gms | German Medical Science

The majority of Cochlear Implant (CI) users are able to discriminate the pitches of two adjacent electrode contacts. The HiRes system of Advanced Bionics offers the possibility to present additional pitches by steering current between two adjacent electrode contacts. This current steering technique generates so called “virtual channels”.

In a first study, it was shown that the subjects were able to discriminate these intermediate channels. This follow-up study evaluated whether there is a learning effect during the first six months. Virtual and physical channels were presented in pairs of pitches to the subjects and they had to decide which tone was higher.

Five adult CI users participated in this study. They used both the HiRes90K or CII implant and the HiRes speech coding strategy. They had a mean age of 47.9 years (38.3 to 61.4 years) and a mean duration of deafness of 0.7 years (0 to 2.5 years). They were all postlingually deafened.

During the first six months after implantation, a noticeable improvement of pitch resolution could be shown. This result indicates a learning effect. Directly after the first fitting, only a few participants were able to discriminate channels in a small region of the electrode array, with a resolution of 0.5 (i.e. one intermediate channel could be reached). In the next months, a few subject showed great improvement in their ability to differentiation between channels. Others showed, at least, a flat learning curve. These results show that pitch perception can be learned over time. Further improvement after more than six months is considered to be possible.