Brain cells are a bit like tadpoles. The main body of the cell has a long tail called an axon which carries signals from one cell to another. Axons are lined with a fatty substance called myelin which helps to conduct nerve signals; the thicker the myelin the better the conduction and the more quickly people are able to process information. Researchers from the University of California, Los Angeles used a new type of brain scanner to look into the links between people's genes and the quality of their myelin covering in their brain. They scanned 23 pairs of identical twins (whose genes are exactly the same) and 23 pairs of non-identical twins, who share about half their genes. This enabled the researchers to assess to what extent the genes affected the myelin covering. They found that myelin quality was determined genetically in many important parts of the brain including those responsible for spatial reasoning, visual processing and logic.
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