It's no accident that telephone numbers in the United States are seven digits long. Our working memory, a very short-term form of memory which stores ideas just long enough for us to understand them, can hold on average a maximum of seven digits. This allows you to look up a phone number and remember it just long enough to dial.

0.5% of the general population has epilepsy. But it is estimated that one in 20 people will have at least one seizure during the course of their life. While seizures are characteristic of epilepsy, having a single seizure does not, in itself, constitute epilepsy. The effects of seizures can vary from complete loss of consciousness to mild shakes or loss of balance.

It has been estimated that about one million people in the United States have acquired aphasia. Aphasia is an impairment of the ability to use or comprehend words, usually acquired as a result of a stroke or other brain injury. There are several different types of aphasia depending on the location of the brain injury. There is currently no drug treatment for aphasia although surgery and speech therapy are sometimes successfully used as treatment.

There is no sense of pain within the brain itself. This fact allows neurosurgeons to probe areas of the brain while the patient is awake. Feedback from the patient during these probes is useful for identifying important regions, such as those for speech, that are spared if possible.

Although the brain accounts for only 2% of the whole body's mass, it uses 20% of all the oxygen we breathe. A continuous supply of oxygen is necessary for survival. A loss of oxygen for 10 minutes can result in significant neural damage.

Approximately 20% of the blood flowing from the heart is pumped to the brain. The brain needs constant blood flow in order to keep up with the heavy metabolic demands of the neurons. Brain imaging techniques such as functional magnetic resonance imaging (fMRI) rely on this relationship between neural activity and blood flow to produce images of deduced brain activity.

Strokes or "brain attacks" are the 3rd leading cause of death in the United States. A stroke occurs when the blood flow to the brain is disrupted. Disruption takes place either when a brain artery is blocked or when an artery explodes. Recently, exciting medical breakthroughs have been announced with respect to treating stroke.

The effects of a stroke depend on the affected blood vessel and the area of brain that it supplies with nutrients. For instance, if the middle cerebral artery is occluded, motor areas in the frontal cortex can be damaged resulting in the loss of voluntary muscle movements on the contralateral, or opposite, side of the body from the damaged side of the brain. This condition is known as hemiplegia.