SYSTEMS AND METHODS FOR MONITORING NEUTRAL ACTIVITY

1 . A method, comprising:

a. applying a plurality of electrical stimuli having differing amplitudes at a first position in a brain of a patient;

b. for each of the plurality of electrical stimuli, detecting a resonant response from a target neural structure in the brain, each resonant response evoked by a respective one of the electrical stimuli;

c. determining a change in one or more common waveform characteristics between two or more of the detected resonant responses; and

d. determining an effectiveness of delivering therapeutic stimulation at the first position based on the change.

2 . The method of claim 1 , wherein the one or more common waveform characteristics comprises one or more of the following:

a) an amplitude of the resonant response;

b) a resurgence of the resonant response;

c) a frequency or change in frequency of the resonant response;

d) a temporal envelope of the resonant response;

e) a fine structure of the resonant response;

f) a rate of decay of the resonant response;

g) a delay between the onset of the stimulus and the onset of a temporal feature of the resonant response amplitude.

3 . The method of claim 1 , further comprising:

selecting an amplitude of the differing amplitudes for therapeutic stimulation of the target neural structure based on the change.

4 . The method of claim 1 , further comprising:

selecting the first position for therapeutic stimulation of the target neural structure based on the change.

5 . The method of claim 1 , further comprising:

repeating a-d at a second position in the brain different from the first position;

comparing the changes in the one or more common waveform characteristics between the first and second positions.

6 . The method of claim 5 , further comprising selecting one of the first position and the second position for therapeutic stimulation of target neural structure based on the comparison.

7 . The method of claim 6 , further comprising applying a therapeutic stimulus to the target neural structure at the selected position.

8 . The method of claim 5 , wherein the plurality of electrical stimuli applied at the first position are applied by a first electrode of a plurality of electrodes.

9 . The method of claim 7 , further comprising:

moving the first electrode between the first position and the second position in the brain; and

determining an optimum electrode position for therapeutic stimulation of target neural structure based on the comparison.

10 . The method of claim 8 , wherein the plurality of electrical stimuli applied at the second position are applied by a second electrode of the plurality of electrodes.

11 . The method of claim 1 , wherein the plurality of electrical stimuli applied at the first position are applied at the first position by two or more electrodes.

12 . The method of claim 11 , wherein at least one of the two or more electrodes is not located at the first position.

13 . The method of claim 1 , wherein the resonant response is detected at two or more electrodes.

14 . The method of claim 1 , wherein the patient is under general anaesthetic.

15 . The method of claim 1 , wherein determining the change in the one or more common waveform characteristics between the two or more of the detected resonant responses comprises determining a rate of change in the one or more of the common waveform characteristics between the two or more of the detected resonant responses.

16 . A neurostimulation system, comprising:

at least one electrode adapted for implantation in or near a target neural structure in the brain;

a signal generator selectively coupled to one or more of the at least one electrode and configured to apply a plurality of electrical stimuli having differing amplitudes via the at least one electrode at a first position in a brain of a patient;

a measurement device selectively coupled to one or more of the at least one electrode and configured to detect a resonant response from the target neural structure evoked by each of the plurality of electrical stimuli; and

a processing unit coupled to the measurement device and configured to:

determine a change in one or more common waveform characteristics between two or more of the detected resonant responses; and

determine an effectiveness of delivering therapeutic stimulation at the first position based on the change.

17 . The system of claim 16 , wherein the one or more common waveform characteristics comprises one or more of the following:

a) an amplitude of the resonant response;

b) a resurgence of the resonant response;

c) a frequency of the resonant response;

d) a temporal envelope of the resonant response;

e) a fine structure of the resonant response;

f) a rate of decay of the resonant response;

g) a delay between the onset of the stimulus and the onset of a temporal feature of the resonant response amplitude.

18 . The system of claim 16 , wherein the processing unit is further configured to:

select an amplitude of the differing amplitudes for therapeutic stimulation of the target neural structure based on the change.

19 . The system of claim 16 , wherein the processing unit is further configured to:

select the first position for therapeutic stimulation of the target neural structure based on the change.

20 . The system of claim 16 , wherein:

the at least one electrode comprises a first electrode at the first position and a second electrode at a second position different from the first position;

the signal generator is configured to apply the plurality of electrical stimuli to each of the first and second electrodes;

the measurement device is configured to detect the resonant response from the target neural structure evoked by the plurality of electrical stimuli applied to each of the first and second electrodes; and

the processing unit is configured to:

determine a change in one or more common waveform characteristics between two or more of the detected resonant responses evoked by each of the plurality of electrical stimuli applied to the second electrode in the second position;

compare the change in the one or more common waveform characteristics of the two or more of the detected resonant responses at the first electrode to a change in one or more common waveform characteristics between two or more of the detected resonant responses at the second electrode; and

select one of the first electrode and the second electrode for therapeutic stimulation of target neural structure based on the comparison.

21 . The system of claim 20 , wherein the signal generator is further configured to apply a therapeutic stimulus to the target neural structure via the selected electrode.

22 . The system of claim 16 ,

wherein the plurality of electrical stimuli are applied to a first electrode of the at least one electrode;

wherein in response to moving of the first electrode to a second position in the brain different from the first position, the signal generator is configured to apply the plurality of electrical stimuli to the first electrode in the second position;

wherein the measurement device is configured to detect the resonant response from the target neural structure evoked by each of the plurality of electrical stimuli applied to the first electrode in the second position; and

wherein the processing unit is configured to:

determine a change in one or more common waveform characteristics between two or more of the detected resonant responses evoked by each of the plurality of electrical stimuli applied to the first electrode in the second position;

compare the change in the one or more common waveform characteristics between the two or more of the detected resonant responses detected at the first position to a change in the one or more common waveform characteristics between the two or more of the detected resonant responses detected at second position; and

determine an optimum electrode position for therapeutic stimulation of target neural structure based on the comparison.

23 . The system of claim 16 , wherein determining the change in the one or more common waveform characteristics between the two or more of the detected resonant responses comprises determining a rate of change in the one or more of the common waveform characteristics between the two or more of the detected resonant responses.

24 . The system of claim 16 , wherein the plurality of electrical stimuli are applied at the first position by two or more electrodes of the at least one electrode.

25 . The system of claim 24 , wherein at least one of the two or more electrodes is not located at the first position.

26 . The system of claim 16 , wherein the resonant response is detected at two or more of the at least one electrode.