Scientists Discover “Hour Glass” Shape of Human Brain Development Over Time

Nenad Sestan, M.D., Ph.D., Expert brain researcher
Nenad Sestan, M.D., Ph.D.

A team of researchers from Yale School of Medicine has discovered how and when a primary section of the human brain develops at different stages from conception to adulthood. Led by two-time NARSAD Grantee Nenad Sestan, M.D., Ph.D., the researchers identified an “hour glass” shape of developmental activity through time, with a lull in genetic activity in between two phases of highly complex patterns of gene expression. The research results were reported in the December 26th issue of Neuron.

Dr. Sestan, Professor of Neurobiology at Yale’s Kavli Institute for Neuroscience, and his team conducted a large-scale analysis of gene activity in the cerebral neocortex―an area of the brain responsible for perception, behavior and cognition―at different stages of development. They discovered three major phases of development. The first phase occurs during prenatal development and is characterized by the highest number of differential expressed genes. The second phase, during preadolescence, showed fewer gene expression differences and more synchronization between developing areas. This is a quieter intervening "movement" in the three-part "symphony" of human brain development, the researchers report, but one that is more sensitive to environmental factors. The third phase, from adolescence onward, saw another rise in differential gene expression in certain predominant areas.

Using language from architectural town planning, Dr. Sestan says that while the first, most active phase of brain development creates the basic structure of the "neighborhood" of the human brain, it is better defined by the "community" living within it, developed more slowly during the childhood phase. "The neighborhoods get built quickly and then everything slows down and the neocortex focuses solely on developing connections, almost like an electrical grid. The third phase can be compared to identities developing in geographical places,” Dr. Sestan offers. “Later, when these regions are synchronized, the neighborhoods begin to take on distinct functional identities, like Little Italy or Chinatown."

By better understanding this “symphony” of brain development in the early years of life, scientists may be able to predict, treat or develop early intervention techniques for mental illnesses that may develop during childhood and adolescence. “For instance, disruptions in synchronization of synaptic connections during a child’s earliest years have been implicated in autism,” says Dr. Sestan.

Learn more about this research in a press release from Yale.

Read the abstract of this research.