The human brain contains an average of ten billion neurons or nerve cells, each of which is linked with one thousand to ten thousand other neurons. These nerve cells participate in countless electrical microcircuits which make possible thought, perception, communication, and other types of mental activity.// The outside surface of the brain, which is known as the cortex, consists of a thin wrinkled mantle of gray tissue made up of millions of neurons. This layer of the brain represents man's relatively recent evolutionary step in neurological development and is not present to a comparable degree in any other species.// The brain is divided into two roughly symmetrical hemispheres, sometimes called right and left brains. The activity of the two hemispheres is coordinated by a number of interconnecting nerve pathways. The two sides of the brain, while fairly comparable in size and form, appear to specialize in handling various tasks.// Current evidence suggests that the left and right hemispheres differ in some way in their function. For example, specialized linguistic and perceptual skills are each associated with a particular hemisphere of the brain. In most individuals, the left hemisphere has primary responsibility for language, while the right hemisphere controls visual and spatial skills as well as the perception of nonlinguistic sounds and musical melodies.//

人的大腦平均有 100 億個神經元，或者叫做神經細胞。每個神經元與其它一千至一萬個神經 員相連。神經元從事著不可悉數的微電路脈沖活動，并由此產生思維，感覺，交流以及一些其他腦力活動。//大腦的外皮層叫做腦皮層，腦皮層很薄，有褶皺，是一層由是一百萬計的神經元組成的灰色組織。腦皮層代表著人類在其神經發展的歷史長河中近期的以此進化，任何其他物質的腦皮層都無法和人類的腦皮層相提并論。// 整個大腦分為兩個大致對稱的半球，有時被稱為右半腦和左半腦。一些互為聯系的神經束對這兩個腦半球活動進行協調。大腦兩個半球雖然有著相像的尺寸和形狀，卻各司其職。//據目前所知，兩個鬧半球有著不同的功能。例如：語言能力和感知能力隸屬于不同的半球。大多數人的左半球負責語言操作，而右半球則掌管與視覺和空間相關的技能，負責對非語言 聲音以及音樂的感知。//