Visual Activity Regenerates Neural Connections Between Eye, Brain

Regenerating mouse retinal ganglion cell axons (magenta and green) extending from site of optic nerve injury (l)

Photo: Andrew D. Huberman

An NIH-funded study in mice shows for the first time that high-contrast visual stimulation can help damaged retinal neurons regrow optic nerve fibers, otherwise known as retinal ganglion cell axons. In combination with chemically induced neural stimulation, axons grew further than in strategies tried previously. Treated mice partially regained visual function. The study also demonstrates that adult regenerated central nervous system (CNS) axons are capable of navigating to correct targets in the brain. The research was funded through the National Eye Institute. 

“Reconnecting neurons in the visual system is one of the biggest challenges to developing regenerative therapies for blinding eye diseases like glaucoma,” said NEI director Dr. Paul Sieving. “This research shows that mammals have a greater capacity for central nervous system regeneration than previously known.”

The researchers induced optic nerve damage in mice behind one eyeball. The mice were then placed in a chamber several hours a day for 3 weeks where they viewed high-contrast images—essentially changing patterns of black lines. The mice had modest but significant axonal regrowth compared to control mice that did not receive the high-contrast visual stimulation.

“We saw the most remarkable growth when we closed the good eye, forcing the mice to look through the injured eye,” said Dr. Andrew Huberman of Stanford University School of Medicine’s department of neurobiology, lead author of the report published online July 11 in Nature Neuroscience. In 3 weeks, the axons grew as much as 12 millimeters, a rate about 500 times faster than untreated CNS axons.

The regenerating axons also navigated to the correct brain regions, a finding that Huberman said sheds light on a pivotal question in regenerative medicine: “If a nerve cell can regenerate, does it wander or does it recapitulate its developmental program and find its way back to the correct brain areas?”