Institute of Medical Sciences, University of Toronto, Toronto, ON M5S 1A8, Canada; Neurosciences & Mental Health, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada.
Department of Otolaryngology - Head & Neck Surgery, University of Toronto, Toronto, ON M5G 2N2, Canada; Otolaryngology - Head & Neck Surgery, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada.
Neuroimage Clin. 2017 Nov 9;17:415-425. doi: 10.1016/j.nicl.2017.10.036. eCollection 2018.
Bilateral hearing in early development protects auditory cortices from reorganizing to prefer the better ear. Yet, such protection could be disrupted by mismatched bilateral input in children with asymmetric hearing who require electric stimulation of the auditory nerve from a cochlear implant in their deaf ear and amplified acoustic sound from a hearing aid in their better ear (bimodal hearing). Cortical responses to bimodal stimulation were measured by electroencephalography in 34 bimodal users and 16 age-matched peers with normal hearing, and compared with the same measures previously reported for 28 age-matched bilateral implant users. Both auditory cortices increasingly favoured the better ear with delay to implanting the deaf ear; the time course mirrored that occurring with delay to bilateral implantation in unilateral implant users. Preference for the implanted ear tended to occur with ongoing implant use when hearing was poor in the non-implanted ear. Speech perception deteriorated with longer deprivation and poorer access to high-frequencies. Thus, cortical preference develops in children with asymmetric hearing but can be avoided by early provision of balanced bimodal stimulation. Although electric and acoustic stimulation differ, these inputs can work sympathetically when used bilaterally given sufficient hearing in the non-implanted ear.
双侧听力在早期发育中保护听觉皮层免受重组，以偏向更好的耳朵。然而，对于需要电刺激失聪耳内的听神经和增强健耳内助听器声音的双侧输入不匹配的听力不对称儿童（双模式听力），这种保护可能会受到干扰。通过脑电图测量了 34 名双模式使用者和 16 名年龄匹配的正常听力同伴的双模式刺激的皮质反应，并与以前报告的 28 名年龄匹配的双侧植入物使用者的相同测量结果进行了比较。随着失聪耳植入时间的延迟，两个听觉皮层都越来越偏向于更好的耳朵；时间过程与单侧植入物使用者双侧植入物延迟时发生的情况相吻合。当非植入耳听力较差时，植入耳的偏好往往会随着植入物的持续使用而发生。随着剥夺时间的延长和高频听力的恶化，言语感知能力下降。因此，在听力不对称的儿童中，皮质偏好会发展，但通过早期提供平衡的双模式刺激可以避免。尽管电刺激和声音刺激不同，但在非植入耳有足够听力的情况下，双侧使用这些输入可以协同工作。
