A system for determining a physiological characteristic of the auditory pathway in a measured patient, the system comprising: a tissue stimulation module configured to generate a plurality of electrical stimulation pulses; one or more stimulation electrodes coupled to the tissue stimulation module and configured to deliver the electrical stimulation pulses to neural tissue of the inner ear; one or more response measurement electrodes 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; characterised by a response calculation module coupled to the response measurement electrodes and receiving the tissue response signals and configured to determine a 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, and 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, wherein the response calculation module uses a local maximum and a local minimum of the one selected tissue response signal to define the calculation starting points. a tissue stimulation module configured to generate a plurality of electrical stimulation pulses; one or more stimulation electrodes coupled to the tissue stimulation module and configured to deliver the electrical stimulation pulses to neural tissue of the inner ear; one or more response measurement electrodes 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; characterised by a response calculation module coupled to the response measurement electrodes and receiving the tissue response signals and configured to determine a 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, and 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, wherein the response calculation module uses a local maximum and a local minimum of the one selected tissue response signal to define the calculation starting points. i. fitting a multi-dimensional polynomial over the plurality of tissue response signals, ii. defining calculation starting points for one selected tissue response signal, and 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, wherein the response calculation module uses a local maximum and a local minimum of the one selected tissue response signal to define the calculation starting points.