Researchers studying disorders of brain development or degeneration have gained a new standard in understanding normal development as a decade-long project that obtained serial magnetic resonance images from people age 4 to 21 years is finished, according to an article in the May 17th online issue of the Proceedings of the National Academy of Sciences.

The researchers scanned the same 13 healthy children and teens every 2 years over a total of 10 years. After co-registering the scans with each other, using an intricate set of brain anatomical landmarks, they visualized the ebb and flow of gray matter in maps that, together, form the movie showing brain maturation from ages 5 to 20 years.

When the investigators produced a time-lapse 3-dimensional movie, it revealed gray matter diminishing over time in a back-to-front wave. This may reflect degeneration of unused neuronal connections during the teen years. Different regions of cortex were seen to mature at the age range in which relevant cognitive and functional developmental milestones occur. The sequence of maturation also roughly parallels the evolution of the mammalian brain, suggested the authors.

Dr. Judith Rapaport, a coauthor of the study, commented "To interpret brain changes we were seeing in neurodevelopmental disorders like schizophrenia, we needed a better picture of how the brain normally develops."

The new study found that the first areas to mature (e.g., extreme front and back of the brain) are those with the most basic functions, such as processing the senses and movement. Areas involved in spatial orientation and language (parietal lobes) follow. Areas with more advanced functions -- integrating information from the senses, reasoning and other "executive" functions (prefrontal cortex) -- mature last.

In a related study published a few years ago, Rapaport and colleagues discovered "an exaggerated wave of gray matter loss" in teens with early onset schizophrenia. The teens, who became psychotic prior to puberty, lost four times the normal amount of gray matter in their frontal lobes, suggesting that childhood onset schizophrenia "may be an exaggeration of a normal maturation process, perhaps related to excessive synaptic pruning," note the researchers. By contrast, children with autism show an abnormal back-to-front wave of gray matter increases, rather than decreases, suggesting "a specific faulty step in early development."

The graphic "Time-Lapse Imaging Tracks Brain Maturation from ages 5 to 20" is available at
http://www.nimh.nih.gov/press/prbrainmaturing.cfm#timelapse
.
A Time-lapse Imaging movie is available at
http://www.nimh.nih.gov/press/prbrainmaturing.mpeg.