Some teens will take offense to the idea that they are losing their frontal gray matter - and the figure below suggests that white matter in the deep brain structures is actively increasing.
What it does mean is that a whole lot is going on in young growing brains. It would also seem to be an ideal time to organize growing connections by training attention and cognitive control.
The striatum is important for early learning, cognitive control, and reward. It also has a differential pattern of activation in individuals diagnosed with ADHD.
Teen Brain: Less Frontal Gray Matter or More White?
Eide Neurolearning Blog: Obsessions and the Will - Frontal-Striatal Circuits
Eide Neurolearning Blog: Deep Brain Structures (Striatum) Quickest to Learn?
Eide Neurolearning Blog: ADHD is Not a Simple Deficit Disorder