This Research Topic is part of the article collection series,
Changes in the Auditory Brain Following Deafness, Cochlear Implantation, and Auditory Training.
The auditory brain receives sound information sent from lower levels of the auditory system and acts as a relay station for auditory perception. In individuals with sensorineural hearing loss, sound deprivation would result in neurological changes that affect neural coding of sound frequency, intensity, and duration. With long-term deafness, the auditory brain displays structural and functional abnormalities.
Deafness-related neural changes can be at least partially reversed by the reintroduction of stimulation through a cochlear implant (CI). The CI transforms acoustic stimuli into electrical signals and delivers these signals to the auditory nerve through the electrodes implanted in the inner ear. While the passive exposure of sound after implantation can result in improvement of hearing capability over time (typically in the first year) until a plateau is reached, active auditory training has been reported to further improve CI outcomes. Understanding the neural substrates of hearing in CI users before and after implantation will result in better ways to identify individuals who can or cannot receive sufficient benefits from CI devices, to identify the neural barriers to CI benefits in poor performers, and to point in the direction of auditory training strategies. Additionally, the neural measures can serve as objective tools to monitor neurological plasticity following cochlear implantation and post-implantation training.
Imaging the brain in both space and time (for example, by using electroencephalography/EEG, electrocorticography/ECoG, magnetoencephalography/MEG, and functional magnetic resonance imaging/fMRI and other imaging modalities) has been used to provide information on the differences between individuals with normal and abnormal auditory processing, as well as the neural changes associated with hearing loss, cochlear implantation, and auditory intervention.
Different modalities of imaging tools have different advantages, disadvantages, and applications. EEG and MEG can be used to record auditory evoked activities from the scalp with an excellent temporal resolution. The ECoG responses are recorded directly from the human cortex. The ECoG is a unique instrument for studying the neural basis of auditory processing and reorganization of neural substrates responsible for this processing in clinical populations. The fMRI can provide information on brain activity by detecting changes associated with blood flow, with a high spatial resolution but low temporal resolution. It is challenging to conduct MEG and fMRI studies in patients with active CIs due to the conflict between the CI and the magnetic field. Consequently, MEG and fMRI may play a key role in the pre-operative evaluation of cochlear implantation.
In this Research Topic, we are interested in highlighting contributions of various brain imaging methodologies to understanding the neural effects of deafness, as well as brain plasticity because of cochlear implantation and post-implantation auditory training. We also welcome research on normal-hearing listeners who experience auditory training, such as musicians, to provide further insight into the effects of auditory training on the brain.