Science News - August 11, 2012

Roads to resculpting

a variety of strategies have been shown to reverse the eye condition known as amblyopia in adult rats. scientists hope some of these same approaches could work in human adults, reinstating a youthful, flexible state that allows for healing.

Dark exposure Paradoxically, animals kept in complete darkness are able to regain some sight during adulthood, presumably through a shift of nerve cell behavior.

Net breakdown using a compound called chondroitinase abc to dissolve components of perineuronal nets, which hold nerve cells in place, improves visual acuity.

Calorie restriction although it’s not clear how it works, a short-term bout of severe calorie-cutting seems to reset the brain’s clock and allow recovery from amblyopia.

Drugs an ssri used to treat depression, fluoxetine (brand name Prozac) can reactivate adult brain plasticity in rodents, leading to a full recovery of vision.

Environment
enrichment
living in a place with
ample time for exercise,
toys and friends boosts
the brain’s malleability
in rats.

these brain-training regimes have yet to be validated).

“We are continuously being exposed to the environment, and those things that impinge upon us are continuously shaping our brains,” Davidson says. So the question isn’t so much whether something can change the brain, but rather, how people can take charge of the process for a desired outcome.

Studies by Levi and his collaborators have found that a certain kind of vision practice can actually help adults see better. Hours of difficult vision training, in which people had to discern hazy lines, for instance, improved vision in people with amblyopia, normal vision and even normal age-related vision decline. People could see sharper images, detect contrasts better and even read small letters faster.

rat image: basel101658/shutterstock; icons: t. dubÉ

Older people’s eyes still sent blurry information to their brain, but the brains were better equipped to handle it, Levi and colleagues wrote in Scientific Reports . Levi believes that the improvement comes from a training-enhanced ability to pay attention to relevant information and ignore the blurred distractions.

There may be a more fun way. Data from Bavelier support a counterintuitive idea: Mindless video games actually make the brain sharper. Action-packed video games like Call of Duty 2 seem to enhance people’s perception, and not just in ways required to get a high score. “You get benefits that ripple,” Bavelier says.

After logging hours at the games, people were better at nimbly switching between two demanding jobs and quickly determining whether a number is even or odd. The results, reported in May in Computers in Human Behavior, suggest that this kind of brain training reopens a window. “What really changes is the ability to locate resources and ignore distractions,” Bavelier says.

Flexibility too far

Efforts toward restoring plasticity hold
great promise, but only when targeted
to hit particular brain systems. If not,
the potential benefits come with some
strong caveats. “I’m very scared of taking
off the brakes,” Hensch says. “They’re
there for a reason.”
Myelin insulation on nerve cells, for
instance, is damaged in patients with
multiple sclerosis. That damage affects
the conduction of nerve impulses, leading
to the hallmark symptoms of the disease.

In Hensch’s lab, the mice genetically
engineered to lack lynx1 protein show
dementia-like damage in their brains
earlier than their normal counterparts.
“After nine months, you see holes in cor-
tex,” Hensch says. Parts of the brain that
are damaged earliest are the most mal-
leable throughout life. “Maybe the price
we pay for plasticity is the susceptibility
to neurodegeneration.”
Brakes may also help the brain know
what not to learn. Extremely proficient
musicians have reported a rare condi-
tion in which neural pathways become
so shaped by playing music that the per-
formers’ brains fuse the control regions
for separate fingers, and the ability to
cleanly pluck a single string is lost.