The WHO estimates that there are over 1.5 million blind children in the world, of whom nearly 90% live in the developing nations (WHO Factsheet 282, 2011; Gogate and Gilbert, 2007). Many are congenitally blind. The visual handicap, coupled with extreme poverty greatly compromises the children?s quality of life. Over 20% of such children have treatable conditions such as congenital cataracts, but most of them never receive medical care because of financial hardship or lack of medical access. The pressing humanitarian need to bring sight- restoring surgeries to these children also opens up an unprecedented scientific opportunity to study a fundamental open question: How does the brain learn to extract meaning from sensory information? Project Prakash is an NIH supported effort that is designed to pursue this dual mission of service and science. The initiative has provided ophthalmic screening to over 40,000 children and sight restoring surgeries to over 450 blind children. Several of them have gone on to participate in scientific studies designed to probe the development of visual proficiencies and cortical changes after sight onset. The findings thus far suggest that consistent with the notion of early sensitive periods for visual development, some key aspects of vision, such as acuity, spatial contrast sensitivity and precise oculomotor stability are compromised by extended deprivation. The compromises appear to be permanent since the measures do not change significantly from soon after the surgery to even a year later. More encouraging results have emerged in studies of ?higher-order? visual functions. Evidence thus far points to partial skill acquisition on tasks such as simple shape matching, spatial imagery and object recognition. This pattern of proficiencies and limitations helps characterize the limits of neural plasticity late in childhood. In clarifying the prospects of visual function acquisition after many years of early blindness, these results hold significance for basic neuroscience as well as the practice of pediatric ophthalmology and the implementation of late stage blindness treatment programs. In the next project period, we propose to build upon the evidence of recovery by more deeply exploring the mechanisms underlying such recovery. Specifically, we shall investigate whether temporal relationships between sensory elements (within and across modalities) play a role in enabling the Prakash children to learn to bind disparate sensory elements into subassemblies, a proxy for parsing sensory arrays into objects. Additionally, we shall examine the development of object recognition in the specific context of faces. For both of these lines of investigation, we shall use behavioral as well as neuroimaging techniques to enable an assessment of the kinds of cortical changes that accompany changes in perceptual proficiencies.
The humanitarian need to provide sight restoring treatments to congenitally, but curably, blind children embodies an unusual scientific opportunity: a window into the process of visual development after late sight onset. From the basic science perspective, this knowledge will provide insights regarding cortical plasticity and the mechanisms of visual learning. From the applied perspective, the results would help formulate prognoses for current and future treatments for blindness, and identify targets for rehabilitation. Project Prakash is an effort that merges these twin humanitarian and scientific objectives.
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|Gandhi, Tapan; Kalia, Amy; Ganesh, Suma et al. (2015) Immediate susceptibility to visual illusions after sight onset. Curr Biol 25:R358-9|
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|Sinha, Pawan; Chatterjee, Garga; Gandhi, Tapan et al. (2013) Restoring vision through ""Project Prakash"": the opportunities for merging science and service. PLoS Biol 11:e1001741|
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