Thursday, 29 Jan, 2009 Health & Fitness
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Brain Hemispheres Make War For Neurons

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The majority of animals, including human beings, have an unequal division of functions between the 2 brain hemispheres. One part of the functions is carried out by the right hemisphere and the other part – by the left one. But it isn't that simple since the hemispheres are involved in a real "war" in order to obtain one or another responsibility.

This theory works in a species of fish, called Danio.

During the study of scientists from the University College of London on the brain development in the fish embryos, the biologists found that the "war for neurons" is responsible for at least a part of the asymmetry.

Scientists know that the cells of the nervous tissue of a brain in process of growing can move at big distances. It turned out that the removal of the neurons between the hemispheres is conditioned by the protein Fgf8. It attracts the maximal number of nervous cells on its side like a magnet.

As a result, neurons in different halves of the brain are different in type and binding, "though the absolute quantity of nervous cells is practically the same on both sides", according to Professor Stephen Wilson, the lead researcher.

The protein Fgf8 is present in the both hemispheres and attracts neurons of a certain type. "But this war is not led fairly since in the left hemisphere of the brain Fgf8 has an accomplice", says Jenny Regan, one of the participants in the research.

Another protein, called Nodal, helps the first protein win the battle. It also happens that the activeness of this protein is lowered and then the war is a little bit fairer.

Perhaps, this removal of the cells as a consequence of their attraction by one of these 2 proteins determines the hand with which the person will write. It is known that left-handed people make 10-12 percent of the planet's population. If we suppose that the same processes that happen in the brain of Danio take place in the human brain too, then the conclusion is: the presence of auxiliary factors in the left hemisphere determines whether the person will be left- or right-handed. This is why there are more right-handed people on Earth (the left hemisphere of the brain is responsible for the right half of the body).

If there was no protein Nodal, the war would be fair and there would be an equal number of right- and left-handed people.

But no matter how much we tend to equality and symmetry, nature has its own answer to this, scientists say. Brain asymmetry is necessary and it has a logic explanation.

The other functions of the organism do not depend on one's writing hand (a part of them is inherited by certain areas of the brain, another part is obtained with the ageing of the person, the third part is divided in a jumble).

Throughout evolution, the brain has divided its functions with the aim of preventing conflicts for an efficient information processing by both hemispheres simultaneously.

This discovery will help learn more about the activity of the brain, and it is valuable not only for fish, but also for more complicated human beings, researchers consider. Take for example the fact that some scientists tend to link the development of schizophrenia with the insufficient asymmetry of the brain.

Posted by summer_rain

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