Apparatus and method for optimized stimulation of a neurological target

• US 9,072,906 B2
• Filed: 06/26/2014
• Issued: 07/07/2015
• Est. Priority Date: 07/30/2008
• Status: Active Grant

• Current Assignee: Ecole polytechnique fãdãrale de lausanne epfl (Schweizerische Eidgenossenschaft)
• Original Assignee: Ecole polytechnique fãdãrale de lausanne epfl (Schweizerische Eidgenossenschaft)
• Inventors: Mercanzini, Andre, Renaud, Philippe
• Primary Examiner(s): Koharski, Christopher D
• Assistant Examiner(s): EDWARDS, PHILIP CHARLES
• Application Number:
  US14/316,154
• Publication Number:
  US 20140309714A1
• Time in Patent Office: 376 Days
• Field of Search: 607/45
• US Class Current: 1/1
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/24 Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
• CPC Class Codes: A61B 5/4094 Diagnosing or monitoring seizure diseases, e.g. epilepsy
• CPC Class Codes: A61N 1/0531 Brain cortex electrodes
• 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 1/36125 Details of circuitry or electric components
• CPC Class Codes: A61N 1/36171 Frequency
• CPC Class Codes: A61N 1/36185 Selection of the electrode configuration

Abstract

A preferred frequency is identified, being usable to stimulate a neurological target within a mammalian body using at least one microelectrode positioned at or near the target. To establish efficient and effective stimulation, an impedance analyzer is provided for measuring electrical impedance values indicative of a microelectrode-tissue interface across a range of different frequencies. A preferred one of the measured electrical impedance values is identified as being closest to a pure resistance. The neurological target can then be stimulated at or near the frequency associated with the preferred impedance value (peak resistance frequency), thereby promoting desirable traits, such as optimum charge transfer, minimum signal distortion, increased stimulation efficiency, and prevention of microelectrode corrosion. The peak resistance frequency can be used to determine an preferred pulse shape. A target can be identified by microelectrode measurements of neuronal activity and/or impedance magnitude at peak resistance frequency.

Claims

1. A method of stimulating a neurological target with at least one microelectrode, comprising:

receiving a broadband signal;

measuring through at least one microelectrode, respective electrical impedance values indicative of the microelectrode-tissue interface impedance at each of a plurality of different stimulation frequencies for each of the at least one microelectrodes;

identifying from the electrical impedance values measured at each of the at least one microelectrodes a preferred stimulation frequency from the plurality of different stimulation frequencies;

selecting a spectral sub-portion of the broadband signal, the spectral sub-portion including the preferred stimulation frequency; and

stimulating the neurological target at the preferred stimulation frequency using the selected spectral sub-portion of the broadband signal.

2. The method of claim 1, comprising:

determining from among the measured respective electrical impedance values, a preferred electrical impedance value having a minimum phase angle.

3. The method of claim 1, wherein the broadband signal comprises a pulse generator signal.

4. The method of claim 3, comprising:

filtering a pulse of the pulse generator signal to a pulse width less than an inverse of the respective preferred frequency.

5. The method of claim 4, comprising filtering the pulse of the pulse generator signal to the pulse width of half the inverse of the respective preferred frequency.

6. The method of claim 1, comprising:

filtering the broadband signal.

7. The method of claim 1, comprising:

measuring electrical signals indicative of neuronal activity at each of the at least one microelectrodes; and

establishing, responsive to the measured electrical signals, a signal path between at least one of the microelectrodes and a stimulation source.

8. The method of claim 1, comprising stimulating with two or more of the at least one microelectrodes.

9. The method claim 1, comprising:

identifying from the electrical impedance values measured at each of the at least one microelectrodes a preferred stimulation amplitude at the preferred stimulation frequency for each of the at least one microelectrodes; and

stimulating the neurological target at the preferred stimulation frequency and at the preferred stimulation amplitude.

10. The method of claim 9, comprising:

adjusting an amplitude of at least one of an electrical current and an electrical voltage responsive to the electrical impedance values.

11. The method of claim 1, comprising:

identifying, from the electrical impedance values measured at each of the at least one microelectrodes, a peak resistance frequency for each of a plurality of microelectrodes; and

identifying, from the respective peak resistance frequencies, one or more of the microelectrodes positioned at the neurological target.

12. An apparatus for stimulating a neurological target, comprising:

an impedance analyzer in electrical communication with at least one microelectrode to measure respective electrical impedance values indicative of the microelectrode-tissue interface at each of a plurality of different stimulation frequencies for each of the at least one microelectrodes;

a preferred-frequency detector in electrical communication with the impedance analyzer to identify, from the electrical impedance values measured at each of the at least one microelectrodes, a preferred stimulation frequency from the plurality of different stimulation frequencies, and to select a spectral sub-portion of a broadband signal, the spectral sub-portion including the preferred stimulation frequency; and

a stimulation source in electrical communication with the at least one microelectrode to stimulate the neurological target at the preferred stimulation frequency using the selected spectral sub-portion of the broadband signal.

13. The apparatus of claim 12, comprising:

the preferred-frequency detector configured to identify the preferred stimulation frequency responsive to an impedance value closest to a pure resistance from among the measured respective electrical impedance values.

14. The apparatus of claim 12, comprising:

at least one electrical filter in electrical communication between the stimulation source and at least one of the at least one microelectrodes.

15. The apparatus of claim 12, comprising:

a pulse generator.

16. The apparatus of claim 12, comprising:

a signal router configured to selectively establish a signal path between each of the at least one microelectrodes and the stimulation source.

17. The apparatus of claim 12, comprising:

a sensor in communication with each of at least one microelectrodes to measure electrical signals indicative of neuronal activity.

18. The apparatus of claim 12, comprising:

the impedance analyzer configured to identify, from the electrical impedance values measured at each of the at least one microelectrodes, a preferred stimulation amplitude at the preferred stimulation frequency for each of the at least one microelectrodes.

19. The apparatus of claim 12, comprising:

the impedance analyzer configured to adjust an amplitude of at least one of an electrical current and an electrical voltage responsive to the electrical impedance values.

20. The apparatus of claim 12, comprising:

the impedance analyzer configured to;

identify, from the electrical impedance values measured at each of the at least one microelectrodes, a peak resistance frequency for each of a plurality of microelectrodes; and

to

identify, from the respective peak resistance frequencies, one or more of the microelectrodes positioned at the neurological target.