“After stimulating the cortex of patients undergoing brain surgery for epilepsy, Dr. Penfield asked the patients what they felt.  By observing the location on the brain that caused patients to feel sensations on different parts of their bodies, Dr. Penfield was able to draw a map of the brain. As you can see in this figure above, even though the arms and trunk make up most of your body, they are not given much cortical tissue. However, the face and hands take up a good portion of the primary somatosensory cortex. This is because the amount of primary somatosensory cortex is directly related to the sensitivity of a body area and the density of receptors found in different parts of the body. The areas of skin with the higher density of receptors (like the face, hands and fingers) have more cortical tissue devoted to them. If you were “built” in proportion to the amount of cortex devoted to each part of your body, you would look a bit distorted:  you would have a big head and hands and a small torso and tiny legs.  This distorted body map is called a homunculus which means “little man.”“