Our brains are divided into many different regions that serve different functions. For example, your eyes are directly connected to several specific parts of your brain. These areas connect to several other brain regions called "visual cortices," all of which connect to other regions in turn. Each of these brain regions receives visual information from your eyes, but does different things with that information. For example, some areas in the visual cortices are devoted to detecting the direction in which objects are pointing, or are specifically tuned to detect movement. Other parts of your brain then weave all this information back together to create "what you see."

Similarly, there are brain regions devoted to each of your other senses, regions to control body movements, regions to manipulate memory, regions for language. These regions can be further subdivided; one region of your brain that detects touch, for example, is organized sort of like a map of your body (called a homunculus), except that proportionately more brain area is devoted to touch in especially sensitive regions like fingers and lips. (In fact, this is partly why your fingers and lips are more sensitive to touch than, say, your leg. Try reading Braille with your leg!).

Recently, medical imaging technologies that measure activity in people's brains without surgery have enabled scientists to answer questions like "what parts of the brain are especially active when performing a complex memory task?", "what parts are most active during different types of sleep?", or even "what parts are active during recognition of a particular brand of car?" These techniques can help scientists better understand how the different regions of the brain work together to create the complex web of sensation, experience, and knowledge that we all enjoy. They also demonstrate clearly that every region of the brain lights up for something.

Where did the "10% myth" first come from? It isn't clear. It might be because less than 10% of the cells in our brains are actually neurons (nerve cells) - the rest are called glial cells. Glial cells perform all kinds of different tasks, from insulating the brain's "wires" to maintaining the brain's chemistry to helping regulate the many connections among neurons (called synapses) in which memory can be stored. Glial cells aren't neurons, but they are certainly being used! The myth could also have arisen because much of the brain is fairly adaptable, allowing people (especially young people) to recover most of their capabilities even after losing parts of their brains to injury, cancer, or surgery. This isn't always true, however; it is harder for older adults to recover function after brain injury, and we know that even small amounts of brain damage (such as strokes) in just the wrong places can be devastating.

So take care of your brain! You'll need all of it.