A new understanding of how some visually impaired adults can begin to see offers a fresh perspective on the brain’s capabilities. A collaboration between researchers at the University of California, Irvine School of Biological Sciences and the School of Medicine led to the discovery that the adult brain has the potential to partially recover sight from inherited blindness. Their paper was published in Current Biology.

How Researchers Could Help Recover Sight

The researchers were looking into a treatment for Leber congenital amaurosis, also known as LCA. The term is used to describe a group of inherited retinal diseases that are distinguished by severe visual impairment at birth. The condition, caused by mutations in any of over two dozen genes, causes photoreceptor degeneration or dysfunction in the retina. Synthetic retinoids, which are chemical compounds that target the retina, can restore a significant amount of vision in children with LCA.
The UCI researchers wanted to see if the treatment could help adults with the condition.

Frankly, we were blown away by how much the treatment rescued brain circuits involved in vision,” said Sunil Gandhi, professor of neurobiology and behavior and the corresponding author. Gandhi is a fellow of UCI’s Center for the Neurobiology of Learning and Memory and a member of the Center for Translational Vision Research. “Seeing involves more than intact and functioning retinae. It starts in the eye, which sends signals throughout the brain. It’s in the central circuits of the brain where visual perception actually arises.” Until now, scientists believed that the brain must receive those signals in childhood so that central circuits could wire themselves correctly.

Working with rodent models of LCA, the collaborators were surprised by what they found. “The central visual pathway signaling was significantly restored in adults, especially the circuits that deal with information coming from both eyes,” Gandhi said. “Immediately after the treatment, the signals coming from the opposite-side eye, which is the dominant pathway in the mouse, activated two times more neurons in the brain. What was even more mind-blowing was that the signals coming from the same-side eye pathway activated five-fold more neurons in the brain after the treatment and this impressive effect was long-lasting. The restoration of visual function at the level of the brain was much greater than expected from the improvements we saw at the level of the retinae. The fact that this treatment works so well in the central visual pathway in adulthood supports a new concept, which is that there is latent potential for vision that is just waiting to be triggered.”

The discovery opens up exciting research opportunities. “Whenever you have a discovery that defies your expectations about the brain’s ability to adapt and rewire, it teaches you a broader concept,” Gandhi explained. “This new paradigm could aid in the development of retinoid therapies to more completely rescue the central visual pathway of adults with this condition,” the researchers write.

Gandhi and the project’s first author, Carey Huh, PhD, collaborated with Krzysztof Palczewski, Distinguished Professor of Ophthalmology. Palczewski, the Center for Translational Vision Research’s director, is well-known for his research on retinoids and the visual cycle. Philip Kiser, associate professor of physiology and biophysics and a visual cycle biochemistry expert, assisted in leading the group. Kiser is a member of the Center for Translational Vision Research and has a joint appointment in ophthalmology.

The National Institutes of Health, the Department of Veterans Affairs, and the Research to Prevent Blindness foundation funded the study.

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Source: University of California – Irvine. “Eye-opening discovery about adult brain’s ability to recover vision: The adult brain has the potential to partially recover from inherited blindness.” ScienceDaily. ScienceDaily, 6 October 2022. <www.sciencedaily.com/releases/2022/10/221006121213.htm>.

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