A Quantitative Electroencephalography Study on Cochlear Implant-Induced Cortical Changes in Single-Sided Deafness...

Area of Science:

• Neuroscience
• Audiology
• Medical Imaging

Background:

• Tinnitus suppression after cochlear implantation (CI) in single-sided deafness (SSD) lacks a clear mechanistic explanation.
• Understanding the neurophysiological changes underlying tinnitus relief is crucial for optimizing CI outcomes.

Purpose of the Study:

• To investigate cortical activity and functional connectivity changes associated with tinnitus suppression following CI in SSD patients.
• To differentiate between peripheral reafferentation and cortical plasticity as mechanisms for tinnitus improvement.

Main Methods:

• Quantitative electroencephalography (qEEG) was used to record brain activity in SSD patients at three time points: pre-CI, 6 months post-CI (CI-on), and immediately after device deactivation (CI-off).
• Source-localized cortical activity and functional connectivity analyses were performed on the qEEG data across different frequency bands (delta, beta2, gamma).

Main Results:

• CI-on significantly reduced activity in the right auditory and orbitofrontal cortices (OFC) and decreased auditory-posterior cingulate cortex connectivity compared to baseline.
• CI-on also showed reduced activity in auditory and frontal regions across delta and gamma bands compared to CI-off.
• No significant qEEG differences were observed between CI-off and baseline conditions, suggesting a lack of persistent cortical changes.

Conclusions:

• Cochlear implantation induces dynamic changes in cortical activity and functional connectivity, contributing to tinnitus suppression in SSD.
• These observed changes are primarily attributed to peripheral reafferentation from the CI device, rather than adaptive cortical plasticity.
• The findings suggest that the tinnitus relief is a direct consequence of auditory input modulation rather than a long-term alteration of brain networks.