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TRUTH Read the follovving statements about psy chology. Do you think they are true or false? You will earn whether each statement is true or false as you read the chapter. Individual cells in the human body can be several feet long. Anxiety can give you indigestion. A person with brain damage may be able to report that he or she has seen a face hut may not be able to dentify that it was the face of a close friend. Some people are ‘left-brained” and others are “right-brained.” The father’s genetic contribution —not the mother’s—determines the sex of the offspring. nincle possible iv the nervoi is vstein. \\‘hen we learn a new ieii,t\ br or accjuire less’ ilitornial ion, lie Hers ons s 1eni rt’bi-tei that eeriene i,ih ,hans in iL H mi no Lue im -i orasc. ‘he lit’ ‘St ls s\ 0 ciii Lm i o I R,tI n u ii o i be Ccii toil ners ous oeni and He eriphr’rai nervous s\ s ‘iii, I He central nervous system Ii.it’, 0! brain and tie spinal mi ri ihe peripheral nervous sVStdfll is Iiiarfe rip of ner\ L ells that send near between ihe cent ml nervous ss stem mcl ,iii t lie paa is ol the liod\. In ordei to uiiderstali(l Loss the cciii ml a id I he pr n pH ‘al iv rs ous 0 ems 0 01 l\ se niuo lirt rnirleiianrl Loss Hr rse cells conitnu ii eat e oil h one ai lot her and hose i heir messapes i no I iliroubli t lie liod, Neurons ‘verve ‘e ls, milled neurons, run throuh oui entire 1 indies and eennnin;o,ite o ‘H each oilier Neuron -end and mm ei’ e iness,lbes from oilier st rum i ures in lie hodv. srih as muscles and Hands. [hew CieS I The Nervous Svsiem ‘abes aii aiim i evenb rai’,iiivt Irom die seiisailOii 01 a lim ml 0 eps ot ci l ild I rein he lie memory of a inst e\ ent. Lavh of us has more than I hi) billion it tn’’ns most of ss him Ii are found iii the brain, rcK 0 the I ne of a poem to I I he 1 untiii iie r\ Oils vle iii is I nm ii s ed in bin Liii dreamin, leelinb, ni(’\ ing. ,nicl iuu h more. Ii 0 H Kin ORCR o e nre octis e or t ill, no nl\e or ,isl ep. lb ners ous ss stem rehu Lies our inic mnl smi tions. It is also nvolved m how oe react to I he esienial world, [yen learn n and memors are \vurons ii’m sonic o lint lil\e trees in 0 rilr I ui’e Ru’ts of ie u i’ons reeni He t lie branches. I run Is mu room H ice. .\nd, is The Anatomy of Two Neurons Dendrites Cell body Nucleus Myelin sheath Synapse I’ / Axon FIGURE 3.1 “Messages” enter neurons through the dendrites. These messages are transmitted along the 54 e ti.otLe 3 trunklike axon to other neurons, glands, and muscles. The myelin sheath protects the axon. many nerve c uS ie alonesile one her like a thicket ot trees. L nlike trees. how neurons can also lie end to end. [heir “roots” m ntcrt\vl ned it h the “branches I meurons i hat helow see ligure 3. 1 Lvei’v neoroii consists ot a cll hodv, dendrites, md an axon lie ccli body ii odtmces energy that is the activity of the cell. Branching out from the II bodx are thin tihems called dendrites, the den ites receise molormation from other neuron s and ass the message through the cell body. \Vhiie i lie dendrites carry mnlormation to lie cell the axon carries mimessages uwtIV. .\ neuron has any dendrites hut usualh a mIs one axon, Axons mi-v greatly in length. ‘Nomne are umtst a 1 nv lractmon 1 an mcli. white 01 hers sI reich to several feet. •ccause of’ the B ngth of their axons. sonic neui’ons mm your legs are several feet long. forests. The Synapse ii / Direction of nerve impulse Axon terminal of %—sending neuron ‘• 55 io: NReceptor site Synapse Neurotransmitters It is true that individual ce/Is in the body can be several feet long. These cells are nerve cells, or neurons, that are onn becauw they have ong ii axons. Some of these neurons u are in the leg and are several feet long, stretching from the lower spine to the toes. TRUTH Sacs containing neurotransmitters Dendrite of receiving neuron FiGURE 3.2 There is no physical connection between neurons. A neuron relays its message across a junction called a synapse by releasing chemicals called neuro transmitters. They or received by the next neuron. fictors include the locations of the neuron in the body and the events that proctor ccl the message. I or example. the pam in \larcs toe \s as transmitted to his brain through sen sory neurons. sensory neurons are nerve cells that carry information received by the senses to the cent raf nervous system. Motor neurons, on m lie other hand, are nerve cells that carry infornsa ion I’ urn i lie cc ntral nervous system to the muscles .aid the glands and influence their functioning. Motor neurons took the message to \‘larci toot o that lie pulled up on it and began to rub it. Other motor neurons stimulated March glands , making his heart beat laster, Still other neurons in his brain enabled bins to think over die matter and am decide i hat I’ocld should lie forgiven. ccasionalls something happens to disrupt the nicssage-scnding process. For example. a hard blosv n ii ie hear! irorn a car accident or a ports mnturv can cause a concussion—an inlurv in ss hicli the soft tisstie of the brain hits against tile skull. Sometnnes, the person is affecter! for only a fw seconds. Other times. t lie person may experience etfdcts for a much longer time. In 1993, Dallas Cowboys c uarterback 1 l’rov \ikman i’eceived a concussion during a game in the National Bootball League plax oils. He - \lanv axons are cm erect ss a h rnvelin. a white • tttv substance that insulates and protects the axon. his mx cliii sheath, or casnio, also helps to speed p the transmission of the message. At t lie end of - ic axon. sinai icr fibers branc ii out. These fibors are ailed axon terminals. \lessages aie cut from the axon terminaL of one neuron to the iendrites of ot tier neurons. In order for a message o be sent from one netiron to mother neuron, ii oust cross the synapse. [le s\ napse is a unction het\veen i lie axon ternnnals ol one neuron and the lendrites of anot her neuron. Messages t ras ci in niv one direction, [bus, niessages are received by he dendrttes and travel through the Lil i is and he axon to t lie axon terni nals. F’rons there, they ‘ross c\ napses to the ctcndntes of Other neurons. See Ligure 3 2.) New synapses dan deselop oet\s ccii neurons that were not previously con iterted, as when we learn somethmg new. 1 lie information that is sent and the place to ,vhtch it goes depend on a number of factors, These PtOL(iGY .\Nt) ait I \\ ICR 55 are involved in r lie underlying biological process. In addition, some diseases and psychological cl isor tIers inas be caused hi he pi cseili e of too much or I oo little of s anous neurotr imm titers. Ruscais hers has e ideni died dozens ) iieti ro transmitters and their I uilut ions. For exam P Ic, t eivleholine is a common ncuroi ransiniiter that is ins oh ed in the coni ‘of of muscles. It is used by the motor neurons of t he spinal cord amid sti inn ales skeletal inticetec. I he release of aecr lcholt tie ii as s’ hat dci to \lat’c resDonse 1 eral’btng his loot. I )opatniue is anot her ncuroi ransini it e r. ft is involved primarily in imiotor In Eavioi’. .\ . L’Iiciencs in dopaninc levels plo’. s a sic in Parl\ii Oiis his’ cjse, \\ lid i is char,n u riced bc it-c m us ii id tine - 4% Troy Aikman concussion in the 1993 football playotis interfered with his memory of the event. remembers being at the game, b it he annot remember what happened during the game. teli zxnerienees show that memory is in large part a bio logical process. t See Lhapter 7 oisimated. rigid nlo\cmcnts :\n cnss I dopamumne nay ontribute to the psvcboogcal di on her sclnz 5 pilmumlia. cc 1 hapici S. ihcr imeurntrainnnttci include ioradicnalinc. s’. htcli is pnnntritv ni is cd in ni’cpaiing the bod\ action and ci’Oh}iliil. n lti fitS tivlscd iii cnn total at uisal md cli cp Ii ouch is c are ofti n unaware of the processes iii on noclis sic con he sums that our bodies ire fiord \\ orE ii fmcthci sic are i unnnig or ottmg still. .\t Veurotransmitterc: Chemical Messengers \urons send messages across synapses through dac t elease of neurotransmitters. \eurotrans mitters are chemicals that are stored in saks in the axon terminals. ;\ neuron fires, or sends its messaec, by releasing neui ti-ansrnitters—much like droplets of water shooting out of a spray bottle I his ciii occur hundreds of times ci cry second, There are several types oi nctirotransntitters. Each has its own specific structure and its into a reecotor site in the next neuron, cnni lar to i he \\ a\ n which a key fits into a lock. [he message is e in erteci into an electrical impulse that I ras c Is the ungth of the neuron The message i hun i ranmn d to the next neuron by neurotransmiiiers. EEc li continues until the message arris es ai is icstination. which in many eases is the brain. I its hole process takes only a fraction oi a ser OilLl. curot ransmitters are involved in sen thing 5 neople do. \\‘henever a person \vaves a hand. urns, or ifitnlss about a frencl, neurotrancmittcvs - 0 56 HPP I’ER 3 Long-distance runners experience a “runner’s high,” which may be connected with the release of endor phins. Endorphins are neurotransmitters similar in function to the drug morphine. They have a tranquil izing and painkilling effect on the body. nv given moment, billions of neurons are shooting ic urotransmi tters across synapses and sending omplicated messages to various parts of the body liese messages are carried via the spinal cord and he peripheral nervous system. (‘he central Nervous System igure 3.3 shows the central nervous system, which onsists of the neurons of the spinal cord and the rain. (The brain is discussed in Section 2.) The pina1 cord extends from the brain down the back. It is a column of nerves about as thick as a thumb. tnd it is protected by the bones of the spine, It transmits messages between the brain and the mus Ics and the glands throughout the body The spinal cord is also involved in spinal reflexes. A spinal reflex is a simple. automatic response to something. For example, if a person The Central Nervous System Brain Spinal cord ouches a hot stove, a message goes immediately Irom his or her hand to the spinal cord. A message to remove the hand is then sent back to motor neu rons in the hand. fhe removal of the hand is a spinal reflex. The person may also register pain in his or her brain. But the nam s not what causes the eflex. In fact, the pain may not even be felt until ifter the hand has been removed.) Many of our simple actions are reflexive. Have ou ever wondered why you blink when you get a )peck of dust in your eye? Or why some people neeze when they sniff pepper? Physicians some imes test people’s reflexes to learn whether their iervous systems are functioning properly When a doctor taps just below the knee to see if you kick, he purpose is to check your knee-jerk reflex to make sure your neurons are responding the way hey are supposed to. The Peripheral Nervous System Ihe peripheral nervous system lies outside the cen tral nervous system and is responsible for transmit 1ng messages between the central nervous system and all parts of the body F he two main divisions of he peripheral nervous system are the somatic ncr ous system and the autonornic nervous system. See Figure 3.4 on page 58.) Ehe somatic nervous system transmits sensory messages to the .entral nervous system. It is activated by touch, ain. changes in temperature, and changes in body ,osition. The somatic nervous system enables us to 5 II FIGURE 3.3 Your spinal cord is protected by a col umn of bones ca/led vertebrae. Similarly, your brain is protected by the skull, BIOLOGY AND BEHAVIOR 57 (4 moved or liiiieed position. It sends messages to the muscles nid lie :la1Rls and helps us maintain posture and balan e. The word autonoinic means “occurring involuntarily,’ or auto matically. The autonomic nervous system regulates the body vital lunctions, such as heartbeat, breath ing, digestion, and blood pressure. We generally do not have to think about these activities—they occur automatically and are essential for keeping us alive. Psychologists are interested in the autonomic nervous system because of its involvement in the experience of emotion. The response of the auto nomic nervous system is particularly important when a person experiences something stressful in the environment. The autonomic nervous system has two divi sions: the sympathetic and the parasympathetic nervous systems. (See Figure 3.-f.) These systems generally have opposing functions. The sympa thetic system is activated when a person is going Into action, perhaps because of some stressful event. It prepares the body either to confront the situation or to run away This is sometimes called the “fight-or-flight’ response. For example, when a person is suddenly attacked by a large angry dog, the sympathetic nervous system is aroused. The sympathetic nervous system prepares the body by suppressing digestion, increasing the heart I I When the doctor hits your knee joint, sensory neurons carry the message from the muscles to the spinal cord and the brain. Motor neurons carry a message from the brain back to the muscles, making your leg move. experience the sensations of hot and cold and to feel pain and pressure. For example. we can feel the softness of a cat’s fur, warmth if the cat is sitting on our lap, and pain if the cat scratches us. The somatic system also alerts us that parts of the body have Divisions of the Nervous System [Nervous system Central nervous system Ii Peripheral nervous system I Brain 4 1 I Spinal cord Autonomic system (involuntary muscles and internal organs) Parasympathetic system (calms body after emergencies) FIGURE 3.4 This chart shows the major divisions of the nervous system. The central nervous system consists of the brain and the spinal cord. The peripheral nervous 58 (ZHAPTER3 “-“-. Somatic system (voluntary muscles and sense organs) 4 Sympathetic system (prepares body for action) system transmits messages from the central nervous sys tem to all parts of the body. I id respiration rates, and elevating the blood pres tie. Do you ever feel queasy when you are in a stress ul situation—such as when your teacher springs a ii prise quiz on you? This is because your sympa thetic nervous system has kicked into k action and has suppressed your diges tive processes. And when Todd stepped on Marc’s toe, Marc felt his heart start to race—another result of the activation 1I of the sympathetic nervous system. TRUTH ) R E V S I E D It is true that anxiety can give you indigestion. Anxiety may cause indigestion by induc ing activity of the sympa thetic nervous system, which suppresses digestion. before scientists had learned much about how the brain functions, people did not attribute human psychological processes such as thinking to the working of the brain. People thought that what was inside a person body was not very different from what was inside an animal’s body Therefore, they reasoned, the abilities that make people different from animals—such as creative thought, art, and analytical abilities—could not he explained in bio logical terms. Instead, it was widely believed that the body was inhabited by souls or demons. The ancient Egyptians believed that a little per sOfl dwelled within the skull and regulated behav ior. The Greek philosopher Aristotle thought that the soul had set up living quarters in the heart. B. F Skinner iJ987) noted that the English language still reflects the belief in the heart as the seat of will, thought, hunger, and joy We use expressions such as ‘deep in one’s heart,” “to know something by heart,” look into someone heart,” and ‘to have change heart.” Today. however, that the mind, consciousness, dwells within the brain (Goldman Rakic, 1995; Sperry 1993). We know that when thoughts of Linda ran through Marc’s mind, something was happening in his brain. We now have greater under standing of (he brain and the links between biological processes and psy chological phenomena. “to In contrast to the cmpathetic system, the virasympathetic nervous system restores the body’s eserves of energy after an action has occurred. leart rate and blood pressure are normalized, hreathing is slowed, and digestion returns to nor al, If you are having trouble remembering which ,‘ctem is which, perhaps it will help to keep in nind that “sympathetic” and “stress” both start with he letter s, while “parasympathetic” and “peace” ‘oth begin with p. [he sympathetic system reacts to tress, the parasympathetic system restores peace. a of we recognize or Parts of the Brain HINkING ABOUT PSYCHOLOGY 1. How do messages travel from one neuron to another? 2. Identify the systems that make up the peripheral nervous system. 3. Critical Thinking In what way do the parasympathetic and the sympathetic ner vous systems work together? The Brain: Our Control Center ‘very person is unique in part because of the capac ies for learning and thought made possible by the tuman brain. In ancient times, hundreds of years The human brain is composed of many parts that work together to organize our movements, create our thoughts. form our emotions, and produce our behaviors. rhe brain is divided into three sections: the hindbrain, the midbrain, and the forebrain. (See Figure 3.5 on page 60.) The hindbrain is the lower portion of the brain and is involved in many vital functions such as heart rate, respiration, and bal ance. The midbrain includes areas that are involved in vision and hearing. The forebrain, the front area of the brain, is involved in complex functions such is thought and emotion. i The medulla, the pons, and the cerebellum are important structures of the hind brain. rhe medulla is involved in vital functions such as heart rate, blood pressure, and breathing. The pons is located in front of the medulla and is involved in regulating body movement, attention, sleep, and alertness. BIOLOGY AND BEHAVIOR 59 Parts of the Human Brain FOREBRAIN MIDBRAIN o Reticular activating system (middle part) A Reticular activating system (upper part) A Thalamus A Hypothalamus A Cerebrum Cerebral cortex HINDBRAIN LI Reticular activating system (surface of cerebrum) Corpus callosum (lower part) LI Medulla LI Cerebellum 11 Poris FIGURE 3.5 The average human adult brain weighs about 3 pounds and has more than 10 billion cells, many of which are neurons. Although the brain makes up about ‘ivix’lluni is the Latin word for little brain.’ The cerebellum looks like the larger part of the brain (the cerebrum), tinder which it rests. hut it is much smaller. It is involved in balance and coordi rianon. A person whose cerebellum is injured may have trouble with coordination. [he person may walk unevenly and even occasionally fail doivn. [he midbrain is located between the hindbrain and the forebrain Areas within the midbrain are involi ed in vision and hearing. Eve movement, for example. is controlled by an area in the midbrain. In addition, the midbrain contains part of the reticular activating system. [lie reticu ar activating system begins in the hinclbrain and nes through the midbrain into the lower part of the urchrain. F his system is tmiaortant [or attention. 60 CHAPTER 3 2 to 3 percent of a person’s body weight, it requires about 20 percent of the blood’s oxygen supply. sleep. and arousal. Stimulation of the i’eticular acE ‘:ating system makes us alert. It aflcts arousal by increasing heart rate and blood pressure, and it increases brain activity some drugs, such as alco hol, reduce the activity of the reticular activating system, thus affecting alertness and reaction time. sudden, loud noises stimulate the reticular acti vating system and can awaken a sleeping person. However, the reticular activating system can screen out some noises A person who lives in the city may not he awakened by the sounds of traffic roaring by This same person ma however, awaken to sounds that are more out of the ordinam such as a bird singing, even tf these sounds are fairly soft. Pour motor areas of the fore brain al-c the thalamus. the hypothalamus, the inic s\ stem. and he cerebrum. Certain iaarts of forebrain are very well developed in human ms. T’he forebrain is the part of the brain that \cS it posinie for humans to cige in complex nkmg processes. I lxikuu its is a Latin word meaning ‘inner cham The thalamus is a critical structure of the un because it serves as a relay station for sensory inulation. Most of the messages coming from the use organs go through the thalamus on the way to higher levels of the brain those areas responsi for mental processes such as thinking and [he halamus transmits reas nuii’’ sensory information. Nueh as the pain from \Iarey big toe, to the areas of the brain that interpret and respond to the in format ion, 1 he t halamus also relays senorv input from the eves and the of he brain kr inter to the appropriate .aation of the input Hype- is a rreek prefix neaning “under. “Thus. hypothalamus lies below i he thalamus. [he pothalamus is \ cry tinu hut it is e\tremelv mortani because it is in oh ed in many aspects of havior and physiological functions. it is s ital to regulation ot body temperature, the storage of truents, and various aspects of mol Ration and couon. It is also involved in hunuer. thirst, sexual savior, earing br offspring, and ieression turhances wit hin t lie hypothalamus can lead to usual drinking and eating behaviors, mong lower animals, stimulation of parts of hypot halamus triggers behaviors such as fight 3, mating, or nest building. ,\lthough the hypo 1iamus is also ni p( )rtant to people. our behavior ss nice hatuteaf and tends to be mtlueneed by ininve tunenons such as thought, choice, and ue systems. The limbic system forms a fi inge along the er edge of the cerebrum, It is mi oh ed in learn and menior\ç motion, hunget, sex, and aggres o If a narticular Ixurt of the limbie cvstem is unaged. people can recall old memories but do ‘t create new memories. For example. a person h clamape to that area may have vivid childhood mnone of playing with his or her Nisler but may ne able to memember that this Name sister i isited 1er that das Researchers have also found that struction of mother specmfie area of the limbie tem can leacf animals to show passive behavior. ‘struetion of a different area ol the limhie system es sonic aniniais to behave ahgressivelv. even en there ecnis title reason to do so. . [he cerebrum tLatin for “brain”) is the crown ing glory of the brain, Only in human beings does the cerebrum make up such a large part of’ the brain. Ihe cerebrum accounts for about 70 percent of’ the weight of the brain. [he surface of the cere brum is wrinkled ii ith ridges and valleys. This sur face is the cerebral cortex. cCo,’tcx is the Latin word for “bark of’ a tree.’) The cerebral cortex is the outer layer of the brain, lust as bark is the outer layer of a tree. [he cerebral cortex is the Irt of the brain that we tend to think of when we talk about the brain. It is the jrt that makes us uniciuufv human, the part that thinks. In addition io thinking, the cerebral cortex is also concerned with memory language. emotions, complex motor functions. perception, and much more. The cerebral Cortex: What Makes Us Unique Phe cerebral cortex is composed of two sides—a left side and a right side. Each side is called a hemi sphere. (The Greek hemi- means “half.” Thus, each half of the brain is half a sphere, just as each half of planet Earth is a hemisphere. [‘o visuali:e the cere bral cortex, think of a nalnnt. [he shell of the wal iii it is like the skull. just as the walnut has tn o sides that are connected. so does the brain. In the brain, t lie structure that connects t lie two hemispheres is called the corpus callosurn. bntei’estmgly, information received by one side of the body is transmitted to the opposite hemi— sphere of the brain. Lor example, if you touch sonic’thing u ith your left hand, that information is sent to the right side of your brain. Conversely if you t mcli soniething ii nh \ our right hand, the left hemisphere om your brain receives the information. [lie corpus eallosu in aids in getting in formation from one side of the brain to the other. Each hemisphere of the cerebral cortex is dlii icIer! into four parts, or lobes. [he frontal lobe lies behind the foi’eheacI. and the parietal lobe lies to the top and rear of the hear!. I he temporal lobe lies to m lie side. tust below the ears. I he occipital lobe is at the back of the head. iSee Ligcire 3.n on page hl.) Sonic sensations, such as visual sensations, are received primarily in one lobe. Honever, each lobe dloes not necessarily ac,t independently from the others, Some functions require the interplay of sev eral lobes. [he involvement of the cerebral cortex in m lie Nenses and motor behavior is a good illustration this interaction. t3101.0CY AND BEHAVIOR 61 I Sensory and Motor Areas of the Brain Motor Area Sensory Area Legs I Toes • Trunk Knees • Head Ships C Shoulders Arms • Hands O Fingers O Face Wrists C Fingers QNeck C Eyes Qjaw o Ups O Tongue FIGURE 3.6 Certain areas of the cerebral cortex control specific sensory and motor functions. fhe occipital lobe contains the primary visual area of the cerebral cortex. When light strikes the eyes, neurons in the cipital lobe fire, enabling us to see. We also ‘see” [lashes of light if neurons in the occipital lobe are umulated b’ electricity Damage to different parts of the occipital lobe Lan create unusual conditions. People with damage to one area may be able to recognize an object, but hey may he unable to differentiate it from another object that is similar. For example. if shown a key they may know that what they see is a key but they may not be able to tell it apart from another key that looks different. People with damage to another area 62 CHAPTFR 3 may he able to report that they have seen a face, but they may not be able to identify that itis the face of a close friend, It is true that a person with brain damage may be able to report that he or she has seen a face but may not be able to identify that it was the face of REVI S TED a close friend. Damage to a particular area in the occipital lobe of the cerebral cortex can create this condition. TRUTH he hearmg, or auditory, area at the cortex lies temporal lobe. Smnds are relayed [ram the o the thalamus to the auditory area. \Vhen this ii s, we hear sounds, It a specific area of the ternii cortex is cLmagecl, a persofl may not he able cognize vers common sounds, such as a door iinging. \lessages received from the skin senses isee pter 4 are pi’Olected to the sensory cortex in the etal lobe. T’hee sensations include warmth and cold odic h, and pain. Di ffbrent neu rons fire, depending on whether you has e c ratched your nose, touched a hot sto\ e, or been stung by a bee. \Vhrn rodd stepped on \larc toe, the message was relayed from the toe lie parieial lobe of \larc brain, Ehe motor cortex mn he frontal lobe, However, s involved when \lare grabbed his loot and ted rubbing it. eurons in the motor cortex fire icn we mos e certHin parts at our body \Vhen we our hands or wiggle our toes, different parts of frontal lobe ate si imtilated. \\‘ei’nickc which is locatedl in the temnno ral lobe, pieces together sounds and sights. People svith damage to this area may find it diffIcult to undlerst and speech. I hey may he able to speak, hut their speech often m meaningless. Par example, when nked to describe a picture of two bays steal ing cookies beh m nd a iss (mans bat Is, one rLspondedl. ‘\lother is ann her working her work to get her better. but when shey looking the two boys looking the other part. hey working another time” Geschwind, 1979. Brocag jN located in the frontal lobe near the section at the motor cortex that controls the areas of the face used for speaking. When Brocas area is damaged. people speak slowly and laboriously icing simple sentences. Lomprehension is d{tiite .ooel. but they may speak only Ices’ svords. For example, a person with Broea aphasia who wants to say “the three bananas are lying on the table” may produce onlI “bananas lie table,” area, person area The same hemisphere that contains most language functions also is usually involved in logic, problem solv ing. and mathematical computation than is the other hemisphere i Borod. 1Q92 1 Hellige, 1990). The nanlanguage hemisphere is relatis’elv more concerned with the imagination, art, feelings, and spatial relations. In our society people often speak ol certain abil as belonging to the right brain or to the left brain. I htis, people ss ho ai’e very logical are said to be ‘left-brained.’ svliile people who are partictilarly reative are called “rteht-broinecl.’ This idea. hosv c’s er, has become greatly exaggerated. Although some differences do c.\ist, the hemispheres do not act independently of each other (Hellige. 19901. Lven t bough each hemisphere is capable of fune mionine by itself, the brain functions better nhen the two hemispheres svork together. One hemi here does play a special role in language. ss bile the other hemisphere plays a special role In feelings. I losvevcr. both hemispheres are ins’olvcd in logic, creativity and intuition. more \Itich of the cerebral cortex omposed of areas that are directly responsible ensory and motor functions. Other areas, called ‘ociation areas, serve mainly to shape informa into something meaningful on which we can For e\ample, some association areas piece “ther sensory information. Certain neurons in occipital lobe ‘ire when we vertical lines. crs fire when we ee hor:ontaf lines. .\ei ivitv in association areas then integrates the information iat we ee a meaningful form such as a tree, the und, a swiriC set, or a letter of the alphabet. Other ociation areas make possible such complex psv logical ti in lions as thought and language. o view Although the left and the hemispheres of the brain have main’ of the e functions, they differ mn a number of was s. For nrple. for nearly all right-handed people, lan lge lunctions are based m the left hemisphere. I guage In nc t i on are a I o basedl in the left hem i crc 1 about two out of three left-handed people. nlv in a very small percentage of people arc cuage I tmnct ions based in the right hemisphere. ‘A’ithin the hemisphere containing the language ‘cttons. two key language areas are Fracas area I \\brnicke area. Damage to either area is likely ause an aphasia, a dlifliculty with inderstandling or producing language. at ities - specific I’ I aspects TRUTH ‘d - ii V i S It is not true that some people are “le ft-brained” and others are “right-brained.” Both hemispheres of the brain are li’i involved in most human I I F 0 activities and abilities. IIt L 1 O(IY .\\D t3EHA\’IOR 63 A common belief is that people who are very logical (such as Judges) are “left-brained” whereas people who are \ Inc Ii o I iv hat vvc h( ) lopi 5K have learned about left- and right hemisphere functioning conies from people ii ho len e had split brain operations In a split-brat n operation. the corpus callosuni, which connects the mo hemispheres. is cut. fbis procedure. although performed only rareh3 is some times med to help people with serious neural cbsorders such as severe eases of epilepsy. People with epilepsy expenence sei:nrcs, which are bursts of abnormal neuron firings that generally occur in one hemisphere and then spread to the other. Lultnig the corpus eallosum can reduce the severity of the ei:rtre by pr’entiiig them from spreading. \fter die uracrv, patients usually function quite dice I vs lv dcpite their hemispheres inability to coni 111 Inmcate with cac hi othcr. I loive er, the urger\ does have some subtle ects on functmonmn. I or exaniple. people max ne Oid to describe crhallv the objects they hold in leir riht hand hut not what they hold in their LIt “and Kaz:aniga. I o I i h n is because if an object held a ‘he siphi hind, the nilorination is ent to tie let t I ieni nphere vhn h mi most neonle eon tins ianguage abi lt1es Hawet er, f the same object held m the tell hand, i hits inlormation is rjectccf the right lie in nphe re. wh dii has cry little ian Jijgc ability. Ii n important to cnicmher that for spl’ \t ii Ii in! act corpus cailosums. the hemi eneresin’,aI I it ‘ilc topet h r. In us, most people in des nbc ,ibiccis held in either hand. :‘ 64 Il.’Th LR 3 more creative (such as artists) are “right-brained.” This beliel, howeve,i has little scientific validity. Jethods of Studying the i?raan \luch A our earlier understanding of the brain caine 1mm studies of people with head inJuries. Foda\. researchers increase their l<nonleclge of the brain and its functions by using a variety of tech nid)uds to study damaged and intact brains. One way that recearchers have been able to see liotv the brain is related to psi chological I tmncti( ns is through t lie studh of accidents and brain damage. Brain damage from head injuries call result in loss of \ ision and heaimng. r onhusion, nr Ius of nieniorv In sonic cases, the l)s5 K laKe 0 t lie brain may result iii cia! ivelv little 0 unction. Yet the loss ul ital. niailer pails can result in language problems. nicniorv loss, or Peat Ii. In oilier words, which particular area is dam iged may have a greater elfect than the amount of lie damage. b icc i neal iniulauun uf i lie brain has hutvn that speemle’ o eas are associated wit Ii spcct lie R pes of w ncat i, ‘ns ucli as seeing light or iceling a tap un the arm) or motor activities (such as nalking). c lassie research by Jo Lielgaclo I hoP) used ‘cctrical stmniulation ol (lie brain to hotv how an annual could lie made to change behavioral ia! merns. fhe researchers implanted an elect rode into a p ANDOTHER STUDIES STOR IES TRUE Is Phineas Gage Still the Same Man? he ability of the brain to withstand some accidents is nothing less than remark able. In some instances, people have not only sur vived severe injuries to the brain, but they have continued to live fairly normal lives. Sometimes, though, the victim is not quite the same as before the accident. Consider the case of Phineas Gage. Young Mr. Gage was a promising railroad worker. His character was outstanding and SkUll he was well liked. But all that changed one day in 1 848. While he was tamping down the blasting powder for a dynamite charge, Gage accidentally set the pow der off, and an inch-thick metal rod shot upward through his brain and out the top of his head, The rod landed many yards away. Gage fell back in a heap. Yet he was not dead. His cowork ers watched in shock as he stood up a few moments later and spoke. They drove him by oxcart to a local doctor, John Harlow. As the doc tor marveled at the hole through Gage’s head, Gage asked when the doctor thought he’d be able to return to work. Everyone, including the doctor, was surprised that Phineas Gage even survived the accident. Two months later, the physical effects of Gage’s wounds had healed. He walked about, spoke nor mally enough, and was aware of his surroundings. However, Gage had changed. He no longer was a dependable worker. He had also become foul mouthed and ill-mannered. It had become clear that the accident had had some serious psycho logical consequences. Gage died 1 3 years later during an epileptic seizure. Dr. Harlow persuaded Gage’s family to donate his skull to the Warren Medical Museum at T IA 4 Harvard University. Generations of biologists and psychologists have studied the skull and won dered how Gage’s changes in personality might have been caused by damage to his brain. According to biologists Hanna and Antonio Damasio (1992), the way in which the rod had entered the brain had spared the parts of the frontal lobes that were involved in lan guage and motor behavior. Thus, Gage was able to speak normally and move about easily. However, the rod had severely damaged a part of the under side of the frontal lobes, causing the disturbance in personality. The Damasios note that people who suffer damage to the same part of the brain today experience similar changes in personality. These individuals are often unable to censor their thoughts before speaking. As a result, they may blurt out thoughts that they would have kept to themselves before their brains were injured. Other researchers also have found changes in patients’ personalities after brain injuries. In gen eral, damage to right frontal areas can produce impulsive and rule-breaking behaviors, such as interrupting conversations (KoIb & Taylor, 1981). People with frontal-lobe injuries are also less likely to make spontaneous facial expressions. The com bination of excessive talking and lack of facial expressions may make these individuals seem like different people than they were before. Think About II If a person suffers a major head injury in an acci dent and then acts differently afterward, can we assume that brain damage was responsible for the personality change? Why or why not? - ‘I I bully brain. \\ hen the brain was stimulated, the bull dramatically stopped his charge and circled to the right. In another classic tucln James Olds and Peter \lilner tOlds, 196) used rats who had electiocles implanted in their brains to learn about the tune ions ol the h\ pothalamus. \Vhen the rats pressed a lever the electrodes stimulated the portion of the hspothaiamus where they w re implanted. As it turned out, the rats found this stimulation pleasur able—so pleasurable that the rats would press the lever up to 100 times a minute lust to reehe the timulation. in some cases, hungry rats chose elec trical stimulation os er food, hhe part of the hs po thalamus where the electrodes were implanted thus became known as a ‘pleasure center.’ Electrical stimulation of the brain is not always reliable as a research tool, stimulation in the same place can produce different effects at dilierent times. (an one ocr aslon, a rat nay eat when a portion of the brain is stimulated but on another occasion it may drink. 1 he ateas that produce pleasant and unpleasant scitsations hi lx’ople ma\ also sam from rerson to p i on and from da\ to day (he electroen cephalogram i EEC) is a device that records the dcc i rn al acuvi c of ihe brain. Elect rocles atta hcd to the calp with tape or pacte detect small amounts of electrical actisity called brain wases. Researchers have learned that certain brain wave patterns are issociated with feelings of ‘claxatmon and with The photograph at left shows an image obtained by a CAT scan. By producing a three-dimensional view of the brain, a CAT scan can reveal hidden braIn damage. The 66 uFI’P (ER 3 deep. (See Chapter 5.) Researchers and physicians can use electroencephalogram readings to help diagnose some kinds of psychological disorders and to help locate tumors. in recent years, scientists have designed new techniques for examining the brain. Fhese techniques use computers to generate images of the brain from various sources of information (Coleman, 1995; Posner & Raichie. 1994). Images of the brain can provide information about brain damage and other abnormalities. Imaging tech niques can also he used for early diagnoses of can cers and other problems. In addition, physicians ran use imaging to aid them during dill ic nIt and intricate surgeries. In computerized axial tomography ((‘AT) scans, i mosing ring passes X-ray beams around and through the head. ihe density of the brain tissue determines how muc h radiation is absorbed. omputers measure the amounts of radiation and piece together a three-dimensional view of the brain that can be displayed on a ideo monitor. In magnetic resonance imaging \4R1), a person irs in a very powerful magnetic field, Radio waves then cause parts of the brain to give off extra energy 1 his energy is measured from multiple angles and is i m’anslaied by computer into a visual image of the brainy anatomy kIRI is more powerful than a CAT scan and can show details more clearly [‘or examile, MRI is more effective at revealing small injuries and abnormalities in hard-to-see areas. photograph on the right shows a person entering MRI apparatus. For people who fear enclosed spaces, the time spent lying in the MRI field can be uncomfortable. Pos itron emission tomography (PE T scans Jib Irom CAT scans and MRI becaus e they show the ivity of the brain rather than a snapshot of the un at a given time. scientists can see the brain I nally at work. The per son is injected wtth lioactive sugar. As the sugar reac hes the brain, re of it is used \\ here bra in activiI is greater. A unputer image is generated based on the activity e PET scan has been used by researchers to see ach parts of the brain are most active when we listening to music, workin g out a math problem. ng language, or plas np chess uol clmanRakie, P5; Raichle. I 9P4, The PET scan reveals which i_Is of the brain are activated u tide the event is uallv taking place Po, if you rais e your hand, the unputer u ill show act ivdv in one area. If von sud ily start to sing a song, another area will light up. Tsing these rese arch techniques, psychologists ye learner! that the mind i a un duet of the I nain. day it is generally agreed that for every mental nt, such as a thotieht or a feel ing, there are umpanving. rtnuierlvng biolog ical events. laging teLhniques have allowed us to explore we deeply how the nervous stem , particularly hrin, lunctuons u hlc e are 1 thtn n gk , feeling, J moving. The study of brain abn ormalities has o revealed that the brain has gre at flexibility In er words, when parts of the bra in have under ne damage. other areas of the brain can some nes take over the functions ot the damager! areas. NINKIN ABOUT PSYCHOLOGY I. \Vhv is the cerebral cortex imp ortant? 2. Describe two differences betw een the left hemisphere and the right hemisph ere of the cerebral cortex. 3. List three different imaging tech niques used to study the brain. 4. Critical Thinking Wh y do you think it benefits people to have brains that are ilexihie? What would happen if brains were riot flexible? 3 The Endocrine SysLem e endocrine system consists of glands that rete substances, called hormones, into the odstrearn. The word Iiou,nonc is derived from the A PET scan shows brain activity as it occurs. (reek Iiorniun. meaning io stunulae’ or ‘to Hormones stimulate growth and many kinds of reactions. ue h as change s in act ivuv levels and moods. Because hormones affect behavior and emotional reactions. pss cholog ists \vho study the biology of behavior are also interested in the endocrine system Like neurotransnutters hormo ne ha\ e specti;c receptor sites. Although the var ious hormones cir culate throughout the body, thes act on l\ on hor mone receptors ui Lertai n places. I lormones are prod riced by eve nil differen t glands. l’hcse glands include the rv gland, the thyroid gland, the adrenal glands, and he testes and the ovaries. u ce Lipure 3.7 on page Pb.) excite. e Pituitary Gland 7hc S itriltarv gland lies just below the hvpothala ‘s about the sire of a pm. but it is so impor tint (ha t has been referred to as the ‘maste gland.’ Ilic itrumary gland, whi ch is stimulate y the hvpothak us, is responsible for the s’ etion of many differ hormones that af fe various :lspeets of hehavioi, ro\th hormone, or example regulates the growth of muscles, ho s, anc glands hmldren hose growth patterns see ormallv slow often catch up to others the San e u lien doctors give them Cro\vth hormone, onie hormones feet fem a in relation to regnamc’ and in lering. Probe tin s iulates pro c[uction of mus. ‘ I ‘ rn in nursing women. ‘voemn is responsibl or timulating labor in p unant \voineil, onietunes sr hen a pi’egnant u oma is over ,an obstetrician may induce labo r by injee in e noman \\ith oxytocin. BlOT Y 1 O r A’xI) BEH\VIOR 67 H. 4