Increased audiovisual integration in cochlear‐implanted deaf patients: independent components analysis of longitudinal positron emission tomography data

Abstract

It has been demonstrated in earlier studies that patients with a cochlear implant have increased abilities for audio-visual integration because the crude information transmitted by the cochlear implant requires the persistent use of the complementary speech information from the visual channel. The brain network for these abilities needs to be clarified. We used an independent components analysis (ICA) of the activation (H2(15)O) positron emission tomography data to explore occipito-temporal brain activity in post-lingually deaf patients with unilaterally implanted cochlear implants at several months post-implantation (T1), shortly after implantation (T0) and in normal hearing controls. In between-group analysis, patients at T1 had greater blood flow in the left middle temporal cortex as compared with T0 and normal hearing controls. In within-group analysis, patients at T0 had a task-related ICA component in the visual cortex, and patients at T1 had one task-related ICA component in the left middle temporal cortex and the other in the visual cortex. The time courses of temporal and visual activities during the positron emission tomography examination at T1 were highly correlated, meaning that synchronized integrative activity occurred. The greater involvement of the visual cortex and its close coupling with the temporal cortex at T1 confirm the importance of audio-visual integration in more experienced cochlear implant subjects at the cortical level.

Parallel linear dynamic models can mimic the McGurk effect in clinical populations

“…These results find support in the neuroimaging literature showing different patterns of visual activation in postlingually deafened adult cochlear implant (CI) users (Strelnikov et al 2015; see Bergeson and Pisoni 2004, for behavioral studies involving CI users). In a PositronEmission-Tomography (PET) study, Strelnikov et al (2015) compared occipital-temporal activation patterns in three groups of listeners in an audiovisual speech perception task: normal-hearing listeners, recently implanted CI users, and CI users that had been implanted several months prior.…”

“…Control results were obtained from simulation 1 (not shown again in Fig. 3 the predictions of the interactive model that predicts the McGurk effect (Bergeson and Pisoni 2004;Dodd et al 2008;Strelnikov et al 2015). Our second round of simulations showed that systematically varying the inhibition parameter value allows the model to predict the rate of the McGurk effect within individual ASD listeners.…”

“…Deviations from the expected McGurk fusion indicate weakened sensory input as in aging or hearing-impaired populations, or insufficiently developed cross-modal speech representations, which have been observed in many ASD or schizophrenia listeners. One important facet of this approach is that changes in audiovisual response profiles can occur well into adulthood (e.g., Sekiyama et al 2013) and even subsequent to CI implantation in adults (Strelnikov et al 2015). As such, assessing listener's responses to McGurk stimuli should continue to be a powerful barometer of multisensory performance.…”

“…In a PositronEmission-Tomography (PET) study, Strelnikov et al (2015) compared occipital-temporal activation patterns in three groups of listeners in an audiovisual speech perception task: normal-hearing listeners, recently implanted CI users, and CI users that had been implanted several months prior. The authors employed independent component analysis to the PET signals; they reported greater left mid-temporal blood flow in the group that had been implanted several months prior compared to the newly implanted and normal-hearing groups.…”

“…This configuration was designed to show how visual speech cues can facilitate degraded auditory input in both children and adults with a history of abnormal auditory development, hearing-impairment, or CI use (see Strelnikov et al 2015). As designed, the model allowed auditory cues consistent with the visually articulated consonant "g" to be reported or "heard"; hence, "g" or "d" should be perceived with similar likelihood.…”