The neocortex is made up of several sections. Use the figure 3 to reference these sections as you read more about them.

Cerebral Cortex

The largest part of the brain is called the cerebrum, which comprises about 90 percent. The word cerebrum, in fact, comes from the Latin word for brain. The cerebral cortex is actually the gray, wrinkled surface encompassing the cerebrum. The cerebral cortex looks wrinkly because of its many folds.

Although it is about as thick as corrugated cardboard, if you laid it out flat, the cerebral cortex could almost cover the top of your kitchen table. There are 10-to-14 billion neurons contained within the cerebral cortex, a whopping number when you consider that the world's human population is less than that!

Cerebral Lobes

Nestled beneath the cerebral cortex are the central lobes of the brain. There are four of them, and they are responsible for critical daily activities such as hearing, vision, speech, and executive function.

The frontal lobe is divided into four functional areas:

1. The primary motor cortex is involved in the initiation of voluntary movements. It is composed of the precentral gyrus.
2. The premotor area is made up of the remainder of the precentral gyrus and is also important in the initiation of voluntary movements.
3. Broca's area, located primarily in the left cerebral hemisphere, is important in the production of speech and written language.
4. The prefrontal cortex comprises the remainder of the frontal lobe. It is involved in what may be described as personality, insight, and foresight.

1. The postcentral gyrus is concerned with the initial cortical processing of tactile and proprioceptive (sense of position) information.
2. Much of the interior parietal lobule of one hemisphere (generally the left), together with portions of the temporal lobe, is involved in the comprehension of language (Wernicke's Area).
3. The remainder of the parietal cortex subserves complex aspects of orientation of the individual in space and time.

1. A small area of the temporal lobe is the primary auditory cortex.
2. The parahippocampal gyrus and hippocampus, as part of the limbic system, are involved in emotional and visceral responses.
3. The temporal lobe is involved in complex aspects of learning and memory recall.

The occipital lobe is more or less exclusively concerned with visual functions. Primary visual cortex is contained in the walls of the calcarine sulcus and some of the nearby cortex. The remainder of the lobe is referred to as a visual association cortex that is involved in higher-order processing of visual information.

Still More Cerebral Cortex

The cerebral cortex also contains major internal structures (some of which you've probably heard of) such as the:

• Forebrain: credited with the highest intellectual functions of thinking, planning, and problem solving
• Hippocampus: involved more directly in memory formation and retrieval
• Thalamus: serves as a relay station for virtually all the information coming into the brain
• Hypothalamus: contains neurons that serve as relay stations for internal regulatory systems, monitoring information coming in from the autonomic nervous system

Another Brainy Factoid

The sperm whale may triumph by having the biggest brain, but who wins the pea-brain competition? Stegosaurus, also known as the "plated lizard," roamed the United States 150 million years ago and weighed in at a mighty two tons. And how large was the massive brain that this creature needed to orchestrate its existence? Smaller than a ping-pong ball!