[Dichotic speech recognition with cochlear implants]

Dichotic speech recognition of side-separated speech stimuli requires their central nervous processing and has been used since the 1950s in a variety of clinical settings.

The objective of this study was to investigate the dichotic speech recognition of normal-hearing (NH) subjects, cochlear implant (CI) recipients with single-sided deafness (SSD), and bilateral CI (BilCI) recipients with the dichotic discrimination test according to Feldmann.

The speech recognition of ten adult NH subjects, ten SSD CI recipients, and ten BilCI recipients was determined at 65 dB SPL or 65 dB SPL equivalent for monotic presentation of trisyllabic nouns of the Feldmann test (NH subjects: better ear, poorer ear; SSD CI recipients: NH ear, CI; BilCI recipients: better CI, poorer CI) and for dichotic, i.e., simultaneous side-separated, presentation.

The NH subjects showed significantly poorer speech recognition for dichotic presentation than for monotic presentation. Speech recognition of SSD CI recipients was significantly worse with the CI than with the NH ear for both monotic and dichotic presentation. For both presentation conditions, BilCI recipients obtained significantly lower speech recognition with the poorer CI compared to the better CI. With each of the two CI, BilCI recipients had significantly worse speech recognition for dichotic presentation than for monotic presentation.

All three study groups-NH subjects, SSD CI recipients, and BilCI recipients-were able to recognize dichotically presented speech with both ears. For SSD CI recipients, there was no negative effect of the CI on speech recognition with the NH ear for dichotic presentation.