For bipolar in adults, I think there's pretty good agreement about what this looks like. For bipolar in children, there is some considerable debate about where are the boundaries. At the mild end, are these just kids who are active? Is this the class clown at the very severe - is this something other than a mood disorder?
Neuroscientists talk a lot about brain circuits. In fact, the word 'circuit' is probably misleading. We do not know where most circuits begin and end. And unlike an electrical circuit, brain connections are heavily reciprocal and recursive, so that a direction of information flow can be inferred but sometimes not proven.
Most of our brain cells are glial cells, once thought to be mere support cells, but now understood as having a critical role in brain function. Glial cells in the human brain are markedly different from glial cells in other brains, suggesting that they may be important in the evolution of brain function.
Nearly every business collects metrics on inventory, sales, and workplace process. Health care has been slow to measure these kinds of outcomes. Increasingly, general medicine, via either managed care or large practice settings, is improving by collecting data through electronic records and refining practice based on what works.