Abstract
Activation of the auditory cortex by visual stimuli has been reported in deaf children. In cochlear implant (CI) patients, a residual, more intense cortical activation in the frontotemporal areas in response to photo stimuli was found to be positively associated with poor auditory performance. Our study aimed to investigate the mechanism by which visual processing in CI users activates the auditory-associated cortex during the period after cochlear implantation as well as its relation to CI outcomes. Twenty prelingually deaf children with CI were recruited. Ten children were good CI performers (GCP) and ten were poor (PCP). Ten age- and sex- matched normal-hearing children were recruited as controls, and visual evoked potentials (VEPs) were recorded. The characteristics of the right frontotemporal N1 component were analyzed. In the prelingually deaf children, higher N1 amplitude was observed compared to normal controls. While the GCP group showed significant decreases in N1 amplitude, and source analysis showed the most significant decrease in brain activity was observed in the primary visual cortex (PVC), with a downward trend in the primary auditory cortex (PAC) activity, but these did not occur in the PCP group. Meanwhile, higher PVC activation (comparing to controls) before CI use (0M) and a significant decrease in source energy after CI use were found to be related to good CI outcomes. In the GCP group, source energy decreased in the visual-auditory cortex with CI use. However, no significant cerebral hemispheric dominance was found. We supposed that intra- or cross-modal reorganization and higher PVC activation in prelingually deaf children may reflect a stronger potential ability of cortical plasticity. Brain activity evolution appears to be related to CI auditory outcomes.
Highlights
Over the past several decades, individuals with severe to profound sensorineural hearing loss mostly benefitted from cochlear implants (CI)
On the basis of the category of auditory performance (CAP) scores (Archbold et al, 1995) and according to the 12M follow-up, they were divided into two group: (1) 10 subjects with CAP scores > 5 were assigned to the CI good CI performer group (GCP) and the remaining 10 with CAP scores ≤ 5 were in the poor CI performer group
Our present study used eventrelated potential (ERP) components and distributed source localization originating from risk-free highdensity EEG recordings to carefully identify and follow cortical activity in CI users
Summary
Over the past several decades, individuals with severe to profound sensorineural hearing loss mostly benefitted from cochlear implants (CI). Many factors are associated with the auditory speech perception in CI recipients, including the age at which the CI was received, cognitive abilities, family environment, etiology, and speech-language therapy (Schramm et al, 2002; Liang et al, 2014; Sharma et al, 2015) Of these factors, age at implantation is the most important factor in terms of CI outcome (Sharma et al, 2015). A large portion of variability in CI outcome remains unexplained by these models (Lazard et al, 2013) Such as in the study by Schramm et al (2002), their results showed CI patients with prelingual deafness achieved significantly better speech understanding using phonetically balanced monosyllabic words, there was a wide performance range among patients(Schramm et al, 2002; Lazard et al, 2013). They suggested that this may be due to the extent of visual cross-modal impact on the auditory cortex
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