Children using bilateral cochlear implants (CIs) develop normal patterns of cortical activity when interimplant delays are minimized.
It is not clear whether bilateral CIs can promote normally functioning bilateral auditory pathways in children.
Cortical responses were recorded from 64 cephalic sites in 2 normal hearing participants and 8 children with 3 to 4 years of bilateral CI experience (age at first CI, 0.9-4.1 yr; age at second CI, 1.1-9.7 yr; interimplant delay, 0-5.8 yr).
Beamformer analyses on the dominant positive peak in CI users and P1 in normal hearers revealed that stimuli delivered from the left side evoked responses lateralized to right auditory cortex in the 2 participants with normal hearing and the 3 children receiving bilateral CIs with minimal interimplant delay at young ages. These 5 participants showed a shift in cortical lateralization away from the right cortical hemisphere when stimuli were moved to the right. In contrast, 4 of 5 children receiving bilateral CIs after longer delays and at older ages showed abnormal ipsilateral parietal activity in response to left stimuli and lateralization to the left cortical hemisphere in response to both right and left stimuli. The fifth child in this group showed abnormal lateralization to the ipsilateral cortex in response to both right and left stimuli.
The data suggest that, after 3 to 4 years of bilateral CI use, normal-like patterns of bilateral cortical activity are promoted in children receiving bilateral CI with minimal interimplant delays and young ages but are not present in older children who had longer interimplant delays.