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April 2000Vol. 1, No. 2New Glossary Defines Brain Development

Emerging research in neuroscience points to the first 3 years of life as crucial to a child's healthy physical, emotional, and intellectual development. The new "BrainWonders" website, sponsored by Zero to Three, serves as a resource for parents, caregivers, and pediatric/family clinicians on early brain development.

A glossary, featured on this site, defines the parts of the brain and stages in brain development. It also defines processes to measure the brain, such as brain imaging and the electroencephalogram (EEG). Some interesting definitions are:

  • Brain: A baby's brain triples its weight in the first few years of life and quadruples in size by the time a child becomes an adult. Most of this gain is not due to addition of new brain cells (neurons), but rather, to increased complexity and interconnections among the brain cells that we are born with, as well as to increases in the supporting cells.
  • Pruning: A process in brain development whereby unused brain cells, or unused synapses (connections among brain cells), are shed. At about 2 years, a child's brain compared with an adult brain has about twice as many connections among neurons. By the teenage years, those not in use are shed. Only those that are put to use survive.
  • Windows of Opportunity: Scientists believe that there are "sensitive periods" of time when the brain is capable of learning most efficiently and thoroughly... For example, children develop a "native accent" in a language if they begin to hear and speak it when very young. Someone who learns a new language at 3 years old will sound more "native" than one who begins as a 10-year-old. Around puberty, the "window" for easily acquiring native accents may close, for most people. Studies show little difference in the accent of someone who learns a new language as a teenager in high school, compared to someone who learns in middle age.

The BrainWonders glossary is available online at

Zero to Three ( is a national, non-profit organization located in Washington, DC, dedicated solely to advancing the healthy development of babies and young children.