Please proceed to the next section.

2-10 What are the functions of the various cerebral cortex regions?

Older brain networks sustain basic life functions and enable memory, emotions, and basic drives. Newer neural networks within the cerebrum—the two cerebral hemispheres contributing 85 percent of the brain’s weight—form specialized work teams that enable our perceiving, thinking, and speaking. Like other structures above the brainstem (including the thalamus, hippocampus, and amygdala), the cerebral hemispheres come as a pair. Covering those hemispheres, like bark on a tree, is the cerebral cortex, a thin surface layer of interconnected neural cells. It is your brain’s thinking crown, your body’s ultimate control and information-processing center.

As we move up the ladder of animal life, the cerebral cortex expands, tight genetic controls relax, and the organism’s adaptability increases. Frogs and other small-cortex amphibians operate extensively on preprogrammed genetic instructions. The larger cortex of mammals offers increased capacities for learning and thinking, enabling them to be more adaptable. What makes us distinctively human mostly arises from the complex functions of our cerebral cortex.

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If you opened a human skull, exposing the brain, you would see a wrinkled organ, shaped somewhat like the meat of an oversized walnut. Without these wrinkles, a flattened cerebral cortex would require triple the area—roughly that of a large pizza. The brain’s left and right hemispheres are filled mainly with axons connecting the cortex to the brain’s other regions. The cerebral cortex—that thin surface layer—contains some 20 to 23 billion of the brain’s nerve cells and 300 trillion synaptic connections (de Courten-Myers, 2005). Being human takes a lot of nerve.

Each hemisphere’s cortex is subdivided into four lobes, separated by prominent fissures, or folds (FIGURE 2.23). Starting at the front of your brain and moving over the top, there are the frontal lobes (behind your forehead), the parietal lobes (at the top and to the rear), and the occipital lobes (at the back of your head). Reversing direction and moving forward, just above your ears, you find the temporal lobes. Each of the four lobes carries out many functions, and many functions require the interplay of several lobes.

More than a century ago, surgeons found damaged cortical areas during autopsies of people who had been partially paralyzed or speechless. This rather crude evidence did not prove that specific parts of the cortex control complex functions like movement or speech. After all, if the entire cortex controlled speech and movement, damage to almost any area might produce the same effect. A TV with its power cord cut would go dead, but we would be fooling ourselves if we thought we had “localized” the picture in the cord.

Motor Functions Scientists had better luck in localizing simpler brain functions. For example, in 1870, German physicians Gustav Fritsch and Eduard Hitzig made an important discovery: Mild electrical stimulation to parts of an animal’s cortex made parts of its body move. The effects were selective: Stimulation caused movement only when applied to an arch-shaped region at the back of the frontal lobe, running roughly ear-to-ear across the top of the brain. Moreover, stimulating parts of this region in the left or right hemisphere caused movements of specific body parts on the opposite side of the body. Fritsch and Hitzig had discovered what is now called the motor cortex.

MAPPING THE MOTOR CORTEX Lucky for brain surgeons and their patients, the brain has no sensory receptors. Knowing this, Otfrid Foerster and Wilder Penfield were able to map the motor cortex in hundreds of wide-awake patients by stimulating different cortical areas and observing responses. They discovered that body areas requiring precise control, such as the fingers and mouth, occupy the greatest amount of cortical space (FIGURE 2.24). In one of his many demonstrations of motor behavior mechanics, Spanish neuroscientist José Delgado stimulated a spot on a patient’s left motor cortex, triggering the right hand to make a fist. Asked to keep the fingers open during the next stimulation, the patient, whose fingers closed despite his best efforts, remarked, “I guess, Doctor, that your electricity is stronger than my will” (Delgado, 1969, p. 114).

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More recently, scientists were able to predict a monkey’s arm motion a tenth of a second before it moved—by repeatedly measuring motor cortex activity preceding specific arm movements (Gibbs, 1996). Such findings have opened the door to research on brain-controlled computers.

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BRAIN–COMPUTER INTERFACES By eavesdropping on the brain, could we enable a paralyzed person to move a robotic limb? Could a brain–computer interface command a cursor to write an e-mail or do an online search? To find out, Brown University brain researchers implanted 100 tiny recording electrodes in the motor cortexes of three monkeys (Nicolelis, 2011; Serruya et al., 2002). As the monkeys gained rewards by using a joystick to follow a moving red target, the researchers matched the brain signals with the arm movements. Then they programmed a computer to monitor the signals and operate the joystick. When a monkey merely thought about a move, the mind-reading computer moved the cursor with nearly the same proficiency as had the reward-seeking monkey. In follow-up experiments, both monkeys and humans have learned to control a robot arm that could grasp and deliver food (Collinger et al., 2013; Hochberg et al., 2012; Velliste et al., 2008; see FIGURE 2.25).

Research has also recorded messages not from the arm-controlling motor neurons, but from a brain area involved in planning and intention (Leuthardt et al., 2009; Musallam et al., 2004). In one study, a monkey seeking a juice reward awaited a cue telling it to reach toward a spot flashed on a screen in one of up to eight locations. A computer program captured the monkey’s thinking by recording the associated activity. By matching this neural activity to the monkey’s subsequent pointing, the mind-reading researchers could program a cursor to move in response to the monkey’s thoughts. Monkey think, computer do.

If this technique works, why not use it to capture the words a person can think but cannot say (for example, after a stroke)? Cal Tech neuroscientist Richard Andersen (2004, 2005) has speculated that researchers could implant electrodes in speech areas, then “ask a patient to think of different words and observe how the cells fire in different ways. So you build up your database, and then when the patient thinks of the word, you compare the signals with your database, and you can predict the words they’re thinking. Then you take this output and connect it to a speech synthesizer. This would be identical to what we’re doing for motor control.” With this goal in mind, the U.S. Army is investing $6.3 million in neuroscientists’ efforts to build a helmet that might read and transmit soldiers’ thoughts (Piore, 2011).

Clinical trials of such cognitive neural prosthetics are now under way with people who have suffered paralysis or amputation (Andersen et al., 2010; Nurmikko et al., 2010). The first patient, a paralyzed 25-year-old man, was able to mentally control a TV, draw shapes on a computer screen, and play video games—all thanks to an aspirin-sized chip with 100 microelectrodes recording activity in his motor cortex (Hochberg et al., 2006). If everything psychological is also biological—if, for example, every thought is also a neural event—then perhaps microelectrodes could detect thoughts well enough to enable people to control their environment with ever-greater precision (see FIGURE 2.26).

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Sensory Functions If the motor cortex sends messages out to the body, where does the cortex receive incoming messages? Penfield identified a cortical area—at the front of the parietal lobes, parallel to and just behind the motor cortex—that specializes in receiving information from the skin senses and from the movement of body parts. We now call this area the somatosensory cortex (Figure 2.24). Stimulate a point on the top of this band of tissue and a person may report being touched on the shoulder; stimulate some point on the side and the person may feel something on the face.

The more sensitive the body region, the larger the somatosensory cortex area devoted to it (Figure 2.24). Your supersensitive lips project to a larger brain area than do your toes, which is one reason we kiss with our lips rather than touch toes. Rats have a large area of the brain devoted to their whisker sensations, and owls to their hearing sensations.

Scientists have identified additional areas where the cortex receives input from senses other than touch. Any visual information you are receiving now is going to the visual cortex in your occipital lobes, at the back of your brain (FIGURE 2.27 and FIGURE 2.28). Stimulated in the occipital lobes, you might see flashes of light or dashes of color. (In a sense, we do have eyes in the back of our head!) Having lost much of his right occipital lobe to a tumor removal, a friend was blind to the left half of his field of vision. Visual information travels from the occipital lobes to other areas that specialize in tasks such as identifying words, detecting emotions, and recognizing faces.

Any sound you now hear is processed by your auditory cortex in your temporal lobes (just above your ears; see Figure 2.28). Most of this auditory information travels a circuitous route from one ear to the auditory receiving area above your opposite ear. If stimulated in your auditory cortex, you might hear a sound. MRI scans of people with schizophrenia have revealed active auditory areas in the temporal lobes during the false sensory experience of auditory hallucinations (Lennox et al., 1999). Even the phantom ringing sound experienced by people with hearing loss is—if heard in one ear—associated with activity in the temporal lobe on the brain’s opposite side (Muhlnickel, 1998).

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Association Areas So far, we have pointed out small cortical areas that either receive sensory input or direct muscular output. Together, these occupy about one-fourth of the human brain’s thin, wrinkled cover. What, then, goes on in the remaining vast regions of the cortex? In these association areas (the peach-colored areas in FIGURE 2.29), neurons are busy with higher mental functions—many of the tasks that make us human.

Electrically probing an association area won’t trigger any observable response. So, unlike the somatosensory and motor areas, association area functions cannot be neatly mapped. Their silence has led to what Donald McBurney (1996, p. 44) called “one of the hardiest weeds in the garden of psychology”: the claim that we ordinarily use only 10 percent of our brain. (If true, wouldn’t this imply a 90 percent chance that a bullet to your brain would strike an unused area?) Surgically lesioned animals and brain-damaged humans bear witness that association areas are not dormant. Rather, these areas interpret, integrate, and act on sensory information and link it with stored memories—a very important part of thinking. Simple tasks often increase activity in small brain patches, far less than 10 percent. Yet complex tasks integrate many islands of brain activity: some of which take in information and perform automatic tasks; others of which require conscious control (Chein & Schneider, 2012). The brain is an integrated system, with no dead spot for a stray bullet.

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Association areas are found in all four lobes. The prefrontal cortex in the forward part of the frontal lobes enables judgment, planning, and processing of new memories. People with damaged frontal lobes may have intact memories, high scores on intelligence tests, and great cake-baking skills. Yet they would not be able to plan ahead to begin baking a cake for a birthday party (Huey et al., 2006).

Frontal lobe damage also can alter personality and remove a person’s inhibitions. Consider the classic case of railroad worker Phineas Gage. One afternoon in 1848, Gage, then 25 years old, was using a tamping iron to pack gunpowder into a rock. A spark ignited the gunpowder, shooting the rod up through his left cheek and out the top of his skull, leaving his frontal lobes damaged (FIGURE 2.30). The rod not only damaged some of Gage’s left frontal lobe’s neurons, but also about 11 percent of its axons that connect the frontal lobes with the rest of the brain (Van Horn et al., 2012). To everyone’s amazement, he was immediately able to sit up and speak, and after the wound healed he returned to work. But having lost some of the neural tracts that enabled his frontal lobes to control his emotions, the affable, soft-spoken man was now irritable, profane, and dishonest. This person, said his friends, was “no longer Gage.” His mental abilities and memories were intact, but his personality was not. (Although Gage lost his railroad job, he did, over time, adapt to his injury and find work as a stagecoach driver [Macmillan & Lena, 2010].)

Studies of others with damaged frontal lobes have revealed similar impairments. Not only may they become less inhibited (without the frontal lobe brakes on their impulses), but their moral judgments may seem unrestrained by normal emotions. Would you advocate pushing one person in front of a runaway trolley to save five others? Most people do not, but those with damage to a brain area behind the eyes often do (Koenigs et al., 2007). With their frontal lobes ruptured, people’s moral compass seems to disconnect from their behavior.

Association areas also perform other mental functions. The parietal lobes, parts of which were large and unusually shaped in Einstein’s normal-weight brain, enable mathematical and spatial reasoning (Witelson et al., 1999). Stimulation of one parietal lobe area in brain-surgery patients produced a feeling of wanting to move an upper limb, the lips, or the tongue without any actual movement. With increased stimulation, patients falsely believed they had moved. Curiously, when surgeons stimulated a different association area near the motor cortex in the frontal lobes, the patients did move but had no awareness of doing so (Desmurget et al., 2009). These head-scratching findings suggest that our perception of moving flows not from the movement itself, but rather from our intention and the results we expected.

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On the underside of the right temporal lobe, another association area enables us to recognize faces. If a stroke or head injury destroyed this area of your brain, you would still be able to describe facial features and to recognize someone’s gender and approximate age, yet be strangely unable to identify the person as, say, your grandmother.

Nevertheless, to reemphasize, we should be wary of using pictures of brain “hot spots” to create a new phrenology that locates complex functions in precise brain areas (Beck, 2010; Shimamura, 2010; Uttal, 2001). Complex mental functions don’t reside in any one place. There is no one spot in a rat’s small association cortex that, when damaged, will obliterate its ability to learn or remember a maze. Your memory, language, and attention result from the synchronized activity among distinct brain areas and neural networks (Knight, 2007). Ditto for religious experience. More than 40 distinct brain regions become active in different religious states, such as prayer and meditation, indicating that there is no simple “God spot” (Fingelkurts & Fingelkurts, 2009). The point to remember: Our mental experiences arise from coordinated brain activity.

2-11 To what extent can a damaged brain reorganize itself, and what is neurogenesis?

Our brains are sculpted not only by our genes but also by our experiences. MRI scans show that well-practiced pianists have a larger-than-usual auditory cortex area that encodes piano sounds (Bavelier et al., 2000; Pantev et al., 1998). In Chapter 4, we’ll focus more on how experience molds the brain. For now, let’s turn to another aspect of the brain’s plasticity: its ability to modify itself after damage.

Some brain-damage effects can be traced to two hard facts: (1) Severed brain and spinal cord neurons, unlike cut skin, usually do not regenerate. (If your spinal cord were severed, you would probably be permanently paralyzed.) And (2) some brain functions seem preassigned to specific areas. One newborn who suffered damage to temporal lobe facial recognition areas later remained unable to recognize faces (Farah et al., 2000). But there is good news: Some neural tissue can reorganize in response to damage. Under the surface of our awareness, the brain is constantly changing, building new pathways as it adjusts to little mishaps and new experiences.

Plasticity may also occur after serious damage, especially in young children (Kolb, 1989; see also FIGURE 2.31). Constraint-induced therapy aims to rewire brains and improve the dexterity of a brain-damaged child or even an adult stroke victim (Taub, 2004). By restraining a fully functioning limb, therapists force patients to use the “bad” hand or leg, gradually reprogramming the brain. One stroke victim, a surgeon in his fifties, was put to work cleaning tables, with his good arm and hand restrained. Slowly, the bad arm recovered its skills. As damaged-brain functions migrated to other brain regions, he gradually learned to write again and even to play tennis (Doidge, 2007).

The brain’s plasticity is good news for those blind or deaf. Blindness or deafness makes their unused brain areas available for other uses (Amedi et al., 2005). If a blind person uses one finger to read Braille, the brain area dedicated to that finger expands as the sense of touch invades the visual cortex that normally helps people see (Barinaga, 1992a; Sadato et al., 1996). Plasticity also helps explain why some studies have found that deaf people have enhanced peripheral and motion-detection vision (Bosworth & Dobkins, 1999; Shiell et al., 2014). In deaf people whose native language is sign, the temporal lobe area normally dedicated to hearing waits in vain for stimulation. Finally, it looks for other signals to process, such as those from the visual system.

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Similar reassignment may occur when disease or damage frees up other brain areas normally dedicated to specific functions. If a slow-growing left hemisphere tumor disrupts language (which resides mostly in the left hemisphere), the right hemisphere may compensate (Thiel et al., 2006). If a finger is amputated, the somatosensory cortex that received its input will begin to receive input from the adjacent fingers, which then become more sensitive (Fox, 1984). So what do you suppose was the sexual intercourse experience of one patient whose lower leg had been amputated? “I actually experience my orgasm in my [phantom] foot. [Note that in Figure 2.24, the toes region is adjacent to the genitals.] And there it’s much bigger than it used to be because it’s no longer just confined to my genitals” (Ramachandran & Blakeslee, 1998, p. 36).

Although the brain often attempts self-repair by reorganizing existing tissue, it sometimes attempts to mend itself by producing new brain cells. This process, known as neurogenesis, has been found in adult mice, birds, monkeys, and humans (Jessberger et al., 2008). These baby neurons originate deep in the brain and may then migrate elsewhere and form connections with neighboring neurons (Aimone et al., 2010; Gould, 2007).

Cold War nuclear tests between 1945 and 1963 oddly later enabled scientists to confirm the birth of new brain neurons. The blasts released radioactive carbon isotopes, which carbon-dated neurons in the hippocampus, a brain center crucial to memory formation. By detecting neurons birthed since then, researchers discovered that 700 new hippocampus neurons are born daily, making nearly a 2 percent annual turnover rate (Kempermann, 2013; Spalding, 2013). Our bombs have taught us something about our brains.

Master stem cells that can develop into any type of brain cell have also been discovered in the human embryo. If mass-produced in a lab and injected into a damaged brain, might neural stem cells turn themselves into replacements for lost brain cells? Might surgeons someday be able to rebuild damaged brains, much as we reseed damaged lawns? Stay tuned. Today’s biotech companies are hard at work on such possibilities. In the meantime, we can all benefit from natural promoters of neurogenesis, such as exercise, sleep, and nonstressful but stimulating environments (Iso et al., 2007; Pereira et al., 2007; Stranahan et al., 2006).

2-12 What do split brains reveal about the functions of our two brain hemispheres?

Our brain’s look-alike left and right hemispheres serve differing functions. This lateralization is apparent after brain damage. Research spanning more than a century has shown that left hemisphere accidents, strokes, and tumors can impair reading, writing, speaking, arithmetic reasoning, and understanding. Similar right hemisphere damage has effects that are less visibly dramatic. Does this mean that the right hemisphere is just along for the ride? Many believed this was the case until the 1960s, when a fascinating chapter in psychology’s history began to unfold: Researchers found that the “minor” right hemisphere was not so limited after all.

In 1961, Los Angeles neurosurgeons Philip Vogel and Joseph Bogen speculated that major epileptic seizures were caused by an amplification of abnormal brain activity bouncing back and forth between the two cerebral hemispheres, which work together as a whole system. If so, they wondered, could they put an end to this biological tennis match by severing the corpus callosum, the wide band of axon fibers connecting the two hemispheres and carrying messages between them (see FIGURE 2.32)? Vogel and Bogen knew that psychologists Roger Sperry, Ronald Myers, and Michael Gazzaniga had divided cats’ and monkeys’ brains in this manner, with no serious ill effects.

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So the surgeons operated. The result? The seizures all but disappeared. The patients with these split brains were surprisingly normal, their personality and intellect hardly affected. Waking from surgery, one even joked that he had a “splitting headache” (Gazzaniga, 1967). By sharing their experiences, these patients have greatly expanded our understanding of interactions between the intact brain’s two hemispheres.

To appreciate these findings, we need to focus for a minute on the peculiar nature of our visual wiring, illustrated in FIGURE 2.33. Note that each eye receives sensory information from the entire visual field. But in each eye, information from the left half of your field of vision goes to your right hemisphere, and information from the right half of your visual field goes to your left hemisphere, which usually controls speech. Data received by either hemisphere are quickly transmitted to the other across the corpus callosum. In a person with a severed corpus callosum, this information-sharing does not take place.

Knowing these facts, Sperry and Gazzaniga could send information to a patient’s left or right hemisphere. As the person stared at a spot, they flashed a stimulus to its right or left. They could do this with you, too, but in your intact brain, the hemisphere receiving the information would instantly pass the news to the other side. Because the split-brain surgery had cut the communication lines between the hemispheres, the researchers could, with these patients, quiz each hemisphere separately.

In an early experiment, Gazzaniga (1967) asked these people to stare at a dot as he flashed HE•ART on a screen (FIGURE 2.34 below). Thus, HE appeared in their left visual field (which transmits to the right hemisphere) and ART in the right field (which transmits to the left hemisphere). When he then asked them to say what they had seen, the patients reported that they had seen ART. But when asked to point to the word they had seen, they were startled when their left hand (controlled by the right hemisphere) pointed to HE. Given an opportunity to express itself, each hemisphere indicated what it had seen. The right hemisphere (controlling the left hand) intuitively knew what it could not verbally report.

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When a picture of a spoon was flashed to their right hemisphere, the patients could not say what they had viewed. But when asked to identify what they had viewed by feeling an assortment of hidden objects with their left hand, they readily selected the spoon. If the experimenter said, “Correct!” the patient might reply, “What? Correct? How could I possibly pick out the correct object when I don’t know what I saw?” It is, of course, the left hemisphere doing the talking here, bewildered by what the nonverbal right hemisphere knows.

A few people who have had split-brain surgery have been for a time bothered by the unruly independence of their left hand, which might unbutton a shirt while the right hand buttoned it, or put grocery store items back on the shelf after the right hand put them in the cart. It was as if each hemisphere was thinking “I’ve half a mind to wear my green (blue) shirt today.” Indeed, said Sperry (1964), split-brain surgery leaves people “with two separate minds.” With a split brain, both hemispheres can comprehend and follow an instruction to copy—simultaneously—different figures with the left and right hands (Franz et al., 2000; see also FIGURE 2.35). (Reading these reports, I [DM] fantasize a patient enjoying a solitary game of “rock, paper, scissors”—left versus right hand.)

When the “two minds” are at odds, the left hemisphere does mental gymnastics to rationalize reactions it does not understand. If a patient follows an order (“Walk”) sent to the right hemisphere, a strange thing happens. The unaware left hemisphere doesn’t know why the patient begins walking. If asked, the patient doesn’t reply, “I don’t know.” Instead, the left hemisphere improvises—“I’m going into the house to get a Coke.” Gazzaniga (1988), who considers these patients “the most fascinating people on earth,” concluded that the conscious left hemisphere is an “interpreter” that instantly constructs explanations. The brain, he concludes, often runs on autopilot; it acts first and then explains itself.

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So, what about the 99.99+ percent of us with undivided brains? Does each of our hemispheres also perform distinct functions? Several different types of studies indicate they do. When a person performs a perceptual task, for example, brain waves, bloodflow, and glucose consumption reveal increased activity in the right hemisphere. When the person speaks or calculates, activity usually increases in the left hemisphere.

A dramatic demonstration of hemispheric specialization happens before some types of brain surgery. To locate the patient’s language centers, the surgeon injects a sedative into the neck artery feeding blood to the left hemisphere, which usually controls speech. Before the injection, the patient is lying down, arms in the air, chatting with the doctor. Can you predict what probably happens when the drug puts the left hemisphere to sleep? Within seconds, the person’s right arm falls limp. If the left hemisphere is controlling language, the patient will be speechless until the drug wears off. If the drug is injected into the artery to the right hemisphere, the left arm will fall limp, but the person will still be able to speak.

To the brain, language is language, whether spoken or signed. Just as hearing people usually use the left hemisphere to process spoken language, deaf people use the left hemisphere to process sign language (Corina et al., 1992; Hickok et al., 2001). Thus, a left hemisphere stroke disrupts a deaf person’s signing, much as it would disrupt a hearing person’s speaking (Corina, 1998).

Although the left hemisphere is adept at making quick, literal interpretations of language, the right hemisphere

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Simply looking at the two hemispheres, so alike to the naked eye, who would suppose they contribute uniquely to the harmony of the whole? Yet a variety of observations—of people with split brains, of people with normal brains, and even of other species’ brains—converge beautifully, leaving little doubt that we have unified brains with specialized parts (Hopkins & Cantalupo 2008; MacNeilage et al., 2009; and see Thinking Critically About: Handedness).

***

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In this chapter we have glimpsed an overriding principle: Everything psychological is simultaneously biological. We have focused on how our thoughts, feelings, and actions arise from our specialized yet integrated brain. In chapters to come, we will further explore the significance of the biological revolution in psychology.

From nineteenth-century phrenology to today’s neuroscience, we have come a long way. Yet what is unknown still dwarfs what is known. We can describe the brain. We can learn the functions of its parts. We can study how the parts communicate. But how do we get mind out of meat? How does the electrochemical whir in a hunk of tissue the size of a head of lettuce give rise to elation, a creative idea, or that memory of Grandmother?

Much as gas and air can give rise to something different—fire—so also, believed Roger Sperry, does the complex human brain give rise to something different: consciousness. The mind, he argued, emerges from the brain’s dance of ions, yet is not reducible to it. As neuroscientist Donald MacKay (1978) observed, “[My brain activity] reflects what I am thinking, as [computer] activity reflects the equation it is solving.” The mind and brain activities are yoked (no brain, no mind), he noted, but are complementary and conceptually distinct.

Cells cannot be fully explained by the actions of atoms, nor minds by the activity of cells. Psychology is rooted in biology, which is rooted in chemistry, which is rooted in physics. Yet psychology is more than applied physics. As Jerome Kagan (1998) reminded us, the meaning of the Gettysburg Address is not reducible to neural activity. Sexual love is more than blood flooding to the genitals. Morality and responsibility become possible when we understand the mind as a “holistic system,” said Sperry (1992) (FIGURE 2.36). We are not mere jabbering robots. Brains make thoughts. And thoughts change brains.

The mind seeking to understand the brain—that is indeed among the ultimate scientific challenges. And so it will always be. To paraphrase cosmologist John Barrow, a brain simple enough to be understood is too simple to produce a mind able to understand it.

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LEARNING OBJECTIVES

RETRIEVAL PRACTICE Take a moment to answer each of these Learning Objective Questions (repeated here from within this section). Then click the 'show answer' button to check your answers. Research suggests that trying to answer these questions on your own will improve your long-term retention (McDaniel et al., 2009).

2-10What are the functions of the various cerebral cortex regions?

2-11To what extent can a damaged brain reorganize itself, and what is neurogenesis?

2-12What do split brains reveal about the functions of our two brain hemispheres?

2-13What does research tell us about being left-handed? Is it advantageous to be right-handed?

TERMS AND CONCEPTS TO REMEMBER

RETRIEVAL PRACTICE Match each of the terms on the left with its definition on the right. Click on the term first and then click on the matching definition. As you match them correctly they will move to the bottom of the activity.

Test yourself repeatedly throughout your studies. This will not only help you figure out what you know and don’t know; the testing itself will help you learn and remember the information more effectively thanks to the testing effect.

Neural and Hormonal Systems

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Tools of Discovery and Older Brain Structures

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The Cerebral Cortex and Our Divided Brain

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