How birds sing
September 27, 1996
In a new finding with implications to human learning, memory, and speech acquisition, researchers at the University of Chicago Medical Center have correlated the simple notes and more complex passages of a bird's song to activity in different areas of the brain.
The researchers were able to show for the first time that structures higher up in the brain's chain of command directly control the more abstract information, while the component bits are managed by lower brain centers. The research is reported in today's issue of the journal Science.
Daniel Margoliash, PhD, associate professor of organismal biology and anatomy, and Albert Yu, MD, a graduate student in neurobiology, have provided the most detailed look yet at how the brain controls singing in the zebra finch, which Margoliash calls the "white rat" of songbirds. Neurobiologists have used them extensively to study brain function.
"It doesn't have the most beautiful song," admits Margoliash. "It sounds like a squeaky door. But it's a wonderful system for studying learning and memory, which are central questions in neurobiology," he said. "It's interesting to human biology, because song learning in birds has compelling similarities to speech acquisition."
The research shows that the score for the bird's song takes shape as it gets relayed down a hierarchy of brain structures. The main themes--what the scientists call "syllables" --are composed by the higher structures, but the individual notes get filled in by the lower brain regions. This sort of hierarchical organization of the brain's motor functions had long been supposed by neuroscientists but never demonstrated.
Margoliash and Dr. Yu measured the electric impulses that form the musical instructions by outfitting 13 male finches with special headgear with brain electrodes. The four electrodes were poised above a region called the HVc, known to be part of the bird's song production system, or another region called the RA, a subordinate region that receives input from the HVc and activates the muscles of the syrinx--the bird's voicebox. They recorded electrical activity just outside individual brain cells of interest, and compared the signal with sounds the birds made.
The impulses in the RA coincided with individual notes, each lasting just a few hundredths of a second, while the signature firing pattern from the HVc corresponded to a syllable, or group of notes, lasting in the range of a quarter of a second.
Margoliash said the goal now is to see how the brain learns the song, by comparing adult birds to immature ones or those that are raised in isolation or have diminished hearing.
"What we can hope to find eventually is: How does learning influence the activity patterns of individual neurons? We're learning how the circuits are put together, and we should gain insight into what elements of the circuit are modified during learning."
The research was funded by the Whitehall Foundation, a private philanthropy that funds biomedical research with an emphasis on neurobehavioral studies.
In a finding with implications to human speech acquisition, University of Chicago researchers have shown how a bird's brain controls singing and demonstrated for the first time that structures higher up in the brain directly control the more abstract information, while the component bits are managed by lower brain centers.
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