December 21, 2004
Early Learning Has Lasting Effects
Research with owls offers insights into how children learn language
HealthDayNews -- In a finding that offers insights into how young children learn language, researchers have discovered the early learning experiences of owls forever alter their brain circuitry.Young barn owls are very good at identifying the source of a sound -- they have to be to hunt and survive. But can they compensate if their ability to locate sounds is altered?
Stanford University researchers found they can -- by creating new pathways in the brain that allow the animals to locate sounds even when their visual perception is changed.
As the birds became adults, they reverted to their normal brain pathway -- a connection of brain cells called neurons -- to locate sounds. But when their vision was temporarily altered again, they were able to switch to the alternate pathway that had been created when they were young.
"The main issue in this study is how the brain learns from experience," said lead researcher Eric Knudsen, chairman of the neurobiology department at Stanford University's School of Medicine. "We hypothesized that the change was an anatomical change."
The findings appear in the Dec. 19 online issue of Nature Neuroscience.
"The impact of early learning in the owls is very reminiscent of language learning in human infants," said Patricia K. Kuhl, co-director of the Institute for Learning and Brain Sciences at the University of Washington.
"My studies show that early experience with a language commits brain tissue to the acoustic patterns of that language. And this early learning affects future learning," Kuhl said.
In the owl experiments, Knudsen and his colleagues placed glasses over the young owls' eyes, shifting the perception of where sounds were coming from. "We changed the relationship between what the owl hears and where he thinks the sound came from," Knudsen said.
Over several weeks, the owls were able to adjust what they heard to match their optically altered world. "We saw the architecture of neurons systematically altered by this juvenile experience," Knudsen said.
When the glasses were removed, the owls went back to using the normal sensory pathway, he noted.
However, as adults, the owls were able to use the alternate neuron pathway when their eyes were covered again with the glasses. But, adult owls that had their eyes covered with glasses for the first time weren't able to compensate for the visual and auditory mismatch, Knudsen explained.
"These architectural changes in the brain are very persistent and persist into adulthood, and can be re-expressed if it becomes useful," Knudsen said. "Parts of the brain that are learning fundamental things about the world are being altered structurally in ways that are going to influence how they [the owls] process information in adulthood, and therefore have long-term implications for cognitive abilities and social capabilities."
The same is true for children, Kuhl said.
"It's as though you've got real estate in the brain that gets dedicated to one activity, and thereafter reinforces other things involving that activity, while at the same time inhibiting the learning of activities that are incompatible with the initial one," Kuhl said.
"If you learn the sounds of one language, which you do by 12 months of age -- like English, where 'r' and 'l' are used to create distinct words -- and then you try and learn Japanese where these two sounds are not distinct, your brain has a hard time having it both ways," she explained.
"However, in early development, before the real estate in the brain is committed, you actually can have it both ways. "We think two independent circuits get wired, one for each language," Kuhl said.
After puberty, it's much tougher to dedicate circuits to a completely new language, Kuhl said. "We're trying to understand how this works, and we think that early learning drives the process. Even small amounts of early language exposure make a difference."
The National Institute on Deafness and Other Communication Disorders can tell you more about how language develops.