Epilepsy is a disease of abnormal brain activity that causes recurrent seizures. Seizures are sudden, brief episodes of altered states of consciousness, often accompanied by spasmodic or unusual motor activity. For centuries, their frightening and violent quality made objective analysis of their nature difficult.

In ancient Greece, the cause of epilepsy was usually thought to be supernatural--the Greeks felt it to be an affliction of the gods. Indeed, the name for the disease comes from the Greek epilepsis, which means "a taking hold" in the sense that a great power might take over someone's body. Because epilepsy was believed to be a "sacred disease," its interpretation was put into the hands of religious adepts who administered an assortment of ineffective remedies such as tortoise blood or camel hair. Their practices were attacked as fraudulent in the fifth century by the Hippocratic school of thought and Greek physicians who...