Neural alpha oscillations and auditory steady-state responses during adaptation to a cochlear implant

The human auditory system must distinguish relevant sounds from noise. Severe hearing loss can be treated with cochlear implants (CIs), but how the brain adapts to electrical hearing remains unclear. This study examined adaptation to unilateral CI use in the first and seventh months after CI activation using speech comprehension measures and electroencephalography recordings, both during passive listening and an active spatial listening task. Neural phase-locking to amplitude-modulated sounds interacted with time, such that phase-locking longitudinally increased stronger for 40 Hz compared with 4 Hz. In the spatial listening task, the benefit of performing the task with the CI on vs. off was most pronounced when the CI ear was primarily exposed to target speech. Lateralized alpha oscillations (~10 Hz) reliably marked CI users' focus of spatial attention. Stronger alpha modulation in the hemisphere opposite to the nonimplanted ear indicates an attentional bias toward the acoustically hearing ear. Our findings suggest that adaptation to hearing with a CI is accomplished by dynamic changes in auditory phase locking and a bias in auditory spatial attention.