Yale Researchers Describe Human Brain Development

Gene activity governing key regions of the brain isn't same during early development. Some genes, with intricate patterns, become dormant in childhood and resume activity only during teenage, researchers have found.

Yale researchers describe brain development to be a carefully orchestrated symphony with "three distinct movements."

For the study, researchers at Yale looked at the gene activity in cerebral neocortex- a thin layered structure surrounding the mammalian brain. The neocortex is associated with perception, behavior and cognition. Researchers looked at the gene activity in this region at different periods of time - before birth, during childhood and before teen age.

Their study showed that gene activity is quite high during the first six months after conception. Then, by the third trimester, there is a lull in genetic activity. Most of the genes associated with neocortex are hushed.

The brain simply spends time connecting various regions of itself largely during childhood.

Genetic activity resumes during late childhood/early adolescence. This is the time that the brain actually shapes itself and takes up more complex tasks. The entire process involves synchronization of various brain regions. Any disruptions in these connections during early years lead to long term disabilities.

Previous research has shown that several neural connections formed during childhood, get pruned during teenage years. This 'gardening of the brain connections,' starts early in girls than boys.

Nenad Sestan, professor of neurobiology at Yale's Kavli Institute for Neuroscience and senior author of the study, says that the study reveals the "hour glass" shape of human brain development activity; a period of low genetic activity sandwiched between periods of higher gene expression.

Also, this "hour glass" shape wasn't found in monkeys, suggesting that this pattern of genetic activity plays a crucial role in shaping exclusive human brain features.

According to researchers, the human brain is more like a community than a single building. It spends more time connecting various neighborhoods before taking up complex missions.

"The neighborhoods get built quickly and then everything slows down and the neocortex focuses solely on developing connections, almost like an electrical grid," said Sestan in a news release.  "Later when these regions are synchronized, the neighborhoods begin to take on distinct functional identities like Little Italy or Chinatown."

The study is published in the journal Neuron.