These anatomic changes are consistent with electroencephalographic, functional MRI, postmortem, and neuropsychological studies indicating an increasing “connectivity” in the developing brain. “Connectivity” characterizes several neuroscience concepts. In anatomic studies connectivity can mean a physical link between areas of the brain that share common developmental trajectories. In studies of brain function, connectivity describes the relationship between different parts of the brain that activate together during a task. In genetic studies it refers to different regions that are influenced by the same genetic or environmental factors. All of these types of connectivity increase during adolescence. A linguistic metaphor would be to consider the maturational changes not so much as adding new letters to the alphabet as combining existing letters into words, those words into sentences, and the sentences into paragraphs. Characterizing developing neural circuitry and the changing relationships amongst disparate brain components is one of the most active areas of neuroimaging research utilizing graph theory to quantify such things as small world network properties of the brain.
