APPARATUS AND METHOD FOR OPTIMIZED STIMULATION OF A NEUROLOGICAL TARGET

• US 20110295350A1
• Filed: 07/29/2009
• Published: 12/01/2011
• 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
• Granted Patent: US 8,788,042 B2
• Time in Patent Office: Days
• US Class Current: 607/116
• 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. An apparatus for stimulating a neurological target, comprising:

at least one microelectrode positionable at the neurological target;

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

a preferred-frequency detector in communication with the impedance analyzer, the preferred-frequency detector configured to detect from among the electrical impedance values measured at each of the at least one microelectrodes, a respective preferred frequency; and

a stimulation source in communication with at least one of the at least one microelectrodes, the stimulation source configured to stimulate the neurological target at the respective preferred frequency.

2. The apparatus of claim 1, wherein each of the at least one microelectrodes is a microelectrode having dimensions approximating those of a cell, or a group of cells, of the neurological target.

3. The apparatus of claim 1, comprising a plurality of electrical microelectrodes.

4. The apparatus of claim 3, wherein the plurality of electrical microelectrodes is disposed along an elongated support structure.

5. The apparatus of claim 1, further comprising at least one electrical filter in electrical communication between the stimulation source and at least one of the at least one microelectrodes.

6. The apparatus of claim 5, wherein the at least one electrical filters is tunable to include the respective preferred frequency for the at least one of the at least one microelectrodes.

7. The apparatus of claim 6, further comprising a respective electrical filter in electrical communication between the stimulation source and each of the at least one microelectrodes.

8. The apparatus of claim 1, the stimulation source further comprises a pulse generator and an electrical filter in electrical communication between the pulse generator and at least one of the at least one microelectrodes.

9. The apparatus of claim 1, further comprising a signal router configured to selectively establish a signal path between each of the at least one microelectrodes and at least one of the impedance analyzer and the stimulation source.

10. The apparatus of claim 9, further comprising:

a sensor in communication with each of the at least one microelectrodes, the sensor configured to measure electrical signals indicative of neuronal activity; and

a controller in communication with at least the sensor and the signal router, the controller configured to selectively establish a signal path between at least one of the microelectrodes and the stimulation source responsive to electrical signals measured by the sensor.

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

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

identifying from the electrical impedance values a preferred stimulation frequency; and

stimulating the neurological target at the preferred stimulation frequency.

12. The method of claim 11, wherein the act of identifying the preferred stimulation frequency comprises determining from among the measured respective electrical impedance values, a preferred electrical impedance value having a minimum phase angle.

13. The method of claim 11, wherein the act of stimulating comprises:

receiving a broadband signal; and

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

stimulating the neurological target using the selected spectral sub-portion of the broadband signal.

14. The method of claim 13, wherein the broadband signal comprises a pulse generator signal.

15. The method of claim 13, wherein the act of selecting a sub-portion of the broadband signal comprises filtering a pulse of the pulse generator signal to a pulse width less than the inverse of the respective preferred frequency.

16. The method of claim 13, wherein the act of selecting a spectral sub-portion of the broadband signal comprises filtering the broadband signal.

17. The method of claim 11, further comprising:

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

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

18. The method of claim 11, wherein the act of stimulating the neurological target at the preferred stimulation frequency is accomplished substantially simultaneously at respective preferred stimulation frequencies for more than one of the at least one microelectrodes.

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

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

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

identifying from the electrical impedance values 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.

20. The method of claim 19, wherein the act of identifying a preferred stimulation amplitude comprises adjusting an amplitude of at least one of an electrical current and an electrical voltage responsive to the electrical impedance values.

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

measuring through each of a plurality of microelectrodes, a respective electrical impedance value indicative of the microelectrode-tissue interface impedance at each of a plurality of different frequencies;

identifying from the electrical impedance values, 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.

22. The method of claim 21, further comprising stimulating the neurological target at the preferred stimulation frequency.

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

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

means for identifying from the electrical impedance values a preferred stimulation frequency, the preferred stimulation frequency being the frequency associated with the respective impedance value closest to a pure resistance; and

means for stimulating the neurological target at the preferred stimulation frequency.