The human brain has 100 billion neurons; each one of these neurons are connected to many other neurons. One neuron may have as many as 20,000 connections; there is between 100 trillion and 500 trillion neural connections in the adult human brain. There are many different parts or 'regions' of the brain. To complete a task - like recalling a memory - usually more than one region of the brain is involved, and they are connected by neural networks which is like the brain's wiring. It is believed that there are problems with the brain's wiring in schizophrenia.