A pilot investigation of audiovisual processing and multisensory integration in patients with inherited retinal dystrophies

Mark H Myers,Gavin M Bidelman,Alessandro Iannaccone

doi:10.1186/s12886-017-0640-y

Mark H Myers, Gavin M Bidelman + Show 1 more

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https://doi.org/10.1186/s12886-017-0640-y

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Abstract

BackgroundIn this study, we examined audiovisual (AV) processing in normal and visually impaired individuals who exhibit partial loss of vision due to inherited retinal dystrophies (IRDs).MethodsTwo groups were analyzed for this pilot study: Group 1 was composed of IRD participants: two with autosomal dominant retinitis pigmentosa (RP), two with autosomal recessive cone-rod dystrophy (CORD), and two with the related complex disorder, Bardet-Biedl syndrome (BBS); Group 2 was composed of 15 non-IRD participants (controls). Audiovisual looming and receding stimuli (conveying perceptual motion) were used to assess the cortical processing and integration of unimodal (A or V) and multimodal (AV) sensory cues. Electroencephalography (EEG) was used to simultaneously resolve the temporal and spatial characteristics of AV processing and assess differences in neural responses between groups. Measurement of AV integration was accomplished via quantification of the EEG’s spectral power and event-related brain potentials (ERPs).ResultsResults show that IRD individuals exhibit reduced AV integration for concurrent audio and visual (AV) stimuli but increased brain activity during the unimodal A (but not V) presentation. This was corroborated in behavioral responses, where IRD patients showed slower and less accurate judgments of AV and V stimuli but more accurate responses in the A-alone condition.ConclusionsCollectively, our findings imply a neural compensation from auditory sensory brain areas due to visual deprivation.

Highlights

In this study, we examined audiovisual (AV) processing in normal and visually impaired individuals who exhibit partial loss of vision due to inherited retinal dystrophies (IRDs)
We focused on AV integration in cases of inherited retinal dystrophies (IRDs), in order to further understand the neural mechanisms of multi-modal processing
We show that IRD individuals have reduced AV processing and/or integration of multisensory cues, consistent with their impaired unimodal visual input, and those IRD patients demonstrate increased responsiveness to auditory stimuli, consistent with the notion that visual deficits are partially compensated by recruitment and perhaps expansion of auditory function [17]

Summary

Introduction

We examined audiovisual (AV) processing in normal and visually impaired individuals who exhibit partial loss of vision due to inherited retinal dystrophies (IRDs). Investigation of multi-modal stimulation has found that when auditory (A) and visual (V) stimuli are presented simultaneously, congruent information can change an individual’s object perception. If the dual stimulation is staggered in such a way as to convey a delayed time to contact of approaching stimuli, visual stimulation usually provides a more salient response. AV stimuli elicit a complex cortical network featuring activation in the primary auditory and visual cortices, as well as several multisensory areas (superior temporal sulcus, intraparietal sulcus, insula, and pre-central cortex). Several other studies have found that unimodal sensory input can influence neural responses found in other distal areas normally responsible for processing different sensory modalities [30]. Lip-reading from visual-only videos of mouth movement is associated with responses in auditory cortices (i.e., Heschl’s gyrus and Planum temporale) even if no auditory

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