NEURO PUBLISHERS ISSN 2377-1607 Open Journal Vision in the Hearing-Impaired: Enhanced or Deprived? Jaikishan Jayakumar, PhD Senior Project Advisor, Center for Computational Brain Research, Indian Institute of Technology, Madras Guindy, Chennai 600036, India * Corresponding author Jaikishan Jayakumar, PhD Senior Project Advisor, Center for Computational Brain Research, Indian Institute of Technology, Madras Guindy, Chennai 600036, India; Tel. +91 44 2257 8921; E-mail: jaikishan.jayakumar@gmail.com Article information Received: March 4 th , 2019; Revised: March 18 th , 2019; Accepted: March 19 th , 2019; Published: March 25 th , 2019 Cite this article Jayakumar J. Vision in the hearing-impaired: Enhanced or deprived? Neuro Open J. 2019; 6(1): 6-9. doi: 10.17140/NOJ-6-130 Mini Review Mini Review | Volume 6 | Issue 1| 6 Copyright 2019 by Jayakumar J. This is an open-access article distributed under Creative Commons Attribution 4.0 International License (CC BY 4.0), which allows to copy, redistribute, remix, transform, and reproduce in any medium or format, even commercially, provided the original work is properly cited. cc INTRODUCTION W e perceive our environment using a wide variety of senses including vision and audition and rely upon them individually or in combination to make sense of our world. Conventional neuroscience dictates that the neuroplastic processes within the brain allow for the effcient use of its available resources. This results in the phenomenon that is not necessarily benefcial, for example the expansion of somatosensory maps following limb amputation results in spurious perceptual events known as “phantom limb pain” 1 or untreated amblyopia results in the profound loss of visual acuity. 2 How this process works during the complete loss of sensory information from one modality is still a topic of debate. One theory suggests that developmentally the loss of one sense, say hearing, will adversely affect other senses as well, this is known as the perceptual defcit hypothesis. On the other hand, there is mounting evidence that when one sensory system affected, there is the reallocation of resources to another system resulting in an enhancement of other sensory systems. This is termed as the perceptual compensatory hypothesis and is believed to be the direct result of the cross-modal plasticity properties of the brain. In this mini-review, we aim to explore both these hypotheses. The Perceptual Defcit Hypothesis The frst hypothesis states that a signifcant defcit in one sensory modality affects the development and organization of the other sensory systems. This is termed as the perceptual defcit hypothesis. In the case of hearing-impaired, the perceptual defcit hypothesis predicts hearing-impaired individuals will exhibit poorer visual and tactile perceptual performance. 3 The secondary assumption is that the lack of one sensory input adversely affects the complex tasks such as language which needs signifcant interaction between the different senses. 4 The hypothesis mainly came about because of the increased prevalence of vision-related abnormalities in the congenitally hearing-impaired that has been reported in the literature. 5,6 The seminal studies by Pollard and Neumaier 5 and by Mohindra 6 where visual problems were found to be much more in hearing-impaired school going children as compared to normal school going children. There is some evidence supporting this hypothesis as the hearing-impaired perform signifcantly worse ABSTRACT By defnition, the hearing-impaired lack one functioning sensory channel that transmits information to the brain. What effect does this have on the perceptual systems of the brain is the subject of the review. There are currently two hypotheses on this matter: The perceptual defcit hypothesis that states that lack of a functioning sensory input affects the development and matu- ration of other sensory channels and results in the impaired functioning of our senses. The second is the perceptual compensa- tion hypothesis which states that when one sensory system is affected, the processing resources within the brain are reallocated to the other sensory system resulting in an enhancement of the other systems. This review is about both these hypotheses and attempts to answer the question if the hearing-impaired can really “see “better. We highlight the important fndings from both these hypotheses and provide growing evidence for the perceptual compensation hypothesis. Keywords Hearing-impaired; Vision; Perceptual defcit; Perceptual compensation; Audition.