Method and electrical stimulation device for interferential stimulation using an axially biased stimulation field

Abstract

One example method for electrical stimulation of a subject includes forming a plurality of circuits with implantable electrodes positioned within the subject, transmitting a signal at a first frequency through a first circuit of the plurality of circuits, the first circuit generating a first electric field, and transmitting a signal at a second frequency through a second circuit of the plurality of circuits, the second circuit generating a second electric field, the implantable electrodes being positioned in a substantially linear configuration along the same axis such that the first and second electric fields are in an axial bias configuration, and the first and second electric fields interfere with each other in an overlapping region to generate a beat signal.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This disclosure claims priority to U.S. Patent Application No. 17 / 900,559, filed August 31, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates generally to electrical stimulation of a subject, and more particularly to devices and methods for electrical stimulation using interferential current patterns to treat specific conditions. [Background technology]

[0003] Electrical stimulation of the posterior spinal cord, or spinal cord stimulation (SCS), has developed into an effective therapeutic tool for treating chronic pain conditions. However, little is known about the activated sites and neural mechanisms that promote SCS-induced pain relief and functional changes in somatic and visceral structures.

[0004] Spinal cord stimulation is most commonly used for patients with chronic intractable pain syndromes. Spinal cord stimulation is also useful for treating movement disorders and is occasionally used after head trauma. However, one of the complications of SCS is adaptation, or habituation, to the stimulation signal. Adaptation occurs when the body becomes habituated or used to an activity or signal and begins to ignore or "pay attention." Adaptation can be minimized by varying the signal or by continually shifting the signal focus.

[0005] Dorsal column stimulation (DCS), or SCS, using electrical current patterns has been shown to be beneficial for treating chronic pain disorders in patients. Traditional SCS stimulation can be limited by the spread of the stimulation field into the cerebrospinal fluid (CSF) as stimulation intensity increases. This is due to the highly conductive nature of cerebrospinal fluid (CSF) compared to the poor conductivity of spinal cord tissue itself. Patient satisfaction with electrical stimulation is often compromised because activation of adjacent neural structures can cause discomfort, motor contractions, and severe pain. Therefore, the effectiveness of this treatment is limited.

[0006] Electrical stimulation has also been shown to be useful in treating certain other conditions, although the success of treatment is often limited to the ability of stimulation to be effectively delivered and maintained at the subject's pain site. Summary of the Invention

[0007] In an embodiment, a method for electrical stimulation of a subject is described, the method including forming a plurality of circuits using implantable electrodes positioned within the subject's body, transmitting a signal at a first frequency through a first circuit of the plurality of circuits, the first circuit generating a first electric field, transmitting a signal at a second frequency through a second circuit of the plurality of circuits, and the second circuit generating a second electric field, the implantable electrodes being positioned in a substantially linear configuration along the same axis such that the first and second electric fields are in an axial bias configuration, and the first and second electric fields interfere with each other in an overlapping region to generate a beat signal.

[0008] In another embodiment, a method for electrical stimulation of a subject is described, the method including transmitting a signal at a first frequency through a first circuit formed between a first pair of implantable electrodes positioned within the subject, the first circuit generating a first electric field, and transmitting a signal at a second frequency through a second circuit formed between a second pair of implantable electrodes positioned within the subject, the second circuit generating a second electric field, the first pair of implantable electrodes and the second pair of implantable electrodes being positioned in a substantially linear configuration along the same axis such that the first electric field and the second electric field are in an axial bias configuration, and the first electric field and the second electric field interfere with each other in a region of overlap to generate a beat signal.

[0009] In another embodiment, an electrical stimulation device for electrical stimulation of a subject is described, the device including an interference current generator generating an interference alternating current output including a first signal and a second signal, and a plurality of circuits formed with implantable electrodes. The implantable electrodes have a first end and a second end, the first end coupled to the interference current generator, and the second end configured to be positioned within the subject's body, the first signal being transmitted through a first circuit of the plurality of circuits to generate a first electric field, and the second signal being transmitted through a second circuit of the plurality of circuits to generate a second electric field, the implantable electrodes being positioned in a substantially linear configuration along the same axis such that the first electric field of the first circuit and the second electric field of the second circuit are in an axial bias configuration. The first electric field and the second electric field interfere with each other in an overlapping region to generate a beat signal.

[0010] These and other aspects, advantages and alternatives will become apparent to those skilled in the art from a reading of the following detailed description, with appropriate reference to the accompanying drawings. [Brief explanation of the drawings]

[0011] Many aspects of the present disclosure can be understood with reference to the following drawings, in which elements are not necessarily to scale. Moreover, in the drawings, like reference numerals indicate corresponding parts throughout the several views.

[0012] [Figure 1] FIG. 1 illustrates an example of an electrical stimulation device for electrical stimulation of a subject, according to an exemplary embodiment.

[0013] [Figure 2] FIG. 2 illustrates an exemplary quadripolar lead provided with implantable electrodes, according to an exemplary embodiment.

[0014] [Figure 3] FIG. 3 shows a single lead with multiple electrodes that are multiple circuits formed to generate electric fields in an axial bias configuration for electrical stimulation, according to an exemplary embodiment.

[0015] [Figure 4] FIG. 4 shows a single lead with multiple electrodes formed into multiple circuits to generate electric fields in an axial bias configuration for electrical stimulation, according to another exemplary embodiment.

[0016] [Figure 5] FIG. 5 shows a single lead with multiple electrodes formed into multiple circuits to generate electric fields in an axial bias configuration for electrical stimulation, according to another exemplary embodiment.

[0017] [Figure 6] FIG. 6 shows a single lead with multiple electrodes formed into multiple circuits to generate electric fields in an axial bias configuration for electrical stimulation, according to another exemplary embodiment.

[0018] [Figure 7]FIG. 7 shows a single lead with multiple electrodes formed into multiple circuits to generate electric fields in an axial bias configuration for electrical stimulation, according to another exemplary embodiment.

[0019] [Figure 8] FIG. 8 shows a single lead with multiple electrodes formed into multiple circuits to generate electric fields in an axial bias configuration for electrical stimulation, according to another exemplary embodiment.

[0020] [Figure 9] FIG. 9 shows a single lead with multiple electrodes formed into multiple circuits to generate electric fields in an axial bias configuration for electrical stimulation, according to another exemplary embodiment.

[0021] [Figure 10] FIG. 10 illustrates a dual-lead configuration having multiple electrodes circuited to generate electric fields in an axial bias configuration for electrical stimulation, according to an exemplary embodiment.

[0022] [Figure 11] FIG. 11 illustrates a dual-lead configuration having multiple electrodes circuited to generate electric fields in an axial bias configuration for electrical stimulation, according to an exemplary embodiment.

[0023] [Figure 12] FIG. 12 includes graphs illustrating sinusoidal representations of a first signal, a second signal, and a resulting beat signal, according to an example embodiment.

[0024] [Figure 13] FIG. 13 shows a flowchart of an example of a method for electrical stimulation of a subject, according to an exemplary embodiment.

[0025] [Figure 14] FIG. 14 shows a flowchart of an example of a method for electrical stimulation of a subject, according to an exemplary embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0026] Exemplary methods and systems are described herein. It should be understood that the words “example,” “exemplary,” and “illustrative” are used herein to mean “serving as an example, instance, or illustration.” Any embodiment or feature described herein as “example,” “exemplary,” or “illustrative” should not necessarily be construed as preferred or advantageous over other embodiments or features. The exemplary embodiments described herein are not meant to be limiting. It will be readily understood that the aspects of the present disclosure, as generally described and illustrated in the figures herein, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are expressly contemplated herein.

[0027] The embodiments described herein provide devices and methods for electrical stimulation of a subject, such as for many different types of treatments and applications. In embodiments, an electrical stimulation device is provided that includes implanted electrodes, and interferential stimulation is used to generate a beat frequency signal that is directed to an appropriate target within the subject. The effective area of ​​stimulation is controlled by the number of electrodes, the location of the electrodes, and the direction of the electrode interferometric pattern.

[0028] The interferometric current provides directional control, reduced adaptation or habituation, and increased depth of penetration compared to other standard implanted stimulation systems and associated surgical leads. The output amplitude in each circuit can be modulated to increase the area of ​​targeted stimulation. In embodiments, the beat frequency signal is directional and / or depth of penetration controlled to target specific areas of the subject using modulation of the circuit output.

[0029] FIG. 1 illustrates an example of an electrical stimulation device 100 for electrical stimulation of a subject, according to an exemplary embodiment. The electrical stimulation device 100 includes a plurality of circuits formed using an interferential current generator 102 that generates an interferential alternating current output including a first signal 104 and a second signal 106, and an implanted electrode 108. The implanted electrode 108 has a first end and a second end. The first end is coupled to the interferential current generator 102, and the second end is configured to be positioned within the subject's body, such as in the subject's tissue 110. The first end is connected to the second end via a wire or wired pad. The second end includes a portion of the electrode capable of delivering electrical pulses and may therefore be an electrode pad. In one example, the implanted electrode 108 (or a portion of the implanted electrode including the electrode pad) is implanted in the dura mater in the epidural space 112 at a predetermined location adjacent to the subject's spinal cord 114. Other use examples are described below.

[0030] The electrical stimulation device 100 described herein may be completely implanted within a subject's body, or a portion of the electrical stimulation device 100 may be implanted and a portion may remain external to the subject's body. As an example, the implanted electrode 108 may be implanted as described above, and the interferometric current generator 102 and power source may be external and coupled to the implanted electrode 108 via wires. In another example, the coupling from the interferometric current generator 102 to the implanted electrode 108 may be via a wireless link (e.g., a radio frequency (RF) link), such that the electrode is implanted and the interferometric current generator 102 is not. The RF carrier frequency may be in the MHz, GHz, or THz range and will induce a current in an implanted receiver linked or connected to the implanted electrode 108. The RF carrier frequency may be in the range of about 1 MHz to about 20 THz.

[0031] In yet another embodiment, the interferential current generator 102 is implanted within the subject (and the power source connected to the interferential current generator 102 may be implanted as well), and the implanted electrode 108 is further implanted. The interferential current generator 102 may be implanted, for example, near or within the brachial plexus or near or below the 12th rib.

[0032] In operation of the electrical stimulation device 100, a first signal 104 is transmitted through a first circuit of the plurality of circuits to generate a first electric field, a second signal 106 is transmitted through a second circuit of the plurality of circuits to generate a second electric field, and the implantable electrodes 108 are positioned in a substantially linear configuration along the same axis such that the first electric field of the first circuit and the second electric field of the second circuit are in an axial bias configuration. The first and second electric fields interfere with each other in the overlap region to generate a beat signal.

[0033] In some embodiments, the electrical stimulation device 100 also includes a processor 116 coupled to the interferential current generator 102, the processor 116 being programmed to send the first signal 104 and the second signal 106 to the interferential current generator 102 at selected frequencies, voltage levels, and time durations.

[0034] The interference current generator 102 includes a pulse generator 118 that generates digital signal pulses, and the processor 116 is connected to or in communication with the pulse generator 118 to generate the digital signal pulses to approximate a sinusoidal output waveform. For example, the output can be a continuous waveform such as a sine wave, a quasi-sine wave, or an in-phase sine wave. In other embodiments, the output includes a square wave.

[0035] Pulse generator 118 generates individual pulses of different widths and combined amplitudes. In some embodiments, the pulse widths range from about 0 to about 2.5 microseconds (ms), from about 2.5 ms to about 5 ms, or from about 5 ms to about 10 ms. When these different pulses are applied to a transformer (not shown), a quasi-sine wave is generated.

[0036] The pulse generator 118 also generates a range of outputs, such as amplitudes within the ranges of about 5 mA to about 9 mA, about 9 mA to about 10 mA, and about 10 mA to about 18 mA, depending on the patient's needs for pain treatment.

[0037] Instead of or in addition to a digital signal processor, processor 116 may be or include a field programmable gate array (FPGA) used to shape multiple pulse waveforms to approximate the output of a sine wave generator. FPGAs are integrated circuits that can be programmed in the field after manufacture, allowing their users to tailor the circuit output as desired. Thus, in alternative embodiments, processor 116 may be replaced with an FPGA. FPGA devices can enable complex digital signal processing applications such as finite impulse response filters, forward error correction, modulation-demodulation, encryption, and other applications.

[0038] Processor 116 may include internal memory (non-transitory memory as well as buffer / transitory type memory) for storing instructions for execution to cause electrical stimulator 100 to perform the functions described herein. Additionally or alternatively, in one example, electrical stimulator 100 includes a separate internal memory with which the processor is in communication (via conventional bus communication), the internal memory storing instructions for execution to cause electrical stimulator 100 to perform the functions described herein.

[0039] The electrical stimulator 100 may also include additional components, such as a power supply and other circuitry for performing the functions described herein.

[0040] In an embodiment, as described above, the processor 116 communicates with the interferometric current generator 102 to cause the interferometric current generator 102 to transmit different signals at different time periods for waveform generation for electrical stimulation therapy.

[0041] FIG. 2 illustrates exemplary quadripolar leads 120a-b on which implanted electrodes 108 are provided, according to an exemplary implementation. While FIG. 2 illustrates two quadripolar leads 120a-b, more or fewer leads may be used depending on the electrode placement and arrangement. Each quadripolar lead 120a-b includes multiple implanted electrodes, represented as four electrode pads 122a-d and 124a-d. The use of quadripolar leads allows for a larger targeted therapeutic stimulation area on the subject. However, the electrical stimulation device of the present disclosure may also be applied to the use of two bipolar or octapolar lead systems, as well as other suitable devices including any number of electrode pads, for example, 4, 6, 8, 10, . . . , or up to 30 or 32. The quadripolar leads 120a-b include first ends 126a-b that couple to the current generator 102. The implanted electrodes 108 can be activated in a variety of combinations and patterns, not just those shown in the drawings.

[0042] During operation, the current generator 102 generates an interference output including a first signal 104 and a second signal 106 having different first and second frequencies. Selected ones of the implanted electrodes 108 transmit one of the first signal 104 and the second signal 106 to form separate circuits. When the first circuit (formed between the two electrodes) and the second circuit (formed between the two electrodes) interfere, the resulting beat frequency is the difference between the frequencies of the two circuits, which add in amplitude and are greater than either circuit alone. In other embodiments, the resulting beat frequency signal can have a frequency in the range of greater than 250 Hz to approximately 15,000 Hz.

[0043] In many of the examples described below, multiple circuits are formed between implanted electrodes 108 in some manner. For example, multiple circuits can be formed using three electrodes, including one electrode that is common between two circuits. In other examples, multiple circuits can be formed using four electrodes, such that separate circuits are formed between separate pairs of electrodes. Furthermore, multiple circuits can be formed using electrodes on a single lead, or multiple circuits can be formed using two separate leads positioned in a substantially linear configuration, approximately end-to-end, with the distance between the first and second leads, measured perpendicular to the same axis, being less than about 2 mm.

[0044] Thus, in some embodiments, the implantable electrodes 108 are included on a single lead, and the implantable electrodes 108 are independently controllable to be arranged as positive and negative pairs to form first and second circuits using the single lead. Furthermore, a single lead can be used to form multiple circuits, such that a first circuit is between a first and a second implantable electrode, a second circuit is between the first and a third implantable electrode, and the first and second circuits have a common implantable electrode. In other examples, a single lead can be used to form multiple circuits, such as a first circuit is between a first and a second implantable electrode, and a second circuit is between a third and a fourth implantable electrode.

[0045] In yet another embodiment, the implantable electrodes include a first pair of implantable electrodes and a second pair of implantable electrodes positioned in a substantially linear configuration along a coaxial line.

[0046] In summary, multiple circuits can be formed in a number of ways, including using three electrodes on a single lead, using four electrodes on a single lead, using more than four electrodes on a single lead (e.g., for more than two circuits), using three electrodes from two different leads, using four electrodes from two different leads, or using more than four electrodes from two different leads. Examples are illustrated and described below.

[0047] 3 shows a single lead 130 having multiple electrodes formed into multiple circuits for generating electric fields in an axial bias configuration for electrical stimulation, according to an exemplary embodiment. Lead 130 includes implantable electrodes 132a-d, and in one example, lead 130 can take the form of, for example, one of leads 120a-b shown in FIG. 2 (although lead 130 is shown to include additional electrodes that are not labeled).

[0048] Each of the implanted electrodes 132a-d is independently controllable to operate as either a negative or positive electrode, allowing any combination of the implanted electrodes 132a-d to be selected to form one or more circuits. For physiological purposes, nerves are polarized in their resting state, with a negative internal charge, ready to fire. The electrons (negative internal charge) attract positive charges on the outside of the nerve, resulting in depolarization. Thus, physiologically, the negative electrode is considered the negative contact point, and the positive electrode is considered the positive contact point, attracting negative charges, since the positive electrode is where the negative charge accumulates.

[0049] 3, a first circuit is formed between implanted electrodes 132a and 132b by placing implanted electrode 132a as the negative electrode or contact and implanted electrode 132b as the positive electrode or contact. A second circuit is formed between implanted electrodes 132a and 132c by placing implanted electrode 132c as another positive electrode or contact. In this example, the first and second circuits share implanted electrode 132a as the positive electrode, and implanted electrode 132d is not used.

[0050] 3, the three electrodes of lead 130 are used to form two separate circuits. Interference current generator 102 is then operated to transmit a signal at a first frequency through the first circuit, generating a first electric field 134, and a signal at a second frequency through the second circuit, generating a second electric field 136, with the first electric field 134 and the second electric field 136 interfering with each other in an overlap region 138 to generate a beat signal. Where first electric field 134 and second electric field 136 overlap or overlap, the resulting beat signal will be the difference between the frequencies of the two circuits, and will be additive in amplitude and larger than either circuit alone.

[0051] In FIG. 3, implanted electrodes 132a, 132b, and 132c are positioned in a substantially linear configuration along the same axis such that first electric field 134 and second electric field 136 are in an axial bias configuration.

[0052] 4 shows a single lead 130 having multiple electrodes with multiple circuits formed therein to generate electric fields in an axial bias configuration for electrical stimulation according to another exemplary implementation. In FIG. 4, a first circuit is formed between implanted electrodes 132a and 132b by positioning implanted electrode 132a as the positive electrode or contact and implanted electrode 132b as the negative electrode or contact. A second circuit is formed between implanted electrodes 132b and 132c by positioning implanted electrode 132c as another positive electrode or contact. In this example, the first and second circuits share implanted electrode 132b as the negative electrode.

[0053] 4, the three electrodes of lead 130 are used to form two separate circuits. Interference current generator 102 is then operated to transmit a signal at a first frequency through the first circuit, generating a first electric field 134, and a signal at a second frequency through the second circuit, generating a second electric field 136, with the first electric field 134 and the second electric field 136 interfering with each other in an overlap region 138 to generate a beat signal. Where first electric field 134 and second electric field 136 overlap or overlap, the resulting beat signal will be the difference between the frequencies of the two circuits, and will be additive in amplitude and larger than either circuit alone.

[0054] Similar to the arrangement of FIG. 3, in FIG. 4, the implanted electrodes 132a, 132b, and 132c are positioned in a substantially linear configuration along the same axis such that the first electric field 134 and the second electric field 136 are in an axial bias configuration.

[0055] Thus, as shown in the examples of Figures 3 and 4, a single lead 130 includes multiple electrodes arranged in a linear electrode array along an axis, and changing the selection of electrodes along the single lead changes the longitudinal location of the beat signal (or overlap region 138). Similarly, the longitudinal location of the beat signal can be changed by changing the configuration of the first and second circuits to operate on or differently from multiple electrodes in the linear electrode array. For example, changing the positive polarity of the shared or common electrode 132b in Figure 3 to the negative polarity in Figure 4 changes how the electric fields interfere to generate the beat signal.

[0056] The interference current generator 120 can be operated in a number of ways to transmit the first and second signals 104, 106 at different frequencies. In one example, transmitting the signal at the first frequency through the first circuit includes transmitting a signal at a frequency between about 1,000 Hz and about 20,000 Hz, and transmitting the signal at the second frequency through the second circuit includes transmitting a signal at a frequency between about 1,000 Hz and about 20,000 Hz. For beat signal generation, the first frequency is different from the second frequency.

[0057] The frequencies of the signals transmitted through the first and second circuits may be within any range that results in a beat signal having a frequency, for example, within the range of about 0 to about 20,000 Hz, or within the range of greater than 0 Hz to about 5,000 Hz. The beat signal frequency results from interference of the two signals from the first and second circuits (e.g., a 10,000 Hz frequency on the first circuit creating a first electric field that interferes with a second electric field created by a 12,000 Hz frequency on the second circuit, resulting in a beat signal frequency of about 2,000 Hz).

[0058] Based on the combination of frequencies used and transmitted in the first and second circuits, the beat signal may range from greater than 0 Hz to about 5,000 Hz. Thus, in embodiments, the signal may range from about 12,000 Hz to about 15,000 Hz, from about 13,000 Hz to about 15,000 Hz, from about 14,000 Hz to about 15,000 Hz, from about 10,000 Hz to about 15,000 Hz, from about 6,000 Hz to about 9,000 Hz, from about 7,000 Hz to about 9,000 Hz, from about 8,000 Hz to about 9,000 Hz, from about 9,000 Hz to about 12,000 Hz, or The frequency range may be transmitted in a frequency range of about 10,000 Hz to about 12,000 Hz, a frequency range of about 11,000 Hz to about 13,000 Hz, a frequency range of about 3,000 Hz to about 5,000 Hz, a frequency range of about 3,000 Hz to about 7,000 Hz, a frequency range of about 3,000 Hz to about 6,000 Hz, a frequency range of about 5,000 Hz to about 8,000 Hz, a frequency range of about 1,000 Hz to about 5,000 Hz, or any other range of 1,000 Hz to about 20,000 Hz.

[0059] Thus, any signal within the range of approximately 1,000 Hz to 20,000 Hz can be used and transmitted to the first and second circuits to cause interference in the electric fields, resulting in a beat signal within the range of approximately 0 to 5,000 beats per second (BPS).

[0060] 5 shows a single lead 130 having multiple electrodes with multiple circuits formed therein to generate electric fields in an axial bias configuration for electrical stimulation according to another exemplary implementation. In FIG. 5, a first circuit is formed between implanted electrodes 132a and 132c by positioning implanted electrode 132a as the negative or negative contact and implanted electrode 132c as the positive or positive contact. A second circuit is formed between implanted electrodes 132b and 132d by positioning implanted electrode 132b as the positive or positive contact and implanted electrode 132d as the negative or negative contact. In this example, the first and second circuits do not share any implanted electrodes, and each of the first and second circuits is formed using a different pair of implanted electrodes.

[0061] 5, the four electrodes of lead 130 are used to form two separate circuits. Interference current generator 102 is then operated to transmit a signal at a first frequency through the first circuit, generating a first electric field 134, and a signal at a second frequency through the second circuit, generating a second electric field 136, with the first electric field 134 and the second electric field 136 interfering with each other in an overlap region 138 to generate a beat signal. Where first electric field 134 and second electric field 136 overlap or overlap, the resulting beat signal will be the difference between the frequencies of the two circuits, and will be additive in amplitude and larger than either circuit alone.

[0062] In FIG. 5, implanted electrodes 132a, 132b, 132c, and 132d are positioned in a substantially linear configuration along the same axis such that first electric field 134 and second electric field 136 are in an axial bias configuration.

[0063] FIG. 6 shows a single lead 130 having multiple electrodes with multiple circuits formed therein to generate electric fields in an axial bias configuration for electrical stimulation according to another exemplary implementation. In FIG. 6, a first circuit is formed between implanted electrodes 132a' and 132c by positioning implanted electrode 132a' as the positive or positive contact and implanted electrode 132c as the negative or negative contact. A second circuit is formed between implanted electrodes 132b' and 132d' by positioning implanted electrode 132b' as the negative or negative contact and implanted electrode 132d' as the positive or positive contact. In this example, the first and second circuits do not share any implanted electrodes, and each of the first and second circuits is formed using a different pair of implanted electrodes. Additionally, in FIG. 6, implanted electrodes 132a, 132b, and 132d are inactive.

[0064] 6, the four electrodes of lead 130 are used to form two separate circuits. Interference current generator 102 is then operated to transmit a signal at a first frequency through the first circuit, generating a first electric field 134, and a signal at a second frequency through the second circuit, generating a second electric field 136, with the first electric field 134 and the second electric field 136 interfering with each other in an overlap region 138 to generate a beat signal. Where first electric field 134 and second electric field 136 overlap or overlap, the resulting beat signal will be the difference between the frequencies of the two circuits, and will be additive in amplitude and larger than either circuit alone.

[0065] In FIG. 6, implanted electrodes 132a', 132b', 132c, and 132d' are positioned in a substantially linear configuration along the same axis such that first electric field 134 and second electric field 136 are in an axial bias configuration.

[0066] 5 and 6, a first circuit is formed between a first pair of implantable electrodes positioned within the subject, and a second circuit is formed between a second pair of implantable electrodes positioned within the subject. The first pair of implantable electrodes and the second pair of implantable electrodes are each positioned in a substantially linear configuration along the same axis such that the first electric field and the second electric field are in an axial bias configuration. Furthermore, the first pair of implantable electrodes and the second pair of implantable electrodes are included on a single lead 130. As shown, changing the selection of the first electrode of the first pair of implantable electrodes on the single lead 130 changes the longitudinal position of the beat signal.

[0067] 7-9 show further examples of using a single lead 130 with four electrodes operated in different configurations to form multiple circuits and resulting beat signals at different locations.

[0068] FIG. 7 illustrates a single lead 130 having multiple electrodes with multiple circuits formed therein to generate electric fields in an axial bias configuration for electrical stimulation according to another exemplary implementation. In FIG. 7, the single lead 130 is shown to include eight electrodes labeled 132a-h. A first circuit is formed between the pair of implanted electrodes 132a and 132d by positioning implanted electrode 132a as the positive or positive contact and implanted electrode 132d as the negative or negative contact. A second circuit is formed between the pair of implanted electrodes 132c and 132f by positioning implanted electrode 132c as the negative or negative contact and implanted electrode 132f as the positive or positive contact. In this example, the first and second circuits do not share any implanted electrodes; each of the first and second circuits is formed using a different pair of implanted electrodes. Additionally, in FIG. 7, implanted electrodes 132b, 132e, 132g, and 132h are inactive.

[0069] 7, the four electrodes of lead 130 are used to form two separate circuits. Interference current generator 102 is then operated to transmit a signal at a first frequency through the first circuit, generating a first electric field 134, and a signal at a second frequency through the second circuit, generating a second electric field 136, with first electric field 134 and second electric field 134 interfering with each other in overlap region 138 to generate a beat signal.

[0070] FIG. 8 shows a single lead 130 having multiple electrodes with multiple circuits formed therein to generate electric fields in an axial bias configuration for electrical stimulation according to another exemplary implementation. In FIG. 8, a first circuit is formed between the pair of implanted electrodes 132b and 132f by positioning implanted electrode 132b as the negative or negative contact and implanted electrode 132f as the positive or positive contact. A second circuit is formed between the pair of implanted electrodes 132a and 132c by positioning implanted electrode 132a as the positive or positive contact and implanted electrode 132c as the negative or negative contact. In this example, the first and second circuits do not share any implanted electrodes, and each of the first and second circuits is formed using a different pair of implanted electrodes. Additionally, in FIG. 8, implanted electrodes 132d, 132e, 132g, and 132h are inactive.

[0071] 8, the four electrodes of lead 130 are used to form two separate circuits. Interference current generator 102 is then operated to transmit a signal at a first frequency through the first circuit, generating a first electric field 134, and a signal at a second frequency through the second circuit, generating a second electric field 136, which interfere with each other in an overlap region 138, generating a beat signal.

[0072] FIG. 9 shows a single lead 130 having multiple electrodes in which multiple circuits are formed to generate electric fields in an axial bias configuration for electrical stimulation according to another exemplary implementation. In FIG. 9, a first circuit is formed between the pair of implanted electrodes 132c and 132h by positioning implanted electrode 132c as the negative or negative contact and implanted electrode 132h as the positive or positive contact. A second circuit is formed between the pair of implanted electrodes 132a and 132f by positioning implanted electrode 132a as the positive or positive contact and implanted electrode 132f as the negative or negative contact. In this example, the first and second circuits do not share any implanted electrodes, and each of the first and second circuits is formed using a different pair of implanted electrodes. Additionally, in FIG. 9, implanted electrodes 132b, 132d, 132e, and 132g are inactive.

[0073] 9, the four electrodes of lead 130 are used to form two separate circuits. Interference current generator 102 is then operated to transmit a signal at a first frequency through the first circuit, generating a first electric field 134, and a signal at a second frequency through the second circuit, generating a second electric field 136, which interfere with each other in an overlap region 138, generating a beat signal.

[0074] In each of Figures 7-9, the implanted electrodes are all positioned in a substantially linear configuration along the same axis such that the first field 134 and the second field 136 are in an axial bias configuration. As shown in Figures 7-9, by changing the selection of electrodes for use in forming the multiple circuits, the location of the beat signal can be shifted longitudinally along the axis. Additionally, the shape or focus of the beat signal can be changed to be narrower (as shown in Figure 7) or more elongated (as shown in Figure 9).

[0075] FIG. 10 shows a dual-lead configuration having multiple electrodes in which multiple circuits are formed to generate an electric field in an axial bias configuration for electrical stimulation, according to an exemplary embodiment. In FIG. 10, a first lead 140 and a second lead 142 each include an implanted electrode. Two circuits are formed using three electrodes, with each circuit sharing a common negative or negative contact. For example, a first circuit is formed between an implanted electrode 144 on lead 142 (positioned as the positive or positive contact) and an implanted electrode 146 on lead 142 (positioned as the negative or negative contact). A second circuit is formed between an implanted electrode 148 on lead 140 (positioned as the positive or positive contact) and an implanted electrode 146 on lead 142 (positioned as the negative or negative contact).

[0076] 10, three electrodes (one on lead 140 and two on lead 142) are used to form two separate circuits. Interference current generator 102 is then operated to transmit a signal at a first frequency through the first circuit to generate a first electric field 150 and a signal at a second frequency through the second circuit to generate a second electric field 152, which interfere with each other in an overlap region 154 to generate a beat signal.

[0077] In Figure 10, the first lead 140 and the second lead 142 are positioned in a substantially linear configuration along the same axis, and the distance between the first lead 140 and the second lead 142, measured perpendicular to the same axis, is less than about 2 mm. In Figure 10, the first lead 140 and the second lead 142 are shown immediately adjacent to each other, such that the distance between the first lead 140 and the second lead 142, measured perpendicular to the same axis, is effectively 0 mm.

[0078] In other examples, the dual lead arrangement is implemented such that the first lead 140 and the second lead 142 are positioned in a substantially linear configuration approximately end-to-end, and the distance (d) measured perpendicular to the same axis between the first lead 140 and the second lead 142 is less than about 2 mm. In other examples, the distance (d) is less than about 1 mm, between about 1 mm and 2 mm, or between about 0.5 mm and 1 mm.

[0079] FIG. 11 shows a dual-lead configuration having multiple electrodes in which multiple circuits are formed to generate electric fields in an axial bias configuration for electrical stimulation, according to an exemplary embodiment. In FIG. 11, first lead 140 and second lead 142 each include an implanted electrode. Two circuits are formed using four electrodes, with each circuit using a separate electrode pair having one electrode on first lead 140 and one electrode on second lead 142. For example, a first circuit is formed between implanted electrode 156 on lead 140 (positioned as the positive electrode or contact) and implanted electrode 158 on lead 142 (positioned as the negative electrode or contact). A second circuit is formed between implanted electrode 160 on lead 140 (positioned as the positive electrode or contact) and implanted electrode 162 on lead 142 (positioned as the negative electrode or contact).

[0080] 11, four electrodes (two on lead 140 and two on lead 142) are used to form two separate circuits. Interference current generator 102 is then operated to transmit a signal at a first frequency through the first circuit to generate a first electric field 164 and a signal at a second frequency through the second circuit to generate a second electric field 166, which interfere with each other in an overlap region 168 to generate a beat signal.

[0081] 11, the first lead 140 and the second lead 142 are positioned in a substantially linear configuration along the same axis, and the distance between the first lead 140 and the second lead 142, measured perpendicular to the same axis, is less than about 2 mm. Because the first lead 140 and the second lead 142 are shown immediately adjacent to each other in FIG. 11, the first lead 140 and the second lead 142 are in a substantially linear configuration and are arranged approximately end-to-end such that at least one electrode on the first lead 140 is positioned adjacent to at least one electrode on the second lead 142.

[0082] In some examples, the first circuit is formed using an implanted electrode on the first lead 140 and the second circuit is formed using an implanted electrode on the second lead 142. As shown in FIG. 11 , an axial bias configuration can be established by positioning the first lead 140 and the second lead 142 along the same axis.

[0083] Thus, in the examples described herein, an axial bias configuration can be implemented to generate a beat signal useful for electrical stimulation. The axial bias configuration can be established, for example, using three electrodes on a single lead, using four electrodes on a single lead, using three electrodes from two different leads, or using four electrodes from two different leads.

[0084] FIG. 12 includes graphs illustrating sinusoidal representations of a first signal, a second signal, and the resulting beat signal according to an exemplary embodiment. In FIG. 12, a first signal having a first frequency of 4,000 Hz is transmitted through a first circuit (which may be any of the first circuits shown and described with reference to FIGS. 3-11), and a second signal having a second frequency of 4,100 Hz is transmitted through a second circuit (which may be any of the second circuits shown and described with reference to FIGS. 3-11). A beat signal is generated by interference of the electric fields generated by the transmission of the first and second signals. When waves of two different frequencies interfere, the waves are either constructive (additive amplitude) or destructive (subtractive amplitude). When the amplitudes are identical, a clear beat occurs. The frequency of the beat signal is the difference between the two carrier frequencies. In the example shown in FIG. 12, the beat frequency is 100 Hz.

[0085] FIG. 13 shows a flowchart of an example of a method 200 for electrical stimulation of a subject, according to an exemplary embodiment. The method shown in FIG. 13 illustrates a method that may be performed by components of, and may be used by, the stimulation device 100 of FIG. 1, for example. In some examples, the components of the stimulation device 100 may actually be configured and structured (using hardware and / or software) to enable such performance. In other examples, the components of a device and / or system may be arranged to be adapted, enabled, or suitable to perform a function, such as when operated in a particular manner. The method may include one or more operations, functions, or actions, as illustrated by one or more of blocks 202-206. While the blocks are shown sequentially, these blocks may be performed in parallel and / or in a different order than described herein. Also, various blocks may be combined into fewer blocks, divided into additional blocks, and / or eliminated based on a desired implementation.

[0086] In yet another example, the functions of the methods described herein are performed by a circuit (processor) executing instructions stored on a non-transitory computer-readable medium to cause an electrical stimulator to provide stimulation therapy.

[0087] It should be understood that for this and other processes and methods disclosed herein, the flowchart illustrates the functionality and operation of one possible implementation of the present embodiment. The scope of the exemplary embodiments of the present disclosure includes alternative implementations in which functions may be performed out of order from that shown or described, including substantially concurrently or in reverse order, depending on the functionality involved, as will be appreciated by those skilled in the art.

[0088] At block 202, the method 200 includes forming a plurality of circuits with implanted electrodes positioned within the subject.

[0089] In some examples, forming the plurality of circuits with implantable electrodes positioned within the subject includes forming a first circuit between a first implantable electrode and a second implantable electrode and forming a second circuit between the first implantable electrode and a third implantable electrode, in these examples, the first circuit and the second circuit have a common implantable electrode.

[0090] In some examples, forming a plurality of circuits with implantable electrodes positioned within the subject includes forming a first circuit between a first implantable electrode and a second implantable electrode, and forming a second circuit between a third implantable electrode and a fourth implantable electrode.

[0091] In some examples, forming multiple circuits using implanted electrodes positioned within the subject includes forming a first circuit and a second circuit using implanted electrodes on a single lead. The single lead includes multiple electrodes arranged in a linear electrode array, and method 200 optionally includes changing a selection of a first electrode of the first circuit on the single lead to change the longitudinal position of the beat signal. Additionally, method 200 optionally includes changing a configuration of the first circuit and the second circuit operated from among the multiple electrodes of the linear electrode array to change the longitudinal position of the beat signal.

[0092] In some examples, forming a plurality of circuits using implantable electrodes positioned within the subject includes forming a first circuit using implantable electrodes on a first lead and forming a second circuit using implantable electrodes on a second lead.

[0093] At block 204, the method 200 includes transmitting a signal at a first frequency through a first circuit of the plurality of circuits, the first circuit generating a first electric field.

[0094] At block 206, the method 200 includes transmitting a signal at a second frequency through a second circuit of the plurality of circuits, the second circuit generating a second electric field. The implanted electrodes are positioned in a substantially linear configuration along the same axis such that the first and second electric fields are in an axial bias configuration, and the first and second electric fields interfere with each other in an overlap region to generate a beat signal.

[0095] In one example, the first lead and the second lead are positioned in a substantially linear configuration approximately end-to-end, and the distance between the first lead and the second lead, measured perpendicular to the same axis, is less than about 2 mm.

[0096] In one example, the implanted electrodes are independently controllable to be arranged as positive and negative pairs to form first and second circuits.

[0097] In some examples, the method 200 includes transmitting a signal at a first frequency comprising transmitting a signal at a frequency between about 1,000 Hz and about 20,000 Hz, and transmitting a signal at a second frequency comprising transmitting a signal at a frequency between about 1,000 Hz and about 20,000 Hz, the first frequency being different from the second frequency. In some examples, the beat signal has a frequency in the range of greater than 0 Hz to about 5,000 Hz.

[0098] FIG. 14 shows a flowchart of an example of a method 210 for electrical stimulation of a subject, according to an exemplary embodiment. The method shown in FIG. 14 illustrates a method that may be performed by components of, and may be used by, the stimulation device 100 of FIG. 1, for example. In some examples, the components of the stimulation device 100 may actually be configured and structured (using hardware and / or software) to enable such performance. In other examples, the components of a device and / or system may be arranged to be adapted, enabled, or suitable to perform a function, such as when operated in a particular manner. The method may include one or more operations, functions, or actions, as illustrated by one or more of blocks 212-214. While the blocks are shown sequentially, these blocks may be performed in parallel and / or in a different order than described herein. Also, various blocks may be combined into fewer blocks, divided into additional blocks, and / or eliminated based on a desired implementation.

[0099] It should be understood that for this and other processes and methods disclosed herein, the flowchart illustrates the functionality and operation of one possible implementation of the present embodiment. The scope of the exemplary embodiments of the present disclosure includes alternative implementations in which functions may be performed out of order from that shown or described, including substantially concurrently or in reverse order, depending on the functionality involved, as will be appreciated by those skilled in the art.

[0100] At block 212, the method 210 includes transmitting a signal at a first frequency through a first circuit formed between a first pair of implantable electrodes positioned within the subject, the first circuit generating a first electric field.

[0101] At block 214, the method 210 includes transmitting a signal at a second frequency through a second circuit formed between a second pair of implantable electrodes positioned within the subject, the second circuit generating a second electric field.

[0102] In method 210, the first pair of implanted electrodes and the second pair of implanted electrodes are positioned in a substantially linear configuration along the same axis such that the first electric field and the second electric field are in an axial bias configuration, and the first electric field and the second electric field interfere with each other in an overlap region to generate a beat signal.

[0103] In some examples, the first pair of implantable electrodes and the second pair of implantable electrodes are aligned vertically along the longitudinal axis of the spinal cord to form a first circuit and a second circuit, and the first circuit is positioned on the same axis as the second circuit.

[0104] In some examples, the first pair of implantable electrodes and the second pair of implantable electrodes are included on a single lead, and the first pair of implantable electrodes and the second pair of implantable electrodes are independently controllable to be arranged as positive and negative pairs to form first and second circuits. In some examples, the single lead includes multiple electrodes arranged in a linear electrode array, and method 210 further includes altering a selection of a first electrode of the first pair of implantable electrodes on the single lead to alter a longitudinal position of the beat signal.

[0105] In some examples, a first pair of implantable electrodes is included on a first lead and a second pair of implantable electrodes is included on a second lead, and the first lead and second lead are positioned in a substantially linear configuration approximately end-to-end such that the distance (d) between the first lead and the second lead, measured perpendicular to the same axis, is less than about 2 mm.

[0106] In some examples, the substantially linear configuration generally end-to-end includes at least one electrode on the first lead being positioned adjacent to at least one electrode on the second lead.

[0107] In some examples, the method 210 includes transmitting a signal at a first frequency including transmitting a signal at a frequency between about 1,000 Hz and about 20,000 Hz, and transmitting a signal at a second frequency including transmitting a signal at a frequency between about 1,000 Hz and about 20,000 Hz, wherein the first frequency is different from the second frequency. In some examples, the beat signal has a frequency in the range of greater than 0 Hz to about 5,000 Hz.

[0108] The electrical stimulation described herein can be used for many different types of treatments or applications. In one example, a method described herein includes positioning a first pair of implantable electrodes on the dura mater in the epidural space adjacent to a subject's spinal cord and positioning a second pair of implantable electrodes on the dura mater in the epidural space adjacent to the subject's spinal cord to provide spinal cord stimulation therapy. In such an example, the first pair of implantable electrodes and the second pair of implantable electrodes are aligned perpendicularly along the longitudinal axis of the spinal cord to form a first circuit and a second circuit, the first circuit being positioned on the same axis as the second circuit.

[0109] Other exemplary applications exist as well, and implanted electrodes may be positioned accordingly, for example, near the spinal cord and supporting tissues (glial and microglial cells, interstitial tissue, etc.), for transforaminal stimulation of spinal nerves and spinal nerve root(s) individually or simultaneously and supporting tissues, vertebral nerves and supporting tissues, peripheral nerves and supporting tissues, and vagus nerves and supporting tissues, etc. Still other exemplary applications, including extraspinal sympathetic and parasympathetic treatments and applications, may be implemented by positioning implanted electrodes near paraspinal sites such as the cervical (including the superior cervical ganglion, middle cervical ganglion, cervicothoracic ganglion (stellate ganglion)), thoracic and lumbar regions, or prevertebral sites (e.g., the celiac ganglion, superior mesenteric ganglion, inferior mesenteric ganglion, coccygeal ganglion).

[0110] Exemplary indications and uses for electrical stimulation include pain treatment (chronic and acute), blood pressure regulation, blood glucose regulation (diabetes regulation), inflammation, heart rate and cardiac neuromodulation, respiratory neuromodulation, neuromodulation of other autonomic functions (sympathetic and parasympathetic nervous systems), and anxiety.

[0111] Thus, in the exemplary methods described herein, the methods optionally include positioning implanted electrodes in a space adjacent to neural tissue of the subject, positioning implanted electrodes in a space adjacent to vertebral nerves of the subject, positioning implanted electrodes in a space adjacent to dorsal root ganglia of the subject, positioning a first pair of implanted electrodes and a second pair of implanted electrodes in a space adjacent to the vagus nerve of the subject, or positioning implanted electrodes in a space adjacent to sympathetic and parasympathetic nerves.

[0112] In yet another example, the systems and methods described herein are useful for operating an electrical stimulator, as well as programming the electrical stimulator 100. To program the electrical stimulator 100 and select an electrode from among the implanted electrodes 108 for use, a circuit is formed (as described with reference to the methods of FIG. 13 or FIG. 14 ), and the subject can indicate where on the body the stimulation will be experienced or felt. Thus, stimulation can be shifted left / right or up / down by changing the selection of an electrode from among the implanted electrodes 108 to provide stimulation to the desired area.

[0113] The terms "about" and / or "substantially" mean that the recited property, parameter, or value need not be achieved exactly, but that deviations or variations, including, for example, tolerances, measurement errors, measurement accuracy limits, and other factors known to those skilled in the art, may occur in an amount that does not eliminate the effect the property is intended to provide.

[0114] It should be emphasized that the above-described embodiments of the present disclosure are merely possible examples of implementations, set forth for clarity of understanding. Many variations and modifications can be made to the above-described embodiments without substantially departing from the principles of the present disclosure. All such modifications and variations are intended to be included herein within the scope of the present disclosure.

Claims

1. 1. A method for electrical stimulation of a subject, comprising: forming a plurality of circuits using implantable electrodes positioned within the subject; transmitting a signal at a first frequency through a first circuit of the plurality of circuits, the first circuit generating a first electric field; transmitting a signal at a second frequency through a second circuit of the plurality of circuits, the second circuit generating a second electric field; the recessed electrodes are positioned in a substantially linear configuration along the same axis such that the first electric field and the second electric field are in an axial bias configuration; the first electric field and the second electric field interfere with each other in an overlapping region to generate a beat signal. method.

2. forming a plurality of circuits using implantable electrodes positioned within the subject, forming the first circuit between a first implanted electrode and a second implanted electrode; forming the second circuit between the first implanted electrode and a third implanted electrode; the first circuit and the second circuit have a common embedded electrode; The method of claim 1.

3. forming a plurality of circuits using implantable electrodes positioned within the subject, forming the first circuit between a first implanted electrode and a second implanted electrode; forming the second circuit between a third implanted electrode and a fourth implanted electrode; The method of claim 1 , comprising:

4. forming a plurality of circuits using implantable electrodes positioned within the subject, forming the first circuit and the second circuit using implanted electrodes on a single lead; The method of claim 1 , comprising:

5. the single lead includes a plurality of electrodes arranged in a linear electrode array; moreover, changing the selection of the first electrode of the first circuit on the single lead to change the longitudinal position of the beat signal; The method of claim 4, comprising:

6. the single lead includes a plurality of electrodes arranged in a linear electrode array; moreover, changing the configuration of the first circuit and the second circuit that are operated from among the plurality of electrodes of the linear electrode array, thereby changing the longitudinal position of the beat signal; The method of claim 4, comprising:

7. The implantable electrodes are provided on a first lead and a second lead, and forming a plurality of circuits using the implantable electrodes positioned within the subject's body comprises: forming the first circuit using the embedded electrode on the first lead; forming the second circuit using the embedded electrode on the second lead; The method of claim 1 , comprising:

8. 8. The method of claim 7, wherein the first lead and the second lead are positioned in a substantially linear configuration approximately end-to-end, and the distance between the first lead and the second lead measured perpendicular to the same axis is less than about 2 mm.

9. 10. The method of claim 1, wherein the implanted electrodes are independently controllable to be arranged as positive and negative pairs to form the first and second circuits.

10. transmitting the signal at the first frequency includes transmitting a signal at a frequency between about 1,000 Hz and about 20,000 Hz; transmitting the signal at the second frequency includes transmitting a signal at a frequency between about 1,000 Hz and about 20,000 Hz, and the first frequency is different from the second frequency; The method of claim 1.

11. The method of claim 1 , wherein the beat signal has a frequency in the range of greater than 0 Hz to about 5,000 Hz.

12. positioning the implanted electrode in space adjacent to neural tissue of the subject; The method of claim 1 further comprising:

13. positioning the implanted electrode in space adjacent to a vertebral nerve of the subject; The method of claim 1 further comprising:

14. positioning the implanted electrode in space adjacent to the subject's spinal nerves and spinal nerve roots; The method of claim 1 further comprising:

15. positioning the implanted electrode in space adjacent to a peripheral nerve of the subject; The method of claim 1 further comprising:

16. positioning the implanted electrode in a space adjacent to sympathetic and parasympathetic nerves; The method of claim 1 further comprising:

17. 1. A method for electrical stimulation of a subject, comprising: transmitting a signal at a first frequency through a first circuit formed between a first pair of implantable electrodes positioned within the subject, the first circuit generating a first electric field; transmitting a signal at a second frequency through a second circuit formed between a second pair of implantable electrodes positioned within the subject, the second circuit generating a second electric field; the first pair of implanted electrodes and the second pair of implanted electrodes are positioned in a substantially linear configuration along the same axis such that the first electric field and the second electric field are in an axial bias configuration; the first electric field and the second electric field interfere with each other in an overlapping region to generate a beat signal. method.

18. 18. The method of claim 17, wherein the first pair of implanted electrodes and the second pair of implanted electrodes are aligned vertically along a longitudinal axis of the spinal cord to form the first circuit and the second circuit, and the first circuit is positioned on the same axis as the second circuit.

19. 18. The method of claim 17, wherein the first pair of implantable electrodes and the second pair of implantable electrodes are contained on a single lead, and the first pair of implantable electrodes and the second pair of implantable electrodes are independently controllable to be arranged as a positive and negative electrode pair to form the first circuit and the second circuit.

20. The single lead includes a plurality of electrodes arranged in a linear electrode array, and the method further comprises:

20. The method of claim 19, comprising changing a longitudinal position of the beat signal by changing a selection of a first electrode of the first pair of implanted electrodes on the single lead.

21. 18. The method of claim 17, wherein the first pair of implantable electrodes is included on a first lead and the second pair of implantable electrodes is included on a second lead, and the first and second leads are positioned in the substantially linear configuration approximately end-to-end such that the distance between the first and second leads, measured perpendicular to the same axis, is less than about 2 mm.

22. 18. The method of claim 17, wherein the substantially linear configuration is approximately end-to-end and includes at least one electrode on the first lead positioned adjacent to at least one electrode on the second lead.

23. transmitting the signal at the first frequency includes transmitting a signal at a frequency between about 1,000 Hz and about 20,000 Hz; transmitting the signal at the second frequency includes transmitting a signal at a frequency between about 1,000 Hz and about 20,000 Hz, and the first frequency is different from the second frequency; 18. The method of claim 17.

24. 18. The method of claim 17, wherein the beat signal has a frequency in the range of greater than 0 Hz to about 5,000 Hz.

25. moreover, positioning the first pair of implantable electrodes in the dura mater of the epidural space adjacent to the spinal cord of the subject; positioning the second pair of implantable electrodes in the dura mater of the epidural space adjacent to the spinal cord of the subject; 18. The method of claim 17, comprising:

26. moreover, positioning the first pair of implantable electrodes and the second pair of implantable electrodes in space adjacent to neural tissue of the subject; 18. The method of claim 17, comprising:

27. moreover, positioning the first pair of implantable electrodes and the second pair of implantable electrodes in a space adjacent to a vertebral nerve of the subject; 18. The method of claim 17, comprising:

28. moreover, positioning the first pair of implantable electrodes and the second pair of implantable electrodes in a space adjacent to spinal nerves and spinal nerve roots of the subject; 18. The method of claim 17, comprising:

29. moreover, positioning the first pair of implantable electrodes and the second pair of implantable electrodes in a space adjacent to the subject's vagus nerve; 18. The method of claim 17, comprising:

30. 1. An electrical stimulation device for electrical stimulation of a subject, comprising: an interference current generator that generates an interference AC current output including a first signal and a second signal; a plurality of circuits formed using implanted electrodes, the implanted electrodes having a first end and a second end, the first end coupled to the interferential current generator and the second end configured to be positioned within the subject; the first signal is transmitted through a first circuit of the plurality of circuits to generate a first electric field; the second signal is transmitted through a second circuit of the plurality of circuits to generate a second electric field; the implanted electrodes are positioned in a substantially linear configuration along the same axis such that the first electric field of the first circuit and the second electric field of the second circuit are in an axial bias configuration; the first electric field and the second electric field interfere with each other in an overlapping region to generate a beat signal. Electrical stimulation device.

31. 31. The electrical stimulation device of claim 30, wherein the implantable electrodes include a first pair of implantable electrodes and a second pair of implantable electrodes positioned in the substantially linear configuration along the same axis.

32. 31. The electrical stimulation device of claim 30, wherein the plurality of circuits includes the first circuit between a first implantable electrode and a second implantable electrode and the second circuit between the first implantable electrode and a third implantable electrode, the first circuit and the second circuit having a common implantable electrode.

33. 31. The electrical stimulation device of claim 30, wherein the implantable electrodes are contained on a single lead, and the implantable electrodes are independently controllable to be arranged as positive and negative pairs to form the first and second circuits.

34. 31. The electrical stimulation device of claim 30, wherein the implantable electrodes are included on a first lead and a second lead, the first lead and the second lead positioned in the substantially linear configuration approximately end-to-end such that the distance between the first lead and the second lead measured perpendicular to the same axis is less than about 2 mm.

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