Investigating perceptual features of electrode stimulation via a multidimensional scaling paradigm

To achieve the most effective speech processing for individuals with cochlear implants, it is important to understand the perceptual features associated with the stimulation parameters. In general, when electrodes are stimulated in order from apex to base, the pitch of the perceived sound changes in an orderly fashion from low to high. Some deviations from this assumed order have been documented. Also, pitch is the dominant perceptual attribute of a sound when the stimuli associated with different electrodes have been accurately loudness balanced. In this study, the results of a multidimensional scaling (MDS) paradigm were compared to the results of a pitch-ranking procedure for six subjects implanted with multichannel cochlear prostheses. Results indicate that there may be multiple percepts that change with electrode location. Not surprisingly, the dominant percept is strongly correlated with pitch. The results also indicate that the structure of the second percept is consistent across subjects, although not interpretable using the data measured in this study. Furthermore, results indicate that MDS data can be used to pinpoint indiscriminable electrodes more accurately than pitch data. The results of this study may have importance for the design of the next generation of speech processors.