The researchers hoped to investigate whether the owls' brains would adaptrewiring the neural circuitry over timeto align sounds with their new visual field.
Many Spectacles, Small Steps
Linkenhoker measured the responses of the bespectacled owls' neurons in a region of the birds' brain called the optic tectum, where visual and auditory maps merge. From this data she could determine whether the animals had adapted enough to map a sound to the correct location in their altered visual field.
Within two months of wearing the 23-degree prisms, young owls had fully adapted.
But even after four months of wearing the spectacles, the adults had only adapted about 10 percent as much as the juveniles.
Then Linkenhoker tried another approach. Instead of a one-step, 23-degree shift, Linkenhoker made a series of spectacles that incrementally shifted vision from 6 to 11 to 17 degrees.
With these gradual shifts the adults ramped up their learning curve and achieved slightly more than 50 percent of the juveniles' adjustments.
One overachieving adult owl even made the jump from 17 to 23 degree lensesfully adapting to the shifted visual field, just like the youngsters.
Adaptable vs. Reliable
"Knudsen has shown that adult owls are incapable of large reorganization of neural circuitry in their brains in response to a large change," says Michael Stryker, a neuroscientist at the University of California, San Francisco. "But the study shows that the brain can be coaxed into great plasticity in adulthood with a specially designed training regimen."
The life-stage change makes sense to Linkenhoker. "In the adult, the brain gives up plasticity to gain more reliability," she says. "Whereas for juveniles it is important to adapt quickly, responding to the changing world around them."
In humans, a stroke or an accident can cause the loss of certain skills like speech. But, with the right incremental training, victims may be able to relearn more than ever thought possible, researchers said.
"There's something about successfully performing a task that allows us to build up skillswe reinforce what we know and then expand from this point," Knudsen says.
The lesson from the bespectacled barn owls is that even oldor impairedcreatures can learn new tricks if they proceed by small degrees.
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