Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. C URRENT O PINION The brain as a flexible task machine: implications for visual rehabilitation using noninvasive vs. invasive approaches Lior Reich a , Shachar Maidenbaum a , and Amir Amedi a,b Purpose of review The exciting view of our brain as highly flexible task-based and not sensory-based raises the chances for visual rehabilitation, long considered unachievable, given adequate training in teaching the brain how to see. Recent advances in rehabilitation approaches, both noninvasive, like sensory substitution devices (SSDs) which present visual information using sound or touch, and invasive, like visual prosthesis, may potentially be used to achieve this goal, each alone, and most preferably together. Recent findings Visual impairments and said solutions are being used as a model for answering fundamental questions ranging from basic cognitive neuroscience, showing that several key visual brain areas are actually highly flexible, modality-independent and, as was recently shown, even visual experience-independent task machines, to technological and behavioral developments, allowing blind persons to ‘see’ using SSDs and other approaches. Summary SSDs can be potentially used as a research tool for assessing the brain’s functional organization; as an aid for the blind in daily visual tasks; to visually train the brain prior to invasive procedures, by taking advantage of the ‘visual’ cortex’s flexibility and task specialization even in the absence of vision; and to augment postsurgery functional vision using a unique SSD–prostheses hybrid. Taken together the reviewed results suggest a brighter future for visual neuro-rehabilitation. Keywords blindness, brain organization, multisensory integration, sensory substitution, vision INTRODUCTION Severe visual impairments, varying in cause and severity, affect over 200 000 000 people worldwide, constituting a major clinical and scientific challenge to develop effective visual rehabilitation tech- niques. One such class of invasive approaches aims at restoring the function of the peripheral visual system, for instance using artificial retinal prosthe- ses (‘bionic eyes’ [1 & ,2 & ,3 && ,4,5]), using gene therapy [6 && ] or by transplantation of photoreceptors [7 & ] (see [8 & ,9 & ] for recent reviews of the various methods). However, these promising solutions are facing huge challenges as they have not yet achieved sufficient technical capabilities, need to be tailored to the impairments’ specific cause, are expensive and invasive and have, at least so far, very low- resolution end-result sight. An alternative and promising direction to follow, which was demon- strated to have a much better functional perform- ance, is the use of sensory substitution devices (SSDs), which offer rehabilitation at the central nervous system level while bypassing the nonfunc- tioning peripheral components. SSDs are noninva- sive human–machine interfaces, which, in the case of the blind, transform visual information into audi- tory or tactile representations using a predetermined transformation algorithm. Although this is not intuitively thought of as ‘real’ vision, and usually a Department of Medical Neurobiology, The Institute for Medical Research Israel-Canada, Faculty of Medicine and b The Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University of Jerusalem, Jerusalem, Israel Correspondence to Amir Amedi, PhD, Department of Medical Neuro- biology, The Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 91220, Israel. Tel: +972 2 675 7259; fax: +972 2 675 8602; e-mail: amir.amedi@ ekmd.huji.ac.il Curr Opin Neurol 2012, 25:000–000 DOI:10.1097/WCO.0b013e32834ed723 1350-7540 ß 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins www.co-neurology.com REVIEW