Cortical reorganization in postlingually deaf cochlear implant users: Intra-modal and cross-modal considerations

Abstract

With the advances of cochlear implant (CI) technology, many deaf individuals can partially regain their hearing ability. However, there is a large variation in the level of recovery. Cortical changes induced by hearing deprivation and restoration with CIs have been thought to contribute to this variation. The current review aims to identify these cortical changes in postlingually deaf CI users and discusses their maladaptive or adaptive relationship to the CI outcome. Overall, intra-modal and cross-modal reorganization patterns have been identified in postlingually deaf CI users in visual and in auditory cortex. Even though cross-modal activation in auditory cortex is considered as maladaptive for speech recovery in CI users, a similar activation relates positively to lip reading skills. Furthermore, cross-modal activation of the visual cortex seems to be adaptive for speech recognition. Currently available evidence points to an involvement of further brain areas and suggests that a focus on the reversal of visual take-over of the auditory cortex may be too limited. Future investigations should consider expanded cortical as well as multi-sensory processing and capture different hierarchical processing steps. Furthermore, prospective longitudinal designs are needed to track the dynamics of cortical plasticity that takes place before and after implantation.

McGurk stimuli for the investigation of multisensory integration in cochlear implant users: The Oldenburg Audio Visual Speech Stimuli (OLAVS)

“…Furthermore, a recent study showed cross-modal reorganization of the visual cortex in CI users (Chen, Sandmann, Thorne, Bleichner, & Debener, 2015). The relationship between the reorganization of visual and auditory cortices in response to auditory sensory deprivation may be linked to speech recognition performance (see Stropahl, Chen, & Debener (2016) for a review). It is therefore important to investigate the integration of information from both modalities to further our understanding of neural changes due to auditory deprivation (and subsequent auditory restoration).…”

Acoustic Change Responses to Amplitude Modulation in Cochlear Implant Users: Relationships to Speech Perception

“…Similarly, significant N1 latency differences between good and poor CI performers were revealed in the present study. Brain plasticity associated with hearing loss has been suggested to underlie the cortical activation pattern with hearing loss and/or with CI use (Pantev et al, 2006;Stropahl et al, 2017). However, the degree of brain plasticity can be different among CI users depending on demographic factors and environmental influences, including rehabilitation.…”

Multisensory Integration in Cochlear Implant Recipients

“…Neuroimaging studies of crossmodal plasticity following cochlear implantation have utilized fNIRS (Saliba et al 2016), PET (Strelnikov et al 2015a), and EEG (Sharma et al 2015) to investigate the neural correlates of these visual perceptual enhancements. Here, we will briefly discuss several representative studies from this substantial body of work (for a thorough review of the topic of crossmodal plasticity in CI users, see Anderson et al 2016; Stropahl et al 2016). …”