Changes in visually and auditory attended audiovisual speech processing in cochlear implant users: A longitudinal ERP...

Area of Science:

• Neuroscience
• Audiology
• Speech Processing

Background:

• Limited auditory input can be compensated by other senses.
• Cochlear implant (CI) use alters visual skills and cortical processing of unisensory stimuli.
• The impact of auditory deprivation and CI use on cortical audiovisual speech processing remains unclear.

Purpose of the Study:

• To investigate how auditory deprivation and CI use affect cortical audiovisual speech processing.
• To examine alterations in event-related potentials (ERPs) in CI users before and after implantation.
• To compare audiovisual speech processing in CI users and normal-hearing (NH) listeners under different attention conditions.

Main Methods:

• A prospective longitudinal electroencephalography (EEG) study.
• Compared postlingually deafened CI users (before implantation, 5 weeks, and 6 months post-implantation) with matched NH listeners.
• Participants performed an audiovisual word identification task, attending to either visual (lip movement) or auditory speech signals.

Main Results:

• CI candidates and users showed enhanced lipreading and altered auditory cortex responses (decreased theta power, smaller N1 amplitude) compared to NH listeners.
• After implantation, auditory cortex response increased with stronger intra-modal connectivity.
• Both groups showed attention effects on audiovisual processing, but NH listeners exhibited distinct cognitive resource allocation.

Conclusions:

• Auditory deprivation significantly impacts audiovisual speech processing in the auditory cortex, with partial reversal after CI implantation.
• CI users display distinct audiovisual speech processing compared to NH listeners, even with experience.
• Attention strongly influences audiovisual processing in both groups, but cognitive resource allocation differs between CI users and NH listeners.