Hockenbury Discovering Psychology 5th txtbk

A Guided Tour of the Brain69Numerous folds, grooves, and bulges characterize the human cerebral cortex.The purpose of these ridges and valleys is easy to illustrate. Imagine a flat, three-footby three-foot piece of paper. You can compact the surface area of this piece of paperby scrunching it up into a wad. In much the same way, the grooves and bulges ofthe cerebral cortex allow about three square feet of surface area to be packed intothe small space of the human skull.Look again at Figure 2.13 on page 66. The drawing of the human brain is cutthrough the center to show how the cerebral cortex folds above and around the restof the brain. In contrast to the numerous folds and wrinkles of the human cerebralcortex, notice the smooth appearance of the cortex in fish, amphibians, and birds inFigure 2.14. Mammals with large brains—such as cats, dogs, and nonhumanprimates—also have wrinkles and folds in the cerebral cortex, but to a lesser extentthan humans (Jarvis & others, 2005).Each cerebral hemisphere can be roughly divided into four regions, or lobes: thetemporal, occipital, parietal, and frontal lobes (see Figure 2.16). Each lobe is associatedwith distinct functions. Located near your temples, the temporal lobe containsthe primary auditory cortex, which receives auditory information. At the very backof the brain is the occipital lobe. The occipital lobe includes the primary visualcortex, where visual information is received.The parietal lobe is involved in processing bodily, or somatosensory, information,including touch, temperature, pressure, and information from receptors in the musclesand joints. A band of tissue on the parietal lobe, called the somatosensory cortex,receives information from touch receptors in different parts of the body.Each part of the body is represented on the somatosensory cortex, but this representationis not equally distributed (see Figure 2.17 on the next page). Instead, bodyparts are represented in proportion to their sensitivity to somatic sensations. For example,on the left side of Figure 2.17 you can see that your hands and face, which arevery responsive to touch, have much greater representation on the somato sensory cortexthan do the backs of your legs, which are far less sensitive to touch.The largest lobe of the cerebral cortex, the frontal lobe, is involved in planning,initiating, and executing voluntary movements. The movements of different bodyparts are represented in a band of tissue on the frontal lobe called the primary motorcortex. The degree of representation on the primary motor cortex for a particularbody part reflects the diversity and precision of its potential movements, astemporal lobeAn area on each hemisphere of the cerebralcortex near the temples that is the primaryreceiving area for auditory information.occipital lobe(ock-SIP-it-ull) An area at the back of eachcerebral hemisphere that is the primaryreceiving area for visual information.parietal lobe(puh-RYE-et-ull) An area on each hemisphereof the cerebral cortex located abovethe temporal lobe that processes somaticsensations.frontal lobeThe largest lobe of each cerebral hemisphere;processes voluntary muscle movementsand is involved in thinking, planning,and emotional control.Figure 2.16 Lobes of the Cerebral CortexEach hemisphere of the cerebral cortex canbe divided into four regions, or lobes. Eachlobe is associated with distinct functions.The association areas, shaded in purple,make up most of the cerebral cortex.Parietal lobePrimary motor cortex(on frontal lobe)controls voluntarymovementSomatosensory cortex(on parietal lobe)receives informatioon aboutbody sensationsFrontal lobeOccipital lobePrimary auditory cortex(on temporal lobe)processes auditoryinformationPrimary visual cortex(on occipital lobe)processes visualinformationTemporal lobeAssociation areas(on all four lobes)combine sensory and motorinformation; coordinateinteraction among differentbrain areas