This Week in Research: Lazy Eye and Radiation Brain

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Amblyopia, aka lazy eye, happens when a person’s eyes are mismatched — one is weaker than the other, or they’re misaligned, or they focus differently — and if it’s not corrected very early on, it becomes a problem for life. Basically, very young children have flexible brains that can learn to adapt to corrected vision in a way that adult brains are pretty much incapable of doing. But a team of University of Maryland researchers think they may have found a way to trick the adult brain into rewiring itself.

The researchers found that around five years of age in humans (and five weeks of age in mice), the brain basically becomes less plastic — and therefore less able to rewire the neural circuitry required for seeing and processing visual information. They pinpointed a particular synapse-controlling protein, NARP, as one critical feature.

To simulate amblyopia, the researchers covered one eye in two groups of mice, one with the NARP gene and one without it. The mice with NARP had vision problems as expected; essentially, their brain circuits tried to compensate, and ended up comparatively weaker. But the non-NARP mice developed normal vision.  “It’s remarkable how specific the deficit is,” said UMD neuroscientist Elizabeth Quinlan. Without the NARP protein, “these animals develop normal vision. Their brain circuitry just isn’t plastic. We can completely turn off the critical period for plasticity by knocking out this protein.”

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I like Johns Hopkins neuroscientist Alfredo Quinones-Hinojosa; he has a way with words: “Despite being hit hard by radiation, it turns out that neural stem cells are like special forces, on standby waiting to be activated. Now we might figure out how to unleash the potential of these stem cells to repair human brain damage.”

Quinones-Hinojosa wants to call in the (neural) troops because a recent study of his has found that, contrary to previous assumptions, brain stem cells can regenerate after being hit with a dose of radiation. In the experiment, Quinones-Hinojosa and his team simulated localized radiation in mice for several weeks, then injected them with a substance that induces brain damage. (Poor mice.) But the damage actually managed to reinvigorate the neural stem cells in the irradiated part of the brain, even though they’d been dormant post-radiation. The stem cells rallied themselves and began generating new cells to deal with the brain damage.

“The brain has some innate capabilities to regenerate and we hope there is a way to take advantage of them. If we can let loose this potential in humans, we may be able to help them recover from radiation therapy, strokes, brain trauma, you name it,” Quinones-Hinojosa said.



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