Melody identification for cochlear implant users and normal hearers using expanded pitch contours

Music perception is considered unsatisfactory for most cochlear implant (CI) users. Usually, rhythm identification is adequate while pitch and melody recognition are rather limited. The aim of this study was to investigate whether insufficient contour information in the low-frequency range is one cause that contributes to the poor melody recognition results in CI users. For this purpose, the recognition of familiar melodies was tested with three differently expanded pitch contours. Ten cochlear implant subjects and five normal-hearing (NH) volunteers were investigated. Each subject chose ten out of a possible set of 23 well-known nursery songs without verbal cues. The songs were played in the original version and with three different pitch-contour expansions. All versions were tested with and without rhythm and in random order. CI subjects exhibited best results when melodies were presented with expanded pitch contours, although no clear preference for a specific contour modification was observed. Normal-hearing subjects exhibited poorer results for expanded pitch contours, especially when testing without rhythm. Both NH and CI-user groups exhibited large inter-individual differences, and melody recognition with rhythm was always better than melody recognition without rhythm. Insufficient contour information in the low-frequency range is confirmed as one contributing cause for the poor melody recognition results in CI users. Therefore, other efforts to improve low-frequency pitch discrimination, e.g., a more sophisticated design of the electrode array, a focus of the electrical stimulation pattern or an improved signal processing scheme could potentially improve melody recognition as well.