The human brain
is a three-pound mass of pinkish gray tissue—and the most complex living structure known
. Its intricate network of more than 100 billion nerve cells
controls all voluntary and most involuntary activities. The large prefrontal cortex
is where reasoning and planning takes place. Other brain structures help you see, hear, smell, taste, and touch the world around you, enable memory
and learning, and keep your heart pumping and lungs working. Your life depends on the intricate coordination of all of these parts
Your brain is divided into two halves, or hemispheres. A deep groove runs down its center, separating the two hemispheres. Each hemisphere is almost a mirror image of the other but each has a slightly different pattern of bumps and grooves. And each hemisphere controls the opposite side of the body and is associated with different functions. The left hemisphere is specialized for speech, writing, language, and calculation. The right hemisphere is specialized for spatial abilities, face recognition, and some musical abilities.
The corpus callosum is a thick bundle of nerve fibers that connects the two hemispheres of the brain. It allows the two hemispheres to communicate, which is important for coordinating left- and right-brain functions.
The cerebrum is the largest part of the brain and controls all conscious thoughts, experiences, and actions. It is divided into right and left hemispheres, which are joined by the corpus callosum. Its outer folded layer is called the cerebral cortex.
The cerebral cortex is the folded gray tissue that covers the surface of each cerebral hemisphere. It is responsible for language, music, calculations, imagining, thinking and planning. It controls our ability to move our arms, legs, head, eyes, tongue—any body part we can move deliberately. It determines our intelligence, emotions, and personality. It also processes sensory information for vision, hearing, and speech. Almost everything we do consciously depends on the cortex.
The frontal lobes are located behind the forehead. This area of the brain is associated with higher-level thinking, such as problem solving, reasoning, and some aspects of speech. It also contains the motor cortex, which controls voluntary movement.
The temporal lobes, above the ears, are involved in hearing,identifying objects, understanding language, and storing memories. They also play a role in emotions.
The parietal lobes
on the top of the head process senses
like touch, pain, temperature, pressure, and spatial awareness
. They are also associated with voluntary movement, attention, language, and some mathematical abilities
The occipital lobes at the back of the brain interpret visual information like color, light, shape, and movement. The left and right occipital lobes interpret messages from the opposite halves of each eye. For example, the left occipital lobe receives visual signals from the left half of the retinas in both the right and left eyes, and these halves, in turn, see objects in the opposite (right) halves of the visual field. The two lobes are connected, so the information is combined to produce a single image.
The prefrontal cortex in the forward part of the frontal lobe helps control the highest levels of thinking, such as planning, reasoning, and imagination. It is also involved in conscious functions such as empathy, self-perception, and the ability to interact appropriately with others. This part of the brain is especially well-developed in humans.