The
Human brain has the same general structure as the
brains of other
mammals, but has a more developed
cerebral cortex than any other. Large animals such as whales and elephants have larger brains in absolute terms, but when measured using the
encephalization quotient, which compensates for body size, the human brain is almost twice as large as the brain of the
bottlenose dolphin, and three times as large as the brain of a
chimpanzee. Much of the expansion comes from the cerebral cortex, especially the
frontal lobes, which are associated with
executive functions such as
self-control,
planning,
reasoning, and
abstract thought. The portion of the cerebral cortex devoted to vision, the
visual cortex, is also greatly enlarged in humans.
The human cerebral cortex is a thick layer of neural tissue that covers most of the brain. This layer is folded in a way that increases the amount of surface that can fit into the volume available. The pattern of folds is similar across individuals, although there are many small variations. The cortex is divided into four "lobes", called the frontal lobe, parietal lobe, temporal lobe, and occipital lobe. (Some classification systems also include a limbic lobe and treat the insular cortex as a lobe.) Within each lobe are numerous cortical areas, each associated with a particular function, including vision, motor control, and language. The left and right sides of the cortex are broadly similar in shape, and most cortical areas are replicated on both sides. Some areas, though, show strong lateralization, particularly areas that are involved in language. In most people, the left hemisphere is "dominant" for language, with the right hemisphere playing only a minor role. There are other functions, such as spatiotemporal reasoning, for which the right hemisphere is usually dominant. (Full article...)
