, electrically modulating transmission signals may be applied along the Chroda Tympani to induce dysgeusia and provide a therapy treatment for obesity. In another embodiment, electrically modulating transmission signals may be applied along the pharyngeal branches to induce dysgeusia and provide a therapy treatment for obesity.

The distal electrodes 108a, 108b may be individually placed on the chroda tympani nerve and/or the pharyngeal braches, respectively, of a patient. The electrical lead assemblies 106a, 106b up-regulate and/or down-regulate nerves of the patient based on the therapy signals. In another embodiment, an additional electrode is adapted to be placed on a glossopharyngeal nerve, and/ or tissue containing baroreceptors. For placement on tissue containing baroreceptors, an electrode may be placed intravascularly or extravascularly. In other embodiments, however, fewer or more electrodes can be placed on or near fewer or more nerves. In embodiments, the first and additional electrodes are each placed on the same nerve or on different nerves.

The signal generator generates electrical signals in the form of electrical impulses according to a programmed regimen. In one embodiment, the therapy program includes a closed loop system that detects a patient's eating behavior. Constant electrical signals may be sent to modify taste perception at a delay period following the onset of consumption. A patient would be able to enjoy the start of a meal but stop eating early due to the food not inducing a rewarding taste effect. This therapy program would decrease caloric intake and induce weight loss. It will be important to have the program run on a delay period as constant electrical signals sent to gustatory afferents would induce a continuous distorted taste perception in the absence of food. This constant manipulation of gustatory afferents would very likely affect efferent information such as salivation; inducing a constant dry mouth or drooling. In embodiments, the signals were intermittent, and periodic.

Features may be incorporated into the signal generator 102 for purposes of the safety and comfort of the patient. In some embodiments, the patient's comfort would be enhanced by ramping the application of the signal up. The device may also have a clamping circuit to limit the maximum voltage (20 volts for example) deliverable to the cranial nerves, to prevent nerve damage.

In some embodiments, the signal generator 102 is configured to deliver a signal of about 200 Hz to 25 kHz, 200 Hz to about 15kHz, 200 Hz to about 10 kHz, 200 to 5000 Hz, 250 to 5000 Hz, 300 to 5000 Hz, 400 to 5000 Hz, 500 to 5000 Hz, 200 to 2500 Hz, 300 to 2500 Hz, 400 to 2500 Hz, 500 to 2500 Hz, and any frequencies in between 200 Hz to 25 kHz or combinations thereof.

Example of calculations based on High Impedance electrode

Stimulation of neural tissue using low impedance electrodes is typically achieved using charge balanced biphasic current pulses to minimize the generation of direct current and the production of harmful electrochemical products. The extent to which current affects the nerve can be modeled using a simplified RC circuit. The RC circuit represents the nerve to electrode interface. In this system, the electrode to nerve capacitance is generally high (in the order of tens to hundreds of pF), while the resistance is low (in the order of tens of Ohms).

In a current regulated device, the voltage across low impedance electrodes will quickly rise due to current flowing across the impedance of the nerve membrane. With time, the voltage will keep rising, albeit at a slower rate, due to charge filling the electrode to nerve capacitance. (See Figure 5A (i and ii)). In a constant voltage regulated device, there is an initial current spike due to charging the capacitance of the nerve and electrode system. Figure 5B (ii and iii). The remaining current will be essentially determined by the parallel resistance of the nerve. In the case of a system with a typical low impedance electrode, the current is maintained at a higher level by passage of the current through the nerve.

While not meant to limit the disclosure, it is thought that placing a voltage or current signal on electrodes on or near a nerve, leads to the formation of an electric field that influences the ion gates in the nerve, and in the case of a high frequency signal this results in a down regulation of nerve activity. It is believed that charging the capacitance of the electrode initiates this electrical field and that continued current flow through the electrode maintains this field. The capacitance of a conventional low impedance electrode is a function of the area of the electrode to nerve interface.

By adding a high impedance dielectric coating to the electrode, the capacitance of the electrode will increase equivalent to the dielectric constant of the coating which is typically of the order of 2 to 4 times higher than a conventional low impedance electrode. The resistance of the electrode nerve interface will increase more significantly and can be in the order of 10,000 to 1,000,000 times higher than a conventional low impedance electrode. Figure 5C i and ii. Applying a voltage or current signal on high impedance electrodes will result in the initiation of an electric field as soon as the electrode capacitance is charged, and because the high impedance dielectric coating on the electrode prevents the charge from dissipating, this field can be maintained at lower currents than in conventional electrodes. See Figure 5B(iii). Rapid charging of the capacitance of the electrode using an optimal voltage or current and careful matching of the electrode impedance to the nerve and its environment in the body allows for significant reduction in charge required to influence ion gates in nerves. In addition, high impedance electrodes have increased safety profile due to a decrease in the charge/pulse delivered to the nerve.

To illustrate the charge reduction using a high impedance electrode the nerve capacitance is modeled with a simplified parallel plate model.. We estimate that the capacitance of an electrode = ε _Γ ε ₀ *ΑΛ1 where ε _Γ = relative static permittivity, ε ₀ = electric constant, A = the area of the electrodes, and d = the distance between electrodes. In the case of the traditional low impedance electrode ε _Γ is approximately 1. With an electrode surface area of 5 square millimeters (mm ² ) and separation of 2 mm, the capacitance = ε _Γ ε ₀ *ΑΛ1 = (8.854 l0 ^~12 F m ^_1 )* l *(5 mm ² /2 mm) = 22 pFarads (pF). The charge on the low impedance electrode at a stimulation voltage of 8 V equals voltage* capacitance = (8V)*(22 pF) = 0.18 nC. The resistive aspect of the traditional low impedance electrode is modeled at approximately 1000 Ohms. Ohms law can be used to approximate the amount of current necessary to sustain the electric field. This current equals voltage/resistance = 4.6 V/1000 Ohms = 0.0046 amps. At 5000 Hz, the pulse width for a biphasic pulse is (1/5000 Hz)/2 = 0.0001 seconds. Since charge = pulse width * current, the charge necessary to sustain the electric field equals 0.0046 amps * 0.0001 seconds = 460 nC.

By coating electrodes with a limited conducting CNT and /or polymeric material, the impedance increases significantly, for example, ranging from 900 ohms to 3.4 megOhms (Figure 5Ci and ii). When the surface area and distance between the high and low impedance electrodes remains fixed, the capacitance only changes by ε _Γ for the material applied to the electrode. In one embodiment, the capacitance increases by approximately 3 times to 66pF. The charge on the electrode at a stimulation voltage of 8 V equals voltage*capacitance = (8V)*(66 pF) = 0.53 nC. Assuming the high impedance electrode is approximately 100,000 Ohms, the current to sustain the electric field equals voltage/resistance = 8 V/100,000 Ohms = 0.00008 amps. At 5000 Hz, the pulse width for a biphasic pulse is (1/5000 Hz)/2 = 0.0001 seconds. Since charge = pulse width * current, the charge necessary to sustain the electric field equals 0.00008 amps * 0.0001 seconds = 8 nC. This is a decrease by a factor of about 60 in the charge/pulse necessary to induce a conduction block under the same conditions as compared to a low impedance electrode with an impedance of 1000 Ohms or less.

Coating electrodes with a limited conductive CNT and/or polymeric material would also lower the charge/pulse with frequencies less than 200 Hz. For a non- coated electrode with an electrode surface area of 5 square millimeters (mm2) and separation of 2 mm, the capacitance = 8re0*A/d = (8.854x 10-12 F m-l)* l *(5 mm2/2 mm) = 22 pFarads (pF). The charge on the low impedance electrode at a stimulation voltage of 8 V equals voltage*capacitance = (8V)*(22 pF) = 0.18 nC.

The resistive aspect of the traditional low impedance electrode is modeled at approximately 1000 Ohms. Ohms law can be used to approximate the amount of current necessary to sustain the electric field. This current equals voltage/resistance = 4.6 V/1000 Ohms = 0.0046 amps. At 100 Hz, the pulse and a pulse width of 0.00025 seconds. Since charge = pulse width * current, the charge necessary to sustain the electric field equals 0.0046 amps * 0.00025 seconds = 1150 nC.

By coating electrodes with a limited conducting CNT and /or polymeric material, the impedance increases significantly, for example, ranging from 900 ohms to 3.4 megOhms (Figure 5C i and ii). When the surface area and distance between the high and low impedance electrodes remains fixed, the capacitance only changes by 8 _r for the material applied to the electrode. In one embodiment, the capacitance increases by approximately 3 times to 66pF. The charge on the electrode at a stimulation voltage of 8 V equals voltage*capacitance = (8V)*(66 pF) = 0.53 nC. Assuming the high impedance electrode is approximately 100,000 Ohms, the current to sustain the electric field equals voltage/resistance = 8 V/100,000 Ohms = 0.00008 amps. At 100 Hz, the pulse width of 0.00025 seconds. Since charge = pulse width * current, the charge necessary to sustain the electric field equals 0.00008 amps * 0.00025 seconds = 80 nC. This is a decrease by a factor of about 60 in the charge/pulse necessary to induce a conduction block under the same conditions as compared to a low impedance electrode with an impedance of 1000 Ohms or less.

The decrease in the amount of charge required to achieve nerve conduction downregulation and /or upregulation can be determined by selecting a current or voltage, electrode area and then selecting the appropriate coating and thickness to achieve a high impedance value. Increasing the impedance of the electrode aims to reduce the current necessary to sustain the electrical field to the lowest value that allows down or up regulation of the nerve. Charge per pulse can be calculated for electrodes of differing impedance values.

Table 1 summarizes the calculated charge/pulse with different impedance electrodes.

Table 1 : Summary of calculated charge/pulse using various impedance electrodes The voltage is 8 V, the frequency is 5000 Hz, the electrode surface area is 5 mm ² and the separation is 2 mm. Note: as the impedance increases the sustaining charge/pulse approaches the capacitive charge/pulse.

Modifications and equivalents of disclosed concepts such as those which might readily occur to one skilled in the art are intended to be included in the scope of the claims which are appended hereto. In addition, this disclosure contemplates application of a combination of electrical signal treatment by placement of electrodes on one or more nerves. This disclosure contemplates application of a therapy program to down regulate neural activity by application of an electrical signal treatment by placement of electrodes on one or more nerves. This disclosure contemplates application of a therapy program to up regulate neural activity by application of electrical signal treatment by placement of electrodes on one or more nerves. Any publications referred to herein are hereby incorporated by reference.