Method and device for feedback control of neural stimulation

A method of controlling a neural stimulus, the method comprising:

• applying the neural stimulus to a neural pathway in order to give rise to an evoked action potential on the neural pathway, the stimulus being defined by at least one stimulus parameter;
• measuring a neural compound action potential response evoked by the stimulus, and deriving from the measured evoked response a feedback variable;
• completing a feedback loop by using the feedback variable to control the at least one stimulus parameter value;
• and
• adaptively compensating for changes in a gain of the feedback loop caused by electrode movement relative to the neural pathway,
• wherein adaptively compensating for changes in the feedback loop comprises maintaining a corner frequency of the feedback loop at a desired value or within a desired range;
• and
• wherein the desired value or range of the corner frequency is selected to bias attenuation of heartbeat and noise while the recipient is in a more or most sensitive posture.

An implantable device for controllably applying a neural stimulus, the device comprising:

• a plurality of electrodes including one or more nominal stimulus electrodes and one or more nominal sense electrodes;
• a stimulus source for providing a stimulus to be delivered from the one or more stimulus electrodes to a neural pathway in order to give rise to an evoked action potential on the neural pathway;
• measurement circuitry for recording a neural compound action potential signal sensed at the one or more sense electrodes;
• and
• a control unit configured to:
• control application of a neural stimulus as defined by at least one stimulus parameter;
• measure via the measurement circuitry a neural compound action potential response evoked by the stimulus;
• determine from the measured evoked response a feedback variable;
• complete a feedback loop by using the feedback variable to control the at least one stimulus parameter value;
• and
• adaptively compensate for changes in a gain of the feedback loop caused by electrode movement relative to the neural pathway, by maintaining a corner frequency of the feedback loop at a desired value or within a desired range, and wherein the desired value or range of the corner frequency is selected to suitably attenuate low frequency noise such as heartbeat as well as high frequency noise such as electrical amplifier noise.

A non-transitory computer readable medium for controllably applying a neural stimulus, comprising the following instructions for execution by one or more processors:

• computer program code means for applying the neural stimulus to a neural pathway in order to give rise to an evoked action potential on the neural pathway, the stimulus being applied as defined by at least one stimulus parameter;
• computer program code means for measuring a neural compound action potential response evoked by the stimulus and deriving from the measured evoked response a feedback variable;
• computer program code means for completing a feedback loop by using the feedback variable to control the at least one stimulus parameter value;
• and
• computer program code means for adaptively compensating for changes in a gain of the feedback loop caused by electrode movement relative to the neural pathway, by maintaining a corner frequency of the feedback loop at a desired value or within a desired range, and wherein the desired value or range of the corner frequency is selected to suitably attenuate low frequency noise such as heartbeat as well as high frequency noise such as electrical amplifier noise.