Expansion of the Functional Border of the Audiovisual Cortex Following Partial Hearing Loss in Adulthood

Following damage to a major sense (e.g., hearing loss), crossmodal plasticity occurs whereby there is an increased responsiveness in the deprived cortex to the remaining, intact senses. Using a rat model and single‐unit electrophysiological recordings, our recent studies on hearing‐impaired animals have revealed that crossmodal plasticity is not restricted to the core auditory cortex; higher‐order auditory regions as well as visual and audiovisual cortices show differential effects following noise‐induced hearing loss. To our surprise, the cortical area showing the greatest relative degree of multisensory convergence transitioned away from the normal audiovisual area toward a neighboring, predominantly auditory area. Thus, our collective results suggest that crossmodal plasticity induced by adult‐onset hearing impairment manifests in higher‐order cortical areas as an expansion in the functional border of the audiovisual cortex. Our ongoing studies seek to determine the implications of this crossmodal plasticity on the rats' ability to perceive the precise timing of audiovisual stimuli using novel behavioral tasks that are consistent with studies of perceptual judgement in humans. Support or Funding Information Support provided by an NSERC Discovery Grant