ABSTRACT
To understand how drugs change the brain, it helps to first understand how the brain works under normal circumstances. So let’s focus on you and your brain.
You live in a complex, ever-changing world. Your brain must keep you alive and functioning effectively in this world. For instance, your brain tells your heart to beat at a speed that is healthy for you and tells your lungs to supply you with oxygen to keep you going. It also makes it possible for you to see, hear, and feel what is taking place around you and then uses this information to guide your actions. What’s more, all these conditions change moment by moment. Your brain must constantly monitor them so that you can constantly adapt to them.
