Marine snail's neural network sheds light on the basis for flexible behavior

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Marine snail's neural network sheds light on the basis for flexible

behavior

http://www.medicalnewstoday.com/medicalnews.php?newsid=31840

From snail to man, one of the hallmarks of the brain is the ease with

which behavioral variants are generated--for example, humans can

easily walk with different stride lengths or different speeds. By

studying how a relatively simple motor network of the marine snail

Aplysia produces variants of a particular feeding behavior,

researchers have found that the ability to generate a large number of

behavioral variants stems from the elegant hierarchical architecture

of the brain's motor network.

Most motor systems are organized into a hierarchy of at least two

layers of neurons, with higher-order neurons acting on lower-order

neurons, which form a small number of building blocks or modules that

produce a variety of behaviors. However, it was not clear how

variants of a single motor act are generated in such a hierarchical

system.

In the new work, Jian Jing and Klaudiusz Weiss of the Mount Sinai

School of Medicine in New York studied the feeding network of

Aplysia, which exhibits a biting behavior in response to the presence

of food. The researchers showed that within the feeding network, two

higher-order neurons that are active during biting behavior employ a

combinatorial mechanism to produce variations in one particular

movement parameter of the biting behavior. The researchers showed

that, tellingly, these higher-order neurons accomplish their roles

through their specific actions on two groups of lower-order

interneurons that directly influence the particular biting-behavior

movement parameter. Therefore, in this system, and likely others, the

generation of large numbers of behavioral variants is characterized

by higher-order neurons that flexibly combine an " alphabet system " of

outputs that are generated by lower-order modules within the brain's

motor network.

The researchers included Jian Jing and Klaudiusz R. Weiss of Mount

Sinai School of Medicine in New York, NY. This work was supported by

grants from National Institute of Mental Health.

Jing et al.: " Generation of Variants of a Motor Act in a Modular and

Hierarchical Motor Network. " Publishing in Current Biology, Vol. 15,

1712-1721, October 11, 2005. DOI 10.1016/j.cub.2005.08.051

http://www.current-biology.com