Determination of neuronal action potential amplitude based on multidimensional differential geometry

A fitting system including at least one hardware-implemented processor for fitting a cochlear implant having an implanted electrode array with a plurality of stimulation electrodes to an implanted patient based on determining a physiological characteristic of the auditory pathway in the implanted patient, the system comprising:

• a tissue stimulation module in communication with the cochlear implant via a control interface and configured to generate a plurality of electrical stimulation pulses to the one or more stimulation electrodes for delivery to auditory neural tissue of the inner ear of the implanted patient;
• one or more response measurement electrodes on the implanted electrode array configured to measure neural response over time of the auditory pathway to the electrical stimulation pulses to develop a plurality of tissue response signals, wherein each tissue response signal forms a response curve;
• and
• a response calculation module including at least one hardware-implemented processor and coupled to the response measurement electrodes to receive the tissue response signals and configured to determine the physiological characteristic by:
• i. fitting a multi-dimensional polynomial over the plurality of tissue response signals,
• ii. defining calculation starting points for one selected tissue response signal,
• iii. calculating a line of minimum principal curvature of the multi-dimensional polynomial over the plurality of tissue response signals that intersect the calculation starting points to determine the physiological characteristic of the auditory pathway, and
• iv. providing fitting instructions via the control interface to the cochlear implant based on the physiological characteristic of the auditory pathway to fit operation of the cochlear implant to the implanted patient.