The new brain circuit illuminates the active whisker movement in mice

(newweb.tv) - The new brain circuit has elucidated the development of movements in mouse antennae.

All parents know the important stages of babies: flip, crawl, practice standing and take the first steps without support. Achieving each step probably requires the formation of new connections between subsets of billions of neurons in the infant's brain.

But how, when and where these connections are formed remains a mystery.

Now Duke Medical researchers have begun to find answers. In a study reported on January 23, 2013, in the Neuron scientific journal, the team described the entire network of brain cells connected to muscle-controlled motor neurons. beard in newborn mice.

A better understanding of motor nerve control circuits can help to show how human brains develop, potentially leading to new ways to restore mobility in those people who are paralyzed due to brain damage, or the prospect of developing prosthetic limbs can work better for replacing limbs.

"Beards for mice are like fingers for humans, in both cases are moving to capture the touch ' , research head Fan Wang, Ph.D., assistant professor of cell biology and is member of Duke Research Institute on Brain Science said.

"Learn about how the mouse brain controls their bearded movements can help us understand how the nerves control human finger activity."

Mice are usually active at night, so they rely heavily on their antennae to detect and distinguish reactions to objects in the dark. The behavior of continuous whiskers in mice only began to appear when they were about two weeks old, when the young mice began to explore the world outside the nest.

To learn how to control the beard's motor movement, Wang and his colleague JunTakatoh used a new technique to take advantage of the rabies virus's ability to spread through connected neurons. A form of viral deactivation used to inject mice was created with the ability to express a fluorescent protein. Researchers can track its path through a network of brain cells that connect directly to motor neurons that control whisker movements.

"The accuracy of this mapping method allows us to ask an important question, which is part of a circuit that controls unconnected whiskers in newborn mice and has the same "This lack of connection is added later to allow vibrating whiskers ," Wang said.

By capturing a series of images in fluorescent labeled mouse brains during the first two weeks after birth, the team recorded the growth circuits before and after the mouse began to vibrate. Scientists realize that a lot of cells in the brain are connected to motor neurons that control antennae activity. But how can integrate the activity of these cells?

At the same time that whisker movements appear, motor neurons receive a set of inputs from an area of ​​the brain stem called LPGi. Each LPGi neuron is connected to motor neurons on both sides of the face, placing them in perfect positions to synchronize the movements of the left and right antennae.

To learn more about the newly formed circuits between LPGi and motor neurons, Wang and Takatoh entice the participation of colleagues Richard Mooney, PhD, neurobiology professor, and students of Mr. Anders Nelson. Together, the researchers were able to record labeled nerve cells and found that LPGi neurons communicate with motor neurons using glutamate, the major neurotransmitters. brain stimulation. They also found that LPGi nerve cells receive input directly from the motor cortex.

"This is significant because whiskers are an active movement under the control of the motor cortex ," Wang said.

"Easy-to-stimulate inputs are needed with the onset of such a movement, and LPGi plays an important role for transitional signals from the motor cortex to bearded motor neurons" .

Researchers will then explore connections using genetic, viral and optical tools to see what happens when certain components of the circuits are activated or silenced in the Different advocacy tasks.

In addition to Wang, Takatoh, Mooney and Nelson at Duke, other authors of the study include Zhou Xiang of the University of Chicago, Michael D. Ehlers of Pfizer Inc R&D; M. McLean Bolton of Max Planck Institute, and Benjamin R. Arenkiel of Baylor Medical School.

The study is supported by grants from the National Institutes of Health (DA028302, DE19440, NS079929) and Duke's Brain Science Institute.