Exploring the McGurk Effect in Cochlear-Implant Users: A Systematic Review

Speech perception is a neurocognitive process that involves both auditory and visual modalities to interpret the meaning of spoken utterances. The cohesive integration of visual and auditory information (AV integration) improves speech perception. AV integration can also occur even when incongruent auditory and visual information is presented, known as the McGurk effect. The McGurk phenomenon signifies the importance of visual articulatory cues (such as place of articulation) and auditory information for speech perception. The McGurk effect can be decreased or absent in the deaf population even after using amplification devices or cochlear implants (CI) compared to the normal-hearing population. However, cochlear-implanted individuals could integrate auditory and visual information. So, the McGurk paradigm can provide substantial evidence to understand the speech perception mechanism in hard-of-hearing individuals fitted with a CI. So, the present systematic review was carried out using the McGurk paradigm to understand the speech perception mechanism in CI-fitted individuals. A total of six studies were included in the present review as per the inclusion criteria. The current review included the studies with behavioral McGurk experiments only, excluding the studies that used electrophysiological, radiological, or other methods to explore the McGurk effect in the CI. From the present systematic review, it can be delineated that CI users also demonstrate the McGurk effect when they are fitted with a CI at an early age.