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. 2020 Mar:208:116455.
doi: 10.1016/j.neuroimage.2019.116455. Epub 2019 Dec 10.

Interhemispheric auditory connectivity requires normal access to sound in both ears during development

Daniel A Smieja  1 , Benjamin T Dunkley  2 , Blake C Papsin  3 , Vijayalakshmi Easwar  4 , Hiroshi Yamazaki  4 , Michael Deighton  4 , Karen A Gordon  5
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Free article

Interhemispheric auditory connectivity requires normal access to sound in both ears during development

Daniel A Smieja et al. Neuroimage. 2020 Mar.
Free article

Abstract

Despite early bilateral cochlear implantation, children with congenital deafness do not develop accurate spatial hearing; we thus asked whether auditory brain networks are disrupted in these children. EEG responses were evoked unilaterally and bilaterally in 13 children with normal hearing and 16 children receiving bilateral cochlear implants simultaneously. Active cortical areas were estimated by the Time Restricted Artifact and Coherent source Suppression (TRACS) beamformer and connected cortical areas were identified by measuring coherence between source responses. A whole-brain analysis of theta band coherence revealed the strongest connections between the temporal areas in all conditions at early latencies. Stronger imaginary coherence in activity between the two auditory cortices to bilateral than unilateral input was found in children with normal hearing reflecting facilitation in the auditory network during bilateral hearing. The opposite effect, depressed coherence, was found during bilateral stimulation in children using cochlear implants. Children with cochlear implants also showed a unique auditory network in response to bilateral stimulation which was marked by increased connectivity between occipital and frontal areas. These findings suggest that cortical networks for sound processing are normally facilitated by bilateral input but are disrupted in children who hear through two independent cochlear implants. Efforts to improve hearing in children with congenital deafness must thus include corrections to potential mismatches in bilateral input to support brain development.

Keywords: Auditory pathways; Binaural hearing; EEG; Functional connectivity; Sensorineural hearing loss.

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Conflict of interest statement

Declaration of competing interest KG is employed by the Hospital for Sick Children where she holds the Cochlear Americas Chair in Auditory Development. She has received travel support for conference attendance from Cochlear Corp, and Advanced Bionics; has consulted for the Government of Canada, CoastGuard, and been a lecturer at Salus University. BP is Otolaryngologist-in-Chief at The Hospital for Sick Children where he holds the Jordan and Lisa Gnat Family and Bastable-Potts Chair in Otolaryngology. He has received travel support for conference attendance from Cochlear Corp. and been a lecturer at Salus University. DS, BD, VE, MD, and HY declare no competing interests.

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