Differential auditory cortical development in left and right cochlear implanted children

Abstract

Unilateral aural stimulation has been shown to cause massive cortical reorganization in brain with congenital deafness, particularly during the sensitive period of brain development. However, it is unclear which side of stimulation provides most advantages for auditory development. The left hemisphere dominance of speech and linguistic processing in normal hearing adult brain has led to the assumption of functional and developmental advantages of right over left implantation, but existing evidence is controversial. To test this assumption and provide evidence for clinical choice, we examined 34 prelingually deaf children with unilateral cochlear implants using near-infrared spectroscopy. While controlling for age of implantation, residual hearing, and dominant hand, cortical processing of speech showed neither developmental progress nor influence of implantation side weeks to months after implant activation. In sharp contrast, for nonspeech (music signal vs. noise) processing, left implantation showed functional advantages over right implantation that were not yet discernable using clinical, questionnaire-based outcome measures. These findings support the notion that the right hemisphere develops earlier and is better preserved from adverse environmental influences than its left counterpart. This study thus provides, to our knowledge, the first evidence for differential influences of left and right auditory peripheral stimulation on early cortical development of the human brain.

Children’s Neural Sensitivity to Prosodic Features of Natural Speech and Its Significance to Speech Development in Cochlear Implanted Children

“…Considering all the children with CI were right-sided implanted, there is a possibility that the laterality of neural activities was influenced by the implantation laterality. However, there was a study suggesting that cortical processing of speech showed no influence on the implantation side in children ( Wang et al, 2022 ). Thus, we postulated that the laterality of CI was not an essential factor for this result.…”

Reduction of right-hemispheric auditory cortex activity in response to speech in more experienced paediatric cochlear implant users

“…On the other hand, fNIRS studies that used running speech as stimulus yielded conflicting results and did not assess speech-evoked activity longitudinally. Wang et al (2022) found no significant speech-evoked activity in either hemisphere for young pre-lingually deafened CI users directly after implantation and 1.5 months later, while Zhou et al (2023) reported larger bilateral activity compared to a NH control group in experienced pre-lingually deafened children with CIs. Bilateral speech-evoked activity in auditory areas was also observed in experienced pre-lingually deafened CI users of the same age as in the current study (Mushtaq et al, 2020), consistent with the current CI – T2 results.…”

“…The absence of this effect thus raises the question whether fNIRS is at all suitable for reliably detecting auditory cortex activity in paediatric subjects. Furthermore, changes in speech-evoked cortical activity were so far only assessed during the first few months after implantation (Petersen et al, 2013; Sevy et al, 2010; Wang et al, 2022) and it thus remains unclear if left-lateralised activity in pre-lingually deafened paediatric CI users might emerge with more CI experience. Additionally, only two fNIRS studies to date investigated the cortical processing of prosodic features in paediatric CI users (Chen et al, 2022; Wang et al, 2021) and neither of them reported the right-lateralisation of activity in response to prosodic modulations typically observed in NH infants (Homae et al, 2006; Homae et al, 2012; Telkemeyer et al, 2011) and children (Wartenburger et al, 2007).…”

Effects of Age on the Auditory Cortex During Speech Perception in Noise: Evidence From Functional Near-Infrared Spectroscopy

“…Last, we removed hemodynamic signals, unrelated noise components, and unknown global deviations caused by respiratory, cardiac, and vascular movements or other experimental errors. The processed HbO signals ( Wang et al 2022 ) were then fitted to a general linear model which included regressors created by convolving a boxcar function for the five SNR conditions; the duration was equal to the average stimulus length of 20 sec. This part of the study involved an statistical parametric mapping hemodynamic response model.…”