Abstract
Cochlear implants (CI) are widely used in children and adults to restore hearing function. However, CI outcomes are vary widely. The affected factors have not been well understood. It is well known that the right and left hemispheres play different roles in auditory perception in adult normal hearing listeners. It is unknown how the implantation side may affect the outcomes of CIs. In this study, the effect of the implantation side on how the brain processes frequency changes within a sound was examined in 12 right-handed adult CI users. The outcomes of CIs were assessed with behaviorally measured frequency change detection threshold (FCDT), which has been reported to significantly affect CI speech performance. The brain activation and regions were also examined using acoustic change complex (ACC, a type of cortical potential evoked by acoustic changes within a stimulus), on which the waveform analysis and the standardized low-resolution brain electromagnetic tomography (sLORETA) were performed. CI users showed activation in the temporal lobe and non-temporal areas, such as the frontal lobe. Right-ear CIs could more efficiently activate the contralateral hemisphere compared to left-ear CIs. For right-ear CIs, the increased activation in the contralateral temporal lobe together with the decreased activation in the contralateral frontal lobe was correlated with good performance of frequency change detection (lower FCDTs). Such a trend was not found in left-ear CIs. These results suggest that the implantation side may significantly affect neuroplasticity patterns in adults.
Highlights
Cochlear implants (CIs) have been successful in providing auditory sensation to individuals with severe to profound hearing loss
There is a prominent difference in the amplitude and latency of acoustic change complex (ACC) N1’ between normal hearing (NH) and CI subjects
The primary findings were: (1) cortical activation patterns for the ACC-N1’ are different in right-ear CIs and left-ear CIs (Figures 1, 2); (2) Right-ear CIs could evoke stronger activities in the contralateral temporal and frontal lobes, but this contralateral hemisphere dominance was not observed for left-ear CIs (Figures 3, 4), and (3) For the right-ear CIs, the increased activation in the left temporal lobe, along with the reduced activation in the frontal lobe
Summary
Cochlear implants (CIs) have been successful in providing auditory sensation to individuals with severe to profound hearing loss. More and more CIs have been used in both children and adults with hearing loss. There is large variability in CI users’ speech outcomes. Previous studies have suggested that CI outcomes could be affected by many factors such as the duration of deafness, age at implantation, the duration of CI use, cognitive ability, and electrode placement. The underlying mechanism for the large variability in CI outcomes is still not well understood. This lack of information is a barrier to customized rehabilitation and hampers further improvement of CI outcomes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
