This method of determining an intracochlea tissue impedance comprises using at least two stimulating electrodes to apply an electrical stimulus to intracochlea tissue. A voltage caused by the stimulus is measured between two measuring electrodes distinct from the stimulating electrodes. From the voltage a stimulus-response characteristic of tissue between the two measuring electrodes is determined. This allows the tissue/electrode interface impedance and potential and the tissue impedance and potential to be uniquely determined. In turn, modiolus currents can be estimated in monopolar stimulation mode. Also provided is automated initiation of re-mapping of the device when tissue characteristics change.
