Two parallel computers.

Our brain has two hemispheres, which are like two computers set in parallel.  If you have two "Pentium 5", you get double power.  But, if you've got a new "Pentium 5" on one side and an old "Commodore 64" on the other, you've got problems.  The old computer is not fast enough to keep up with the new one.  The system bugs.  That's what is happening in the ADHD brain.  The delayed hemisphere is weaker, which leads to communication problems within the brain resulting in symptoms of inattention, impulsivity and hyperactivity.