STIMULATION ELECTRODE SELECTION

• US 20110144521A1
• 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 8,538,513 B2
• Time in Patent Office: Days
• US Class Current: 600/544
• CPC Class Codes: A61B 5/374 Detecting the frequency distribution of signals, e.g. detecting delta, theta, alpha, beta or gamma waves
• CPC Class Codes: A61B 5/4082 Diagnosing or monitoring movement diseases, e.g. Parkinson, Huntington or Tourette
• CPC Class Codes: A61N 1/0534 Electrodes for deep brain stimulation
• CPC Class Codes: A61N 1/36139 with automatic adjustment
• CPC Class Codes: A61N 1/36171 Frequency
• CPC Class Codes: A61N 1/36185 Selection of the electrode configuration

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 system comprising:

a plurality of electrodes;

a sensing module that senses a plurality of bioelectrical brain signals via at least one electrode of the plurality of electrodes; and

a processor that determines a frequency domain characteristic for each of the plurality of bioelectrical signals, determines 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 selects at least one of the plurality of electrodes for delivering stimulation to the patient based on the plurality of relative values.

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

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

4. The system of claim 1, wherein the processor determines a greatest relative value of the frequency domain characteristic and selects the electrodes for delivering stimulation to the patient based on the electrodes with which the sensing module sensed the bioelectrical signals comprising the greatest relative value of the frequency domain characteristic.

5. The system of claim 1, wherein the sensing module senses the plurality of bioelectrical signals with a plurality of unipolar electrode combinations.

6. The system of claim 5, wherein the processor determines a magnitude of a difference in the frequency domain characteristics of at least two bioelectrical signals in order to determine the plurality of relative values of the frequency domain characteristic.

7. The system of claim 1, wherein the sensing module senses the plurality of bioelectrical signals with a plurality of bipolar electrode combinations.

8. The system of claim 7, wherein the frequency domain characteristic of each bioelectrical signal indicates the relative values.

9. The system of claim 1, wherein the processor determines whether a target tissue site is positioned between two electrodes of the plurality of electrodes based on the relative values prior to selecting at least one of the electrodes for delivering stimulation to the patient.

10. The system of claim 1, wherein the sensing module senses the plurality of bioelectrical signals with at least one respective electrode of the 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,

wherein the sensing module senses a second set of bioelectrical signals within the brain of the patient with at least one electrode of the at least three electrodes, and

wherein the processor determines a frequency domain characteristic for each of the bioelectrical signals of the second set of bioelectrical signals and selects 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.

11. A system comprising:

a plurality of electrodes;

a sensing module that senses a first group of bioelectrical signals in a brain of a patient via a first group of electrodes comprising at least one electrode from the plurality of electrodes, a second group of bioelectrical signals in the brain of the patient via a second group of electrodes comprising at least one electrode from the plurality of electrodes, a third group of bioelectrical signals in the brain of the patient via a third group of electrodes comprising at least one electrode from the plurality of electrodes, and a fourth group of bioelectrical signals in the brain of the patient via a fourth group of electrodes comprising at least one electrode from the plurality of electrodes; and

a processor that determines a frequency domain characteristic for each of the bioelectrical signals within each of the first, second, third, and fourth groups of bioelectrical signals, determines a first relative value of the frequency domain characteristic based on the frequency domain characteristics for the first and second groups of bioelectrical signals, determines a second relative value of the frequency domain characteristic based on the frequency domain characteristics for the second and third groups of bioelectrical signals, determines a third relative value of the frequency domain characteristic based on the frequency domain characteristics for the third and fourth groups of bioelectrical signals, determines a fourth relative value of the frequency domain characteristic based on the frequency domain characteristics for the first and fourth groups of bioelectrical signals, and selects 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.

12. The system of claim 11, 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.

13. The system of claim 11, wherein the processor selects 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 based on 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.

14. The system of claim 11, wherein the processor selects at least one individual electrode for delivering stimulation based on the first, second, third, and fourth relative values.

15. The system of claim 11, wherein, if the processor determines that the fourth relative value is greater than the first, second, and third relative values, the processor determines whether the first relative value is greater than the second relative value and whether the second relative value is greater than the third relative value and selects 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.

16. The system of claim 11, wherein, if the processor determines that the fourth relative value is greater than the first, second, and third relative values, the processor determines whether the first relative value is less than the second relative value and whether the second relative value is less than the third relative value and selects 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.

17. The system of claim 11, wherein, if the processor determines that the fourth relative value is greater than the first, second, and third relative values, and that 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 that 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 processor determines whether the first relative value is less than the third relative value and selects at least one electrode from the first or second group of electrodes if the first relative value is less than the third relative value.

18. The system of claim 11, where, if the processor determines that the fourth relative value is greater than the first, second, and third relative values, and that 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 that 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 processor determines whether the first relative value is greater than the third relative value and selects at least one electrode from the third or fourth group of electrodes if the first relative value is greater than the third relative value.

19. The system of claim 11, wherein, if the processor determines that the fourth relative value is less than the first, second, and third relative values, the processor determines whether the fourth relative value substantially equals zero and selects at least one electrode from the first or fourth group of electrodes if the fourth relative value substantially equals zero.

20. The system of claim 11, wherein, if the processor determines that the fourth relative value is less than the first, second, and third relative values, the processor determines whether the second relative value is greater than the third relative value and selects at least one electrode from the second group of electrodes if the second relative value is greater than the third relative value.

21. The system of claim 11, wherein, if the processor determines that the fourth relative value is less than the first, second, and third relative values, and that the fourth relative value does not equal zero, and that the second relative value is not greater than the third relative value, the processor determines whether the third relative value is greater than the second relative value and selects at least one electrode from the third group of electrodes if the third relative value is greater than the second relative value.

22. The system of claim 11, wherein, if the processor determines that the second relative value is greater than the first, third, and fourth relative values, the processor determines whether the first relative value is greater than the third relative value and selects at least one electrode from the second group of electrodes if the first relative value is greater than the third relative value.

23. The system of claim 11, wherein, if the processor determines that the second relative value is greater than the first, third, and fourth relative values, the processor determines whether the first relative value is less than the third relative value and selects at least one electrode from the third group of electrodes if the first relative value is less than the third relative value.

24. The system of claim 11, 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.

25. The system of claim 24, wherein, if the processor determines that the fourth relative value is greater than the first, second, and third relative values, the processor at least one of:

determines whether the first relative value is greater than the second relative value and whether the second relative value is greater than the third relative value and selects 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,

determines whether the first relative value is less than the second relative value and whether the second relative value is less than the third relative value and selects 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,

determines 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 whether 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, wherein the processor determines whether the first relative value is less than the third relative value 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 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, and selects at least one of the first or second electrodes if the first relative value is less than the third relative value, or

determines 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 whether 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, wherein the processor determines whether the first relative value is greater than the third relative value 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 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, and selects at least one of the third or fourth electrodes if the first relative value is greater than the third relative value.

26. The system of claim 24, wherein if the processor determines that the fourth relative value is less than the first, second, and third relative values, the processor at least one of:

determines whether the fourth relative value substantially equals zero and selects at least one of the first or fourth electrodes if the fourth relative value substantially equals zero,

determines whether the second relative value is greater than the third relative value and selects the second electrode if the second relative value is greater than the third relative value, or

determines whether the fourth relative value does not equal zero, and that the second relative value is not greater than the third relative value, and determines whether the third relative value is greater than the second relative value if the fourth relative value does not equal zero and second relative value is not greater than the third relative value, and selects the third electrode if the third relative value is greater than the second relative value.

27. The system of claim 24, wherein if the processor determines that the second relative value is greater than the first, third, and fourth relative values, the processor determines whether the first relative value is greater than the third relative value and selects the second electrode if the first relative value is greater than the third relative value, or determines whether the first relative value is less than the third relative value and selects the third electrode if the first relative value is less than the third relative value.

28. The system of claim 11, 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.

29. The system of claim 28, wherein the processor determines the first relative value of the frequency domain characteristic based on the frequency domain characteristics for the first and second groups of bioelectrical signals by at least:

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 the processor determines the second relative value of the frequency domain characteristic based on the frequency domain characteristics for the second and third groups of bioelectrical signals by at least;

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 the processor determines the third relative value of the frequency domain characteristic based on the frequency domain characteristics for the third and fourth groups of bioelectrical signals by at least;

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 the processor determines the fourth relative value of the frequency domain characteristic based on the frequency domain characteristics for the first and fourth groups of bioelectrical signals by at least 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.

30. The system of claim 28, wherein if the processor determines that the fourth relative value is greater than the first, second, and third relative values, the processor at least one of:

determines whether the first relative value is greater than the second relative value and whether the second relative value is greater than the third relative value and selects 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,

determines whether the first relative value is less than the second relative value, and determines whether the second relative value is less than the third relative value, and selects 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,

determines 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, determines whether 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, 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 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 processor determines whether the first relative value is less than the third relative value, and selects 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

determines 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 determines whether 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, wherein the processor determines whether the first relative value is greater than the third relative value 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 selects 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.

31. The system of claim 28, wherein if the processor determines that the fourth relative value is less than the first, second, and third relative values, the processor at least one of:

determines whether the fourth relative value substantially equals zero, and selects at least one of the first or eighth electrodes if the fourth relative value substantially equals zero,

determines whether the second relative value is greater than the third relative value and selects the second electrode if the second relative value is greater than the third relative value, or

determines whether the fourth relative value does not equal zero, and that the second relative value is not greater than the third relative value, and determines whether the third relative value is greater than the second relative value if the fourth relative value does not equal zero and second relative value is not greater than the third relative value, and selects the third electrode if the third relative value is greater than the second relative value.

32. The system of claim 28, wherein, the processor determines whether the second relative value is greater than the first, third, and fourth relative values, and at least one of:

determines whether the first relative value is greater than the third relative value, and selects at least one electrode from the second group of electrodes if the first relative value is greater than the third relative value or

determines whether the first relative value is less than the third relative value, and selects at least one electrode from the third group of electrodes if the first relative value is less than the third relative value.

33. The system of claim 28, wherein the processor selects at least one electrode from the second group of 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;

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

selecting at least one of the second, third or fourth electrodes based on the fifteenth, sixteenth, and seventeenth relative values.

34. The system of claim 33, wherein the processor selects at least one of the second, third or fourth electrodes based on the fifteenth, sixteenth, and seventeenth relative values by at least:

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.

35. The system of claim 33, wherein the processor selects at least one of the second, third or fourth electrodes based on the fifteenth, sixteenth, and seventeenth relative values by at least:

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.

36. The system of claim 28, wherein the processor selects at least one electrode from the third group of 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;

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

selecting at least one of the fifth, sixth, or seventh electrodes based on the eighteenth, nineteenth, and twentieth relative values.

37. The system of claim 36, wherein the processor selects at least one of the fifth, sixth, or seventh electrodes based on the eighteenth, nineteenth, and twentieth relative values by at least:

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.

38. The system of claim 36, wherein the processor selects selecting at least one of the fifth, sixth, or seventh electrodes based on the eighteenth, nineteenth, and twentieth relative values by at least:

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.

39. The system of claim 11, 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.

40. A system comprising:

means for sensing a plurality of bioelectrical brain signals via respective electrodes;

means for determining a frequency domain characteristic for each of the plurality of bioelectrical signals;

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

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

41. The system of claim 40, wherein the means for sensing a plurality of bioelectrical brain signals via respective electrodes comprises means for sensing the plurality of bioelectrical brain signals with a plurality of unipolar electrode combinations, and wherein the means for determining a plurality of relative values of the frequency domain characteristics comprises means for determining a magnitude of a difference in the frequency domain characteristics of at least two bioelectrical signals in order to determine the plurality of relative values of the frequency domain characteristic.

42. The system of claim 40, wherein the means for sensing a plurality of bioelectrical brain signals via respective electrodes comprises means for sensing the plurality of bioelectrical brain signals with a plurality of bipolar electrode combinations, and the frequency domain characteristic of each bioelectrical brain signal indicates the relative values.

43. The system of claim 40, wherein the means for selecting at least one of the plurality of electrodes for delivering stimulation to the patient comprises means for determining whether a target tissue site is positioned between two electrodes of the plurality of electrodes based on the relative values prior to selecting at least one of the electrodes for delivering stimulation to the patient.

44. The system of claim 40, wherein the means for sensing a plurality of bioelectrical brain signals comprises means for sensing the plurality of bioelectrical brain signals with at least one respective electrode of the 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,

wherein the means for sensing a plurality of bioelectrical brain signals comprises means for sensing a second set of bioelectrical signals within the brain of the patient with at least one electrode of the at least three electrodes, and

wherein the means for selecting at least one of the plurality of electrodes for deliver stimulation to the patient comprises means for determining a frequency domain characteristic for each of the bioelectrical signals of the second set of bioelectrical signals and means for 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.

45. A system comprising:

means for sensing a first group of bioelectrical signals in a brain of a patient via a first group of electrodes comprising at least one electrode from the plurality of electrodes, a second group of bioelectrical signals in the brain of the patient via a second group of electrodes comprising at least one electrode from the plurality of electrodes, a third group of bioelectrical signals in the brain of the patient via a third group of electrodes comprising at least one electrode from the plurality of electrodes, and a fourth group of bioelectrical signals in the brain of the patient via a fourth group of electrodes comprising at least one electrode from the plurality of electrodes;

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

means for 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, a second relative value of the frequency domain characteristic based on the frequency domain characteristics for the second and third groups of bioelectrical signals, a third relative value of the frequency domain characteristic based on the frequency domain characteristics for the third and fourth groups of bioelectrical signals, a fourth relative value of the frequency domain characteristic based on the frequency domain characteristics for the first and fourth groups of bioelectrical signals; and

means for selecting an 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.

46. A computer-readable storage medium comprising instructions that cause a programmable processor to:

determine a frequency domain characteristic for each of a plurality of bioelectrical signals sensed in a brain of a patient with respective electrodes;

determine 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

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

47. A computer-readable storage medium comprising instructions that cause a programmable processor to:

determine a frequency domain characteristic each bioelectrical brain signal of a first group of bioelectrical signals in a brain of a patient with a first group of electrodes, a second group of bioelectrical signals in the brain of the patient with a second group of electrodes, a third group of bioelectrical signals in the brain of the patient with a third group of electrodes, and a fourth group of bioelectrical signals in the brain of the patient with a fourth group of electrodes;

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

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

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

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

select 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.