title: Cortical function in children receiving bilateral cochlear implants simultaneously or after a period of interimplant delay.
abstract: OBJECTIVE
  Children using bilateral cochlear implants (CIs) develop normal patterns of cortical activity when interimplant delays are minimized.
  
  
  BACKGROUND
  It is not clear whether bilateral CIs can promote normally functioning bilateral auditory pathways in children.
  
  
  METHODS
  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).
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Archie's Cochlear Implant Laboratory, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada. karen.gordon@utoronto.ca
authors.forename: Karen A
authors.initials: KA
authors.lastname: Gordon
authors.forename: Daniel D E
authors.initials: DD
authors.lastname: Wong
authors.forename: Blake C
authors.initials: BC
authors.lastname: Papsin
mesh_terms: D001931:Brain Mapping; D002540:Cerebral Cortex / Q000503:physiopathology*; D002648:Child; D002675:Child, Preschool; D019929:Cochlear Implantation; D003054:Cochlear Implants; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology*; D006312:Hearing Loss, Bilateral / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007223:Infant; D013997:Time Factors