Early improvements in phonological processing and speech recognition in adult cochlear implant users

The Nonword Repetition Test (NWRT) measures phonological processing and engages cognitive and linguistic mechanisms influencing speech recognition. This study examined early changes in phonological processing among adult cochlear implant (CI) users by comparing their pre-CI and 1-month post-CI NWRT scores. Consonant-Nucleus-Consonant (CNC) word recognition and AzBio sentence recognition scores were also included to assess early speech recognition improvements and relationships with NWRT. Additionally, to evaluate the potential mechanisms, working memory and spectrotemporal processing were assessed using digit span tasks and the Spectral-Temporally Modulated Ripple Test (SMRT), respectively. Seventeen adults aged between 50–83 years with bilateral post-lingual hearing loss completed the tasks in quiet and in best-aided conditions. Significant improvements were observed in NWRT, CNC, AzBio scores within 1 month following implantation. NWRT performance was strongly correlated with speech recognition performance at both the pre-CI and 1-month post CI time points. SMRT and Digit span scores did not show significant change and were not correlated with NWRT, although SMRT showed a positive trend. Preliminary findings may suggest that increased audibility after cochlear implantation, allows rapid improvement in phonological processing skills and speech recognition by engaging pre-existing phonological and linguistic mechanisms, even without significant changes in other auditory and cognitive functions.