By LEE BOWMAN
Scripps Howard News Service
January 20, 2006
"What our experiment demonstrates is a fundamental principle of how the brain pays attention," said Eric Knudsen, a professor of neurobiology at the Stanford University School of Medicine and lead author of the study published Thursday in the journal Nature.
The study showed that the brain circuits that process auditory information are influenced powerfully by circuits that control where the animal is looking. The researchers also found that a brain mechanism used to prioritize information - previously documented only in primates - is also found in birds.
"The ability to hear and the direction of gaze aren't necessarily linked," said Daniel Winkowski, the study's first author and a postdoctoral researcher at Stanford.
Animals of all sorts hear sounds around them quite well without actually looking in the directions they're coming from. But as any parent who's ever lectured a child knows, the attention of the eyes helps bring focus to what's being said.
"It's exciting to find that the circuits in the brain that control gaze direction affect how the brain processes auditory information," Winkowski added.
The two researchers used electrodes to stimulate the area of the brain responsible for controlling the gaze direction in barn owls, and then studied how that affected the neural responses in brain regions that process auditory information.
When the circuit controlling an owl's gaze was activated, the researchers found that the bird's auditory system responded more strongly and more selectively to sounds that came from the same area as that encoded by the stimulated site. At the same time, the auditory system's response to sounds coming from any other location was suppressed.
This selective filtering of certain information by the brain is critical for normal function in animals. But most of the research done on the mechanism of attention up until now has involved working with monkeys and how they tune out visual information other than what their eyes focus upon.
The new research suggests that the brain uses a common strategy to focus attention that spans different types of animals and different parts of the brain.
"This paper opens the floodgates for studying a wide range of species," Knudsen said. "The fundamental mechanisms are probably going to be the same in all vertebrates, as even frogs and fish have gaze control."
"The promise here is that because we are doing this in owls (whose brain circuits are amenable to manipulation), we can get at the mechanism of how this works," down to the level of which neurotransmitters and receptors are used to signal attention, Winkowski said.
"Once we learn the circuitry for attention, we plan to use that to drive learning in an efficient way," Knudsen said.
Eventually, the researchers want to adjust circuits of owls' brains in ways that will lead to improved learning function.
The researchers also hope that greater understanding of the mechanisms of attention will point to new approaches in treating human disorders of attention, learning and schizophrenia.
"If you understand mechanistically how something works, then you will know how best to fix it," Knudsen said.
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