Sunday, June 3, 2012

Unused brain cells get eaten

When it comes to the brain, it is 'use it or lose it'. That became especially clear when a group of scientists recently demonstrated that those who do not do a lot of thinking, or to be more precise, do not have a cognitive lifestyle, lose their brain cells much faster. Now, researchers from Boston Children's Hospital have found something that might explain why our brains deteriorate faster if they are not used. The immune system appears to eat the neural cells that are not used anymore. Basically, that means 'use it or get eaten', when it comes to the brain.

Throughout our life, the brain constantly forms new connections between individual neurons. Because of that, it is basically a large collection of wires. It also means that throughout life, some connections become obsolete, and are therefore abolished: nothing in the brain gets wasted, which also means that the common saying that you only use 10 percent of your brain is untrue: we use everything, and if there is something that is no longer functioning, it disappears.

At Boston Children's Hospital, scientists discovered that immune cells called microglia, that are only active in the brain, are responsible for clearing away neurons and their associated connections when they are no longer necessary. They observed that by researching mice in which one of the two eyes was artificially made to be less active. In consequence, that means one of the eyes sent less signals to the brain. The scientists showed that the less active eye showed a higher degree of missing brain cells and connections, even though there was no evidence of real damage. Because of that, it became clear that the body had a way of disposing of unused neurons. By looking at the tissue after death, they found that microglia were actually eating the inactive parts.

Furthermore, the researchers discovered what made the microglia eat the inactive wiring. Apparently, it has something to do with the so-called complement system. It is basically a system of molecules, part of the immune system, that slowly builds up. A molecule called C3 is constantly deposited on each and every cell in the body, but also readily transported away again. However, inactive neurons showed a build-up of C3, which is basically a signal for immune cells. According to the scientists, C3 is an 'eat me' signal for microglia.
C3 binds to the membrane of a cell, and gets split into C3a, which  is a chemical signal to attract immune cells, and C3b, which sits on the cellular surface and functions as a target. Normally, C3 would not 'stick' to healthy cells, but only to 'foreign' things such as bacteria. The whole complement system is much more complex, and eventually leads to the formation of a complex that attacks the cell it is attached to.
Science has shown the importance of having a cognitive lifestyle, which basically means we need to use our brains for thinking. Having a less active cognitive lifestyle appears to have its consequences: your brain gets eaten from the inside. A good scientist keeps thinking and keeps questioning; it seems that is something we should all adopt, for our own health's sake.'

1 comment:

  1. Thanks for this wonderfull and knowledgable information.
    now i know the importance of studies.
    thank you!!!!