What scientists know for certain about the teenage brain?	How scientists interpret these facts?	What scientists still want to learn about the teenage brain?
Rates of death by injury between ages 15 to 19 are about six times that of the rate between ages 10 and 14. Rates of death by injury between ages 15 to 19 are about six times that of the rate between ages 10 and 14. The volume of gray matter which is where thought and memory take place peaks in early adolescence.	There are a lot of factors influencing the development of the teen brain: experience, biological changes, environment Controlling impulses and planning are among the last parts of the teen brain to mature. Scientists believe that the loss of synapses as a child matures is part of the process by which the brain becomes more efficient. Although genes play a role in the decline in synapses, animal research has shown that experience also shapes the decline. Synapses "exercised" by experience survive and are strengthened, while others are pruned away.	The significance of the adolescence period on lifelong mental health. Scientists are working to determine to what extent the changes in gray matter on brain scans during the teen years reflect growth and pruning of synapses.