STIMULATION ELECTRODE SELECTION

• US 20110144715A1
• Filed: 12/16/2009
• Published: 06/16/2011
• Est. Priority Date: 12/16/2009
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Molnar, Gabriela C., Wu, Jianping
• Granted Patent: US 8,532,757 B2
• Time in Patent Office: Days
• US Class Current: 607/45
• CPC Class Codes: A61N 1/0534 Electrodes for deep brain stimulation
• CPC Class Codes: A61N 1/36082 Cognitive or psychiatric applications, e.g. dementia or Alzheimer's disease
• CPC Class Codes: A61N 1/36185 Selection of the electrode configuration
• CPC Class Codes: A61N 1/372 Arrangements in connection with the implantation of stimulators

Abstract

Bioelectrical signals may be sensed within a brain of a patient with a plurality of sense electrode combinations. A stimulation electrode combination for delivering stimulation to the patient to manage a patient condition can be selected based on a frequency domain characteristic of the sensed bioelectrical signals. In some examples, a stimulation electrode combination is selected based on a determination of which of the sense electrodes are located closest to a target tissue site, as indicated by the one or more sense electrodes that sensed a bioelectrical brain signal with a relatively highest value of the frequency domain characteristic. In some examples, determining which of the sense electrodes are located closest to the target tissue site may include executing an algorithm using relative values of the frequency domain characteristic.

Claims

1. A method comprising:

determining a frequency domain characteristic for each bioelectrical brain signal of a plurality of bioelectrical signals sensed in a brain of a patient with a respective electrode;

determining a plurality of relative values of the frequency domain characteristic, wherein each of the plurality of relative values is based on at least two of the frequency domain characteristics; and

selecting at least one of the electrodes for delivering stimulation to the patient based on the plurality of relative values.

2. The method of claim 1, wherein the frequency domain characteristic comprises a power level of the respective bioelectrical signal in a selected frequency band.

3. The method of claim 2, wherein the selected frequency band comprises at least one of a beta band or a gamma band.

4. The method of claim 1, wherein selecting at least one of the electrodes for delivering stimulation to the patient based on the plurality of relative values comprises:

determining a greatest relative value of the frequency domain characteristic; and

selecting the electrodes for delivering stimulation to the patient based on the electrodes with which the bioelectrical signals comprising the greatest relative value of the frequency domain characteristic were sensed.

5. The method of claim 4, wherein selecting the electrodes for delivering stimulation to the patient based on the electrodes with which the bioelectrical signals comprising the greatest relative value of the frequency domain characteristic were sensed comprises selecting the electrodes with which the bioelectrical signals comprising the greatest relative value of the frequency domain characteristic were sensed as the electrodes for delivering stimulation.

6. The method of claim 1, wherein sensing a plurality of bioelectrical signals in a brain of a patient with a plurality of electrodes comprises sensing the plurality of bioelectrical signals with a plurality of unipolar electrode combinations.

7. The method of claim 6, wherein determining the plurality of relative values of the frequency domain characteristic comprises determining a magnitude of a difference in the frequency domain characteristics of at least two bioelectrical signals.

8. The method of claim 1, wherein sensing a plurality of bioelectrical signals in a brain of a patient with a plurality of electrodes comprises sensing the plurality of bioelectrical signals with a plurality of bipolar electrode combinations.

9. The method of claim 8, wherein the frequency domain characteristic of each bioelectrical signal indicates the relative values.

10. The method of claim 1, further comprising, prior to selecting at least one of the electrodes for delivering stimulation to the patient, determining whether a target tissue site is positioned between two electrodes of the plurality of electrodes based on the relative values.

11. The method of claim 1, further comprising sensing the plurality of bioelectrical signals with at least one respective electrode of a plurality of electrodes, the bioelectrical signals comprising a first set of bioelectrical signals, wherein at least three electrodes of the plurality of electrodes comprise a common position along a longitudinal axis of a lead, the method further comprising:

sensing a second set of bioelectrical signals within the brain of the patient with at least one electrode of the at least three electrodes;

determining a frequency domain characteristic for each of the bioelectrical signals of the second set of bioelectrical signals; and

selecting one of the electrodes of the at least three electrodes for delivering stimulation to the patient based on the frequency domain characteristics of the bioelectrical signals of the second set of bioelectrical signals.

12. A method comprising:

sensing a first group of bioelectrical signals in a brain of a patient with a first group of electrodes;

sensing a second group of bioelectrical signals in the brain of the patient with a second group of electrodes;

sensing a third group of bioelectrical signals in the brain of the patient with a third group of electrodes;

sensing a fourth group of bioelectrical signals in the brain of the patient with a fourth group of electrodes;

determining a frequency domain characteristic for each of the bioelectrical signals within each of the first, second, third, and fourth groups of bioelectrical signals;

determining a first relative value of the frequency domain characteristic based on the frequency domain characteristics of the first and second groups of bioelectrical signals;

determining a second relative value of the frequency domain characteristic based on the frequency domain characteristics of the second and third groups of bioelectrical signals;

determining a third relative value of the frequency domain characteristic based on the frequency domain characteristics of the third and fourth groups of bioelectrical signals;

determining a fourth relative value of the frequency domain characteristic based on the frequency domain characteristics of the first and fourth groups of bioelectrical signals; and

selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes for delivering stimulation to a target tissue site of the patient based on the first, second, third, and fourth relative values.

13. The method of claim 12, wherein the first group of electrodes is located at a first position along a longitudinal axis of a lead, the second group of electrodes is located at a second position proximal to the first position along the longitudinal axis of the lead, the third group of electrodes is located at a third position proximal to the second position along the longitudinal axis of the lead, and the fourth group of electrodes is located at a fourth position proximal to the third position along the longitudinal axis of the lead.

14. The method of claim 12, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes for delivering stimulation to a target stimulation site of the patient based on the first, second, third, and fourth relative values comprises determining whether at least one of the first, second, third, or fourth groups of electrodes is closest to the target tissue site based on the first, second, third, and fourth relative values.

15. The method of claim 12, wherein each of the first, second, third, and fourth groups of electrodes comprises at least one individual electrode, the method further comprising selecting at least one individual electrode for delivering stimulation based on the first, second, third, and fourth relative values.

16. The method of claim 12, wherein, if the fourth relative value is greater than the first, second, and third relative values, the method further comprises:

determining whether the first relative value is greater than the second relative value; and

determining whether the second relative value is greater than the third relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the first group of electrodes if the first relative value is greater than the second relative value and the second relative value is greater than the third relative value.

17. The method of claim 12, wherein, if the fourth relative value is greater than the first, second, and third relative values, the method further comprises:

determining whether the first relative value is less than the second relative value and

determining whether the second relative value is less than the third relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the fourth group of electrodes if the first relative value is less than the second relative value and the second relative value is less than the third relative value.

18. The method of claim 12, wherein, if the fourth relative value is greater than the first, second, and third relative values and if the first relative value is not greater than the second relative value and the second relative value is not greater than the third relative value, and if the first relative value is not less than the second relative value and the second relative value is not less than the third relative value, the method further comprises determining whether the first relative value is less than the third relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from at least one of the first or second group of electrodes if the first relative value is less than the third relative value.

19. The method of claim 12, wherein, if the fourth relative value is greater than the first, second, and third relative values, and if the first relative value is not greater than the second relative value and the second relative value is not greater than the third relative value, and if the first relative value is not less than the second relative value and the second relative value is not less than the third relative value, the method further comprises determining whether the first relative value is greater than the third relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one of the third or fourth electrodes if the first relative value is greater than the third relative value.

20. The method of claim 12, wherein, if the fourth relative value is less than the first, second, and third relative values, the method further comprises determining whether the fourth relative value substantially equals zero, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from at least one of the first or fourth group of electrodes if the fourth relative value substantially equals zero.

21. The method of claim 12, wherein, if the fourth relative value is less than the first, second, and third relative values, the method further comprises determining whether the second relative value is greater than the third relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the second group of electrodes if the second relative value is greater than the third relative value.

22. The method of claim 12, wherein, if the fourth relative value is less than the first, second, and third relative values, and if the fourth relative value does not equal zero, and if the second relative value is not greater than the third relative value, the method further comprises determining whether the third relative value is greater than the second relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the third group of electrodes if the third relative value is greater than the second relative value.

23. The method of claim 12, wherein, if the second relative value is greater than the first, third, and fourth relative values, the method further comprises determining whether the first relative value is greater than the third relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the second group of electrodes if the first relative value is greater than the third relative value.

24. The method of claim 12, wherein, if the second relative value is greater than the first, third, and fourth relative values, the method further comprises determining whether the first relative value is less than the third relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the third group of electrodes if the first relative value is less than the third relative value.

25. The method of claim 12, wherein the first group of bioelectrical signals comprises a first bioelectrical signal and the first group of electrodes comprises a first electrode, the second group of bioelectrical signals comprises a second bioelectrical signal and the second group of electrodes comprises a second electrode, the third group of bioelectrical signals comprises a third bioelectrical signal and the third group of electrodes comprises a third electrode, and the fourth group of bioelectrical signals comprises a fourth bioelectrical signal and the fourth group of electrodes comprises a fourth electrode.

26. The method of claim 25, wherein, if the fourth relative value is greater than the first, second, and third relative values, the method further comprises at least one of:

determining whether the first relative value is greater than the second relative value, and determining whether the second relative value is greater than the third relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting the first electrode if the first relative value is greater than the second relative value and the second relative value is greater than the third relative value,

determining whether the first relative value is less than the second relative value and determining whether the second relative value is less than the third relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting the fourth electrode if the first relative value is less than the second relative value and the second relative value is less than the third relative value,

determining whether the first relative value is not greater than the second relative value and the second relative value is not greater than the third relative value, and if the first relative value is not less than the second relative value and the second relative value is not less than the third relative value, the method further comprises determining whether the first relative value is less than the third relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one of the first or second electrodes if the first relative value is less than the third relative value,

determining whether the first relative value is not greater than the second relative value and the second relative value is not greater than the third relative value, and if the first relative value is not less than the second relative value and the second relative value is not less than the third relative value, the method further comprises determining whether the first relative value is greater than the third relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one of the third or fourth electrodes if the first relative value is greater than the third relative value/

27. The method of claim 25, wherein, if the fourth relative value is less than the first, second, and third relative values, the method further comprises at least one of:

determining whether the fourth relative value substantially equals zero, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one of the first or fourth electrodes if the fourth relative value substantially equals zero,

determining whether the second relative value is greater than the third relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting the second electrode if the second relative value is greater than the third relative value, or

determining whether the fourth relative value does not equal zero, and if the second relative value is not greater than the third relative value, the method further comprises determining whether the third relative value is greater than the second relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting the third electrode if the third relative value is greater than the second relative value.

28. The method of claim 25, wherein, if the second relative value is greater than the first, third, and fourth relative values, the method further comprises at least one of:

determining whether the first relative value is greater than the third relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting the second electrode if the first relative value is greater than the third relative value, or

determining whether the first relative value is less than the third relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting the third electrode if the first relative value is less than the third relative value.

29. The method of claim 12, wherein:

the first group of bioelectrical signals comprises a first bioelectrical signal and the first group of electrodes comprises a first electrode,

the second group of bioelectrical signals comprises a second bioelectrical signal, a third bioelectrical signal, and a fourth bioelectrical signal and the second group of electrodes comprises a second electrode, a third electrode, and a fourth electrode,

the third group of bioelectrical signals comprises a fifth bioelectrical signal, a sixth bioelectrical signal, and a seventh bioelectrical signal and the third group of electrodes comprises a fifth electrode, a sixth electrode, and a seventh electrode, and

the fourth group of bioelectrical signals comprises an eighth bioelectrical signal and the fourth group of electrodes comprises an eighth electrode.

30. The method of claim 29, wherein determining a first relative value of the frequency domain characteristic based on the frequency domain characteristics for the first and second groups of bioelectrical signals comprises:

determining a fifth relative value of the frequency domain characteristic based on the frequency domain characteristics for the first and second bioelectrical signals;

determining a sixth relative value of the frequency domain characteristic based on the frequency domain characteristics for the first and third bioelectrical signals;

determining a seventh relative value of the frequency domain characteristic based on the frequency domain characteristics for the first and fourth bioelectrical signals;

determining a first average value based on the fifth, sixth, and seventh relative values, wherein the first relative value comprises the first average value,

wherein determining a second relative value of the frequency domain characteristic based on the frequency domain characteristics for the second and third groups of bioelectrical signals comprises;

determining an eighth relative value of the frequency domain characteristic based on the frequency domain characteristics for the second and fifth bioelectrical signals;

determining a ninth relative value of the frequency domain characteristic based on the frequency domain characteristics for the third and sixth bioelectrical signals;

determining a tenth relative value of the frequency domain characteristic based on the frequency domain characteristics for the fourth and seventh bioelectrical signals; and

determining a second average value based on the eighth, ninth, and tenth relative values, wherein the second relative value comprises the second average value,

wherein determining a third relative value of the frequency domain characteristic based on the frequency domain characteristics for the third and fourth groups of bioelectrical signals comprises;

determining an eleventh relative value of the frequency domain characteristic based on the frequency domain characteristics for the fifth and eighth bioelectrical signals;

determining a twelfth relative value of the frequency domain characteristic based on the frequency domain characteristics for the sixth and eighth bioelectrical signals;

determining a thirteenth relative value of the frequency domain characteristic based on the frequency domain characteristics for the seventh and eighth bioelectrical signals; and

determining a third average value based on the eleventh, twelfth, and thirteenth relative values, wherein the third relative value comprises the third average value, and

wherein determining a fourth relative value of the frequency domain characteristic based on the frequency domain characteristics for the first and fourth groups of bioelectrical signals comprises determining a fourteenth relative value of the frequency domain characteristic based on the frequency domain characteristics for the first and eighth bioelectrical signals, wherein the fourth relative value comprises the fourteenth relative value.

31. The method of claim 29, wherein, if the fourth relative value is greater than the first, second, and third relative values, the method further comprises at least one of:

determining whether the first relative value is greater than the second relative value, and determining whether the second relative value is greater than the third relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting the first electrode if the first relative value is greater than the second relative value and the second relative value is greater than the third relative value,

determining whether the first relative value is less than the second relative value, and determining whether the second relative value is less than the third relative value, wherein selecting at least one of the first, second, third, or fourth groups of electrodes comprises selecting the eighth electrode if the first relative value is less than the second relative value and the second relative value is less than the third relative value,

determining whether the first relative value is not greater than the second relative value and the second relative value is not greater than the third relative value, and if the first relative value is not less than the second relative value and the second relative value is not less than the third relative value, the method further comprises determining whether the first relative value is less than the third relative value, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from at least one of the first or second groups of electrodes if the first relative value is less than the third relative value, or

determining whether the first relative value is not greater than the second relative value and the second relative value is not greater than the third relative value, and if the first relative value is not less than the second relative value and the second relative value is not less than the third relative value, the method further comprises determining whether the first relative value is greater than the third relative value, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises at least one of selecting at least one electrode from the third group of electrodes or selecting the fourth electrode if the first relative value is greater than the third relative value.

32. The method of claim 29, wherein, if the fourth relative value is less than the first, second, and third relative values, the method further comprises at least one of:

determining whether the fourth relative value substantially equals zero, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one of the first or eighth electrodes if the fourth relative value substantially equals zero,

determining whether the second relative value is greater than the third relative value, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the second group of electrodes if the second relative value is greater than the third relative value, or

determining whether the fourth relative value does not equal zero, and if the second relative value is not greater than the third relative value, the method further comprises determining whether the third relative value is greater than the second relative value, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the third group of electrodes if the third relative value is greater than the second relative value.

33. The method of claim 29, wherein, if the second relative value is greater than the first, third, and fourth relative values, the method further comprises at least one of:

determining whether the first relative value is greater than the third relative value, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the second group of electrodes if the first relative value is greater than the third relative value, or

determining whether the first relative value is less than the third relative value, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the third group of electrodes if the first relative value is less than the third relative value.

34. The method of claim 29, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the second group of electrodes, the method further comprising selecting at least one of the second, third or fourth electrodes by at least:

determining a fifteenth relative value of the frequency characteristic based on the second and third bioelectrical signals;

determining a sixteenth relative value of the frequency characteristic based on the third and fourth bioelectrical signals; and

determining a seventeenth relative value of the frequency characteristic based on the fourth and second bioelectrical signals,

wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one of the second, third or fourth electrodes based on the fifteenth, sixteenth, and seventeenth relative values.

35. The method of claim 34, wherein selecting at least one of the second, third or fourth electrodes based on the fifteenth, sixteenth, and seventeenth relative values comprises:

determining whether the fifteenth relative value is substantially equal to the seventeenth relative value;

determining whether the sixteenth relative value is substantially equal to zero; and

selecting the second electrode if the fifteenth relative value is substantially equal to the seventeenth relative value and the sixteenth relative value is substantially equal to zero.

36. The method of claim 34, wherein selecting at least one of the second, third or fourth electrodes based on the fifteenth, sixteenth, and seventeenth relative values comprises:

determining whether the fifteenth relative value is substantially equal to zero;

determining whether the sixteenth relative value is less than the seventeenth relative value; and

selecting at least one of the second or third electrodes if the fifteenth relative value is substantially equal to zero and the sixteenth relative value is less than the seventeenth relative value.

37. The method of claim 29, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the third group of electrodes, the method further comprising selecting at least one of the fifth, sixth, or seventh electrodes by at least:

determining an eighteenth relative value of the frequency characteristic based on the fifth and sixth bioelectrical signals;

determining a nineteenth relative value of the frequency characteristic based on the sixth and seventh bioelectrical signals; and

determining a twentieth relative value of the frequency characteristic based on the seventh and fifth bioelectrical signals;

wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one of the fifth, sixth, or seventh electrodes based on the eighteenth, nineteenth, and twentieth relative values.

38. The method of claim 37, wherein selecting at least one of the fifth, sixth, or seventh electrodes based on the eighteenth, nineteenth, and twentieth relative values comprises:

determining whether the eighteenth relative value is substantially equal to the twentieth relative value;

determining whether the nineteenth relative value is substantially equal to zero; and

selecting the sixth electrode if the eighteenth relative value is substantially equal to the twentieth relative value and the nineteenth relative value is substantially equal to zero.

39. The method of claim 37, wherein selecting at least one of the fifth, sixth, or seventh electrodes based on the eighteenth, nineteenth, and twentieth relative values comprises:

determining whether the eighteenth relative value is substantially equal to zero;

determining whether the nineteenth relative value is less than the twentieth relative value; and

selecting at least one of the fifth or sixth electrodes if the eighteenth relative value is substantially equal to zero and the nineteenth relative value is less than the twentieth relative value.

40. The method of claim 12, wherein:

the first group of bioelectrical signals comprises a first bioelectrical signal, a second bioelectrical signal, and a third bioelectrical signal and the first group of electrodes comprises a first electrode, a second electrode, and a third electrode,

the second group of bioelectrical signals comprises a fourth bioelectrical signal, a fifth bioelectrical signal, and a sixth bioelectrical signal and the second group of electrodes comprises a fourth electrode, a fifth electrode, and a sixth electrode,

the third group of bioelectrical signals comprises a seventh bioelectrical signal, an eighth bioelectrical signal, and a ninth bioelectrical signal and the third group of electrodes comprises a seventh electrode, an eighth electrode, and a ninth electrode, and

the fourth group of bioelectrical signals comprises a tenth bioelectrical signal, an eleventh bioelectrical signal, and a twelfth bioelectrical signal and the fourth group of electrodes comprises a tenth electrode, an eleventh electrode, and a twelfth electrode.

41. The method of claim 40, wherein determining a first relative value of the frequency domain characteristic based on the frequency domain characteristics for the first and second groups of bioelectrical signals comprises:

determining a fifth relative value of the frequency domain characteristic based on the frequency domain characteristics for the first and fourth bioelectrical signals;

determining a sixth relative value of the frequency domain characteristic based on the frequency domain characteristics for the second and fifth bioelectrical signals;

determining a seventh relative value of the frequency domain characteristic based on frequency domain characteristics for the third and sixth bioelectrical signals;

determining a first average value based on the fifth, sixth, and seventh relative values, wherein the first relative value comprises the first average value,

wherein determining a second relative value of the frequency domain characteristic based on the frequency domain characteristics for the second and third groups of bioelectrical signals comprises;

determining an eighth relative value of the frequency domain characteristic based on the frequency domain characteristics for the fourth and seventh bioelectrical signals;

determining a ninth relative value of the frequency domain characteristic based on the frequency domain characteristics for the fifth and eighth bioelectrical signals;

determining a tenth relative value of the frequency domain characteristic based on the frequency domain characteristics for the sixth and ninth bioelectrical signals; and

determining a second average value based on the eighth, ninth, and tenth relative values, wherein the second relative value comprises the second average value,

wherein determining a third relative value of the frequency domain characteristic based on the frequency domain characteristics for the third and fourth groups of bioelectrical signals comprises;

determining an eleventh relative value of the frequency domain characteristic based on the frequency domain characteristics for the seventh and tenth bioelectrical signals;

determining a twelfth relative value of the frequency domain characteristic based on the frequency domain characteristics for the eighth and eleventh bioelectrical signals;

determining a thirteenth relative value of the frequency domain characteristic based on the frequency domain characteristics for the ninth and twelfth bioelectrical signals; and

determining a third average value based on the eleventh, twelfth, and thirteenth relative values, wherein the third relative value comprises the third average value, and

wherein determining a fourth relative value of the frequency domain characteristic based on the frequency domain characteristics for the first and fourth groups of bioelectrical signals comprises;

determining a fourteenth relative value of the frequency domain characteristic based on the frequency domain characteristics for the first and tenth bioelectrical signals;

determining a fifteenth relative value of the frequency domain characteristic based on the frequency domain characteristics for the second and eleventh bioelectrical signals;

determining a sixteenth relative value of the frequency domain characteristic based on the frequency domain characteristics for the third and twelfth bioelectrical signals; and

determining a fourth average value based on the fourteenth, fifteenth, and sixteenth relative values, wherein the fourth relative value comprises the fourth average value.

42. The method of claim 41, wherein, if the fourth relative value is greater than the first, second, and third relative values, the method further comprises at least one of:

determining whether the first relative value is greater than the second relative value, and determining whether the second relative value is greater than the third relative value, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the first group of electrodes if the first relative value is greater than the second relative value and the second relative value is greater than the third relative value,

determining whether the first relative value is less than the second relative value, and determining whether the second relative value is less than the third relative value, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the fourth group of electrodes if the first relative value is less than the second relative value and the second relative value is less than the third relative value,

determining whether the first relative value is not greater than the second relative value and the second relative value is not greater than the third relative value, and if the first relative value is not less than the second relative value and the second relative value is not less than the third relative value, the method further comprises determining whether the first relative value is less than the third relative value, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from at least one of the first or second groups of electrodes if the first relative value is less than the third relative value,

determining whether the first relative value is not greater than the second relative value and the second relative value is not greater than the third relative value, and if the first relative value is not less than the second relative value and the second relative value is not less than the third relative value, the method further comprises determining whether the first relative value is greater than the third relative value, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from at least one of the third or fourth groups of electrodes if the first relative value is greater than the third relative value.

43. The method of claim 41, wherein, if the fourth relative value is less than the first, second, and third relative values, the method further comprises at least one of:

determining whether the fourth relative value equals zero, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from at least one of the first or fourth groups of electrodes if the fourth relative value equals zero,

determining whether the second relative value is greater than the third relative value, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the second group of electrodes if the second relative value is greater than the third relative value,

determining whether the second relative value is not greater than the third relative value, and if the second relative value is not greater than the third relative value, the method further comprises determining whether the third relative value is greater than the second relative value, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the third group of electrodes if the third relative value is greater than the second relative value.

44. The method of claim 41, wherein, if the second relative value is greater than the first, third, and fourth relative values, the method further comprises at least one of:

determining whether the first relative value is greater than the third relative value, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the second group of electrodes if the first relative value is greater than the third relative value, or

determining whether the first relative value is less than the third relative value, wherein selecting at least one electrode from at least one of the first, second, third, or fourth groups of electrodes comprises selecting at least one electrode from the third group of electrodes if the first relative value is less than the third relative value.