some neurons are much farther away from the prefrontal cortex than others

The problem is that some neurons are much farther away
from the prefrontal cortex than others.If the signals travel down both fibers at the same rate,they'd arrive out of sync.You can't change the length of the connections,but your brain, especially as it develops in childhood,does have a way to change the conduction velocity.Neural fibers are wrapped in a fatty substance called myelin.Myelin is an insulator and speeds up the electrical signals zipping down the nerve fiber.