Cross-Modal and Intra-Modal Characteristics of Visual Function and Speech Perception Performance in Postlingually Deafened, Cochlear Implant Users

Abstract

Evidence of visual-auditory cross-modal plasticity in deaf individuals has been widely reported. Superior visual abilities of deaf individuals have been shown to result in enhanced reactivity to visual events and/or enhanced peripheral spatial attention. The goal of this study was to investigate the association between visual-auditory cross-modal plasticity and speech perception in post-lingually deafened, adult cochlear implant (CI) users. Post-lingually deafened adults with CIs (N = 14) and a group of normal hearing, adult controls (N = 12) participated in this study. The CI participants were divided into a good performer group (good CI, N = 7) and a poor performer group (poor CI, N = 7) based on word recognition scores. Visual evoked potentials (VEP) were recorded from the temporal and occipital cortex to assess reactivity. Visual field (VF) testing was used to assess spatial attention and Goldmann perimetry measures were analyzed to identify differences across groups in the VF. The association of the amplitude of the P1 VEP response over the right temporal or occipital cortex among three groups (control, good CI, poor CI) was analyzed. In addition, the association between VF by different stimuli and word perception score was evaluated. The P1 VEP amplitude recorded from the right temporal cortex was larger in the group of poorly performing CI users than the group of good performers. The P1 amplitude recorded from electrodes near the occipital cortex was smaller for the poor performing group. P1 VEP amplitude in right temporal lobe was negatively correlated with speech perception outcomes for the CI participants (r = -0.736, P = 0.003). However, P1 VEP amplitude measures recorded from near the occipital cortex had a positive correlation with speech perception outcome in the CI participants (r = 0.775, P = 0.001). In VF analysis, CI users showed narrowed central VF (VF to low intensity stimuli). However, their far peripheral VF (VF to high intensity stimuli) was not different from the controls. In addition, the extent of their central VF was positively correlated with speech perception outcome (r = 0.669, P = 0.009). Persistent visual activation in right temporal cortex even after CI causes negative effect on outcome in post-lingual deaf adults. We interpret these results to suggest that insufficient intra-modal (visual) compensation by the occipital cortex may cause negative effects on outcome. Based on our results, it appears that a narrowed central VF could help identify CI users with poor outcomes with their device.

Somatosensory Cross-Modal Reorganization in Adults With Age-Related, Early-Stage Hearing Loss

“…However, the correlational analysis presented in the current results suggest that greater degrees of cross-modal reorganization are associated with poorer speech perception in noise scores. Interestingly, consistent with the present study, there is some evidence to support the notion that the right temporal cortices are more susceptible to functional reorganization, although the reason for this effect remains to be determined (Finney et al, 2001 ; Sandmann et al, 2012 ; Campbell and Sharma, 2013 , 2014 , 2016 ; Cardin et al, 2013 ; Lin et al, 2014 ; Kim et al, 2016 ; Peelle and Wingfield, 2016 ; Sharma et al, 2016 ; Shiell et al, 2016 ).…”

Auditory cross-modal reorganization in cochlear implant users indicates audio-visual integration

“…Cross-modal reorganization is typically interpreted as a deprivation-induced residual of cortical changes that impedes on speech recovery. Some studies found a maladaptive relationship between processing differences and speech perception in CI users, more specifically, CI users with a higher amount of cross-modal reorganization show a poorer performance in speech perception ( Buckley and Tobey, 2011 , Campbell and Sharma, 2014 , Doucet et al, 2006 , Kim et al, 2016 , Sandmann et al, 2012 ). One has to keep in mind that, in contrast to source estimation as in the current study, some of these correlations are based on scalp EEG analyses, which cannot easily disentangle contributions from different cortical generators (cf.…”

Auditory and Visual Electrophysiology of Deaf Children with Cochlear Implants: Implications for Cross-modal Plasticity

“…To date studies of cross-modal interactions in deaf individuals with CIs have typically reported broad correlations between VEPs and behavioral measures of speech understanding (e.g., Doucet et al, 2006 ; Buckley and Tobey, 2011 ; Sandmann et al, 2012 ; Kim et al, 2016 ). In the present study, we have the ability to examine more directly the relationship between auditory and visual activity.…”

“…Recent work has reported evidence of CMP in pre- and post-lingually deaf adults with CIs which has been suggested to be maladaptive. In studies that have reported maladaptive CMP, the research often makes use of a neural marker of visual processing (e.g., P1 or N1 evoked potentials), and relates this signal to a behavioral processing deficit such as identification of speech in noise ( Doucet et al, 2006 ; Buckley and Tobey, 2011 ; Sandmann et al, 2012 ; Campbell and Sharma, 2016 ; Kim et al, 2016 ). The inference is then made that the altered visual response is causally related to the auditory speech processing and, by association, that auditory cortical regions are vulnerable to reorganization ( Sharma et al, 2015 ).…”