Current distributions in the cat cochlea: a modelling and electrophysiological study

The current distribution of bipolar electrodes implanted into the scala tympani of the cat cochlea was investigated using a two-electrode masking technique. Two electrode masking is a non-invasive technique which requires two electrically independent electrodes and relies upon the forward masking of the electrically evoked brainstem response to a probe stimulus by that of a preceding test stimulus. The technique was described in terms of a model, which enabled an approach for estimating the scala tympani length constant to be established. Model results have shown good agreement with electrophysiological results. Application of the model confirmed the scala tympani length constant within the basal turn of the cochlea to lie between 3 and 4 mm.