Discussion

Anatomy and Research MethodsChapter 3New methods allow researchers to examine living brains. (Dorsal view of brain)Trying to learn neuroanatomy (the anatomy of the nervous system) from a book is like trying to learn geography from a road map. A map can tell you that Mystic, Georgia, is about 40 km north of Enigma, Georgia. Similarly, a book can tell you that the habenula is about 4.6 mm from the interpeduncular nucleus in a rat’s brain (proportionately farther in a human brain). But these little gems of information will seem both mysterious and enigmatic unless you are interested in that part of Georgia or that area of the brain.This chapter does not provide a detailed road map of the nervous system. It is more like a world globe, describing the large, basic structures, analogous to the continents, and some distinctive features of each.The first module introduces key neuroanatomical terms and outlines overall structures of the nervous system. In the second module, we concentrate on the cerebral cortex, the largest part of the mammalian central nervous system. The third module deals with the main methods that researchers use to discover the functions of brain areas.Be prepared: This chapter contains a huge number of new terms. You should not expect to memorize all of them at once, and you should review this chapter repeatedly.Chapter OutlineModule 3.1Structure of the Vertebrate Nervous SystemTerminology to Describe the Nervous SystemThe Spinal CordThe Autonomic Nervous SystemThe HindbrainThe MidbrainThe ForebrainThe VentriclesIn Closing: Learning NeuroanatomyModule 3.2The Cerebral CortexOrganization of the Cerebral CortexThe Occipital LobeThe Parietal LobeThe Temporal LobeThe Frontal LobeHow Do the Parts Work Together?In Closing: Functions of the Cerebral CortexModule 3.3Research MethodsEffects of Brain DamageEffects of Brain StimulationRecording Brain ActivityCorrelating Brain Anatomy with BehaviorIn Closing: Research Methods and ProgressLearning ObjectivesAfter studying this chapter, you should be able to:1. Define the terms used to describe brain anatomy.2. Describe the principal functions of certain brain areas.3. List the four lobes of the cerebral cortex and name their principal functions.4. Describe the binding problem and explain its theoretical importance.5. Cite examples of several methods for studying the relationship between brain activity and behavior.Module 3.1Structure of the Vertebrate Nervous SystemYour nervous system includes a huge number of neurons, and an even huger number of synapses. How do all the parts work together to make one behaving unit? Does each neuron have a unique function? Or does the brain operate as an undifferentiated whole?The answer is something between those extremes. Consider an analogy to human society: Each individual has a specialty, such as teacher, farmer, or nurse, but no one performs any function without the cooperation of many other people. Similarly, brain areas and neurons have specialized functions, but they perform those roles by means of connections with other areas.Terminology to Describe the Nervous SystemFor vertebrates, we distinguish the central nervous system from the peripheral nervous system (see Figure 3.1). The central nervous system (CNS) is the brain and the spinal cord. The peripheral nervous system (PNS) connects the brain and spinal cord to the rest of the body. Part of the PNS is the somatic nervous system, which consists of the axons conveying messages from the sense organs to the CNS and from the CNS to the muscles. Another part of the PNS, the autonomic nervous system, controls the heart, intestines, and other organs. The autonomic nervous system has some of its cell bodies within the brain or spinal cord and some in clusters along the sides of the spinal cord.Figure 3.1   The human nervous systemThe central nervous system consists of the brain and spinal cord. The peripheral nervous system is the nerves outside the brain and spinal cord.Figure 3.2   Terms for anatomical directions in the nervous systemIn four-legged animals, the dorsal and ventral axes for the head are parallel to those for the rest of the body. However, humans’ upright posture has tilted the head, so the dorsal and ventral directions of the head are at right angles to those of the spinal cord.To follow a map, you must understand north, south, east, and west. Because the nervous system is three-dimensional, we need more terms to describe it. As Figure 3.2 and Table 3.1 indicate, dorsal means toward the back and ventral means toward the stomach. (A ventriloquist is literally a “stomach talker.”) In a four-legged animal, the top of the brain is dorsal (on the same side as the animal’s back), and the bottom of the brain is ventral (on the stomach side). The same would be true for you if you crawled on your hands and knees. However, when humans evolved upright posture, the position of the head changed relative to the spinal cord. For convenience, we still apply the terms dorsal and ventral to the same parts of the human brain as other vertebrate brains. Consequently, the dorsal–ventral axis of the human brain is at a right angle to the dorsal–ventral axis of the spinal cord. Figure 3.2 also illustrates the three ways of taking a plane through the brain, known as horizontal, sagittal, and coronal (or frontal).Table 3.2 introduces additional terms that are worth learning. Tables 3.1 and 3.2 require careful study and review. After you think you have mastered the terms, check yourself with the following “Stop & Check” questions.Table 3.1 Anatomical Terms Referring to DirectionsTermDefinitionDorsalToward the back, away from the ventral (stomach) side. The top of the human brain is considered dorsal because it has that position in four-legged animals.VentralToward the stomach, away from the dorsal (back) sideAnteriorToward the front endPosteriorToward the rear endSuperiorAbove another partInferiorBelow another partLateralToward the side, away from the midlineMedialToward the midline, away from the sideProximalLocated close (approximate) to the point of origin or attachmentDistalLocated more distant from the point of origin or attachmentIpsilateralOn the same side of the body (e.g., two parts on the left or two on the right)ContralateralOn the opposite side of the body (one on the left and one on the right)Coronal plane (or frontal plane)A plane that shows brain structures as seen from the frontSagittal planeA plane that shows brain structures as seen from the sideHorizontal plane (or transverse plane)A plane that shows brain structures as seen from aboveSTOP & CHECK1. What does ventral mean, and what is its opposite?2. What term means toward the midline, and what is its opposite?3. If two structures are both on the left side of the body, they are _____ to each other. If one is on the left and the other is on the right, they are _____ to each other.4. The bulges in the cerebral cortex are called _____ The grooves between them are called _____ANSWERS1. Ventral means toward the stomach side. Its opposite is dorsal. 2. medial; lateral 3. ipsilateral; contralateral 4. gyri; sulci. To remember sulcus, think of the word sulk, meaning “to pout” (and therefore lie low).The Spinal CordThe spinal cord is the part of the CNS within the spinal column. The spinal cord communicates with all the sense organs and muscles except those of the head. It is a segmented structure, and each segment has on both the left and right sides a sensory nerve and a motor nerve, as Figure 3.3 shows. One of the earliest discoveries about the functions of the nervous system was that the entering dorsal roots (axon bundles) carry sensory information, and the exiting ventral roots carry motor information. The cell bodies of the sensory neurons are in clusters of neurons outside the spinal cord, called the dorsal root ganglia. (Ganglia is the plural of ganglion, a cluster of neurons. In most cases, a neuron cluster outside the CNS is called a ganglion, and a cluster inside the CNS is called a nucleus.) Cell bodies of the motor neurons are inside the spinal cord.Table 3.2 Terms Referring to Parts of the Nervous SystemTermDefinitionLaminaA row or layer of cell bodies separated from other cell bodies by a layer of axons and dendritesColumnA set of cells perpendicular to the surface of the cortex, with similar propertiesTractA set of axons within the CNS, also known as a projection. If axons extend from cell bodies in structure A to synapses onto B, we say that the fibers “project” from A onto B.NerveA set of axons in the periphery, either from the CNS to a muscle or gland or from a sensory organ to the CNSNucleusA cluster of neuron cell bodies within the CNSGanglionA cluster of neuron cell bodies, usually outside the CNS (as in the sympathetic nervous system)Gyrus (pl.: gyri)A protuberance on the surface of the brainSulcus (pl.: sulci)A fold or groove that separates one gyrus from anotherFissureA long, deep sulcusIn the cross section through the spinal cord shown in Figures 3.4 and 3.5, the H-shaped gray matter in the center of the cord is densely packed with cell bodies and dendrites. Many neurons from the gray matter of the spinal cord send axons to the brain or to other parts of the spinal cord through the white matter, containing myelinated axons.Figure 3.3   Diagram of a cross section through the spinal cordThe dorsal root on each side conveys sensory information to the spinal cord; the ventral root conveys motor commands to the muscles.Figure 3.4   Photo of a cross section through the spinal cordThe H-shaped structure in the center is gray matter, composed largely of cell bodies. The surrounding white matter consists of axons.Each segment of the spinal cord sends sensory information to the brain and receives motor commands from the brain. All that information passes through tracts of axons in the spinal cord. If the spinal cord is cut at a given segment, the brain loses sensation from that segment and below. The brain also loses motor control over all parts of the body served by that segment and the lower ones.The Autonomic Nervous SystemThe autonomic nervous system consists of neurons that receive information from and send commands to the heart, intestines, and other organs. Its two parts are the sympathetic and parasympathetic nervous systems (see Figure 3.6). The sympathetic nervous system, a network of nerves that prepare the organs for a burst of vigorous activity, consists of chains of ganglia just to the left and right of the spinal cord’s central regions (the thoracic and lumbar areas). These ganglia have connections back and forth with the spinal cord. Sympathetic axons prepare the organs for “fight or flight,” such as by increasing breathing and heart rate and decreasing digestive activity. Because the sympathetic ganglia are closely linked, they often act as a single system “in sympathy” with one another, although certain events activate some parts more than others. The sweat glands, the adrenal glands, the muscles that constrict blood vessels, and the muscles that erect the hairs of the skin have sympathetic input but no parasympathetic input.Figure 3.5   A section of gray matter of the spinal cord (left) and white matter surrounding itCell bodies and dendrites reside entirely in the gray matter. Axons travel from one area of gray matter to another in the white matter.The parasympathetic nervous system, sometimes called the “rest and digest” system, facilitates vegetative, non-emergency responses. The term para means “beside” or “related to,” and parasympathetic activities are related to, and generally the opposite of, sympathetic activities. For example, the sympathetic nervous system increases heart rate, and the parasympathetic nervous system decreases it. The parasympathetic nervous system increases digestive activity, whereas the sympathetic nervous system decreases it. The parasympathetic system also promotes sexual arousal, including erection in males. Although the sympathetic and parasympathetic systems produce contrary effects, both are constantly active to varying degrees, and many stimuli arouse parts of both systems.The parasympathetic nervous system is also known as the craniosacral system because it consists of the cranial nerves and nerves from the sacral spinal cord (see Figure 3.6). Unlike the ganglia in the sympathetic system, the parasympathetic ganglia are not arranged in a chain near the spinal cord. Rather, long preganglionic axons extend from the spinal cord to parasympathetic ganglia close to each internal organ. Shorter postganglionic fibers then extend from the parasympathetic ganglia into the organs themselves. Because the parasympathetic ganglia are not linked to one another, they act more independently than the sympathetic ganglia do. Parasympathetic activity decreases heart rate, increases digestive rate, and in general, conserves energy.The parasympathetic nervous system’s axons release the neurotransmitter acetylcholine onto the organs. Most sympathetic nervous system axons release norepinephrine, although a few, such as those onto the sweat glands, use acetylcholine. Because the two systems use different transmitters, certain drugs excite or inhibit one system or the other. For example, over-the-counter cold remedies exert most of their effects by blocking parasympathetic activity or increasing sympathetic activity. Because the flow of sinus fluids is a parasympathetic response, drugs that block the parasympathetic system inhibit sinus flow. The side effects of cold remedies stem from their pro-sympathetic, anti-parasympathetic activities: They increase heart rate, blood pressure, and arousal. They inhibit salivation and digestion. Certain decongestant pills containing pseudoephedrine have been withdrawn or restricted because of their potential for abuse.Figure 3.6   The sympathetic nervous system (red lines) and parasympathetic nervous system (blue lines)Note that the adrenal glands, sweat glands, and hair erector muscles receive sympathetic input only.STOP & CHECK5. Motor nerves leave from which side of the spinal cord, dorsal or ventral?6. Which functions are controlled by the sympathetic nervous system? Which are controlled by the parasympathetic nervous system?ANSWERS5. Ventral. 6. The sympathetic nervous system prepares the organs for vigorous fight-or-flight activity. The parasympathetic system increases vegetative responses such as digestion.The HindbrainThe brain has three major divisions—the hindbrain, the midbrain, and the forebrain (see Figure 3.7 and Table 3.3). Some neuroscientists prefer terms with Greek roots: rhombencephalon (hindbrain), mesencephalon (midbrain), and prosencephalon (forebrain). You may encounter these terms in other reading.The hindbrain, the posterior part of the brain, consists of the medulla, the pons, and the cerebellum. The medulla and pons, the midbrain, and certain central structures of the forebrain constitute the brainstem (see Figure 3.8).Figure 3.7   Major divisions of the vertebrate brainIn a fish brain, as shown here, the forebrain, midbrain, and hindbrain are clearly visible as separate bulges. In adult mammals, the forebrain grows and surrounds the entire midbrain and part of the hindbrain.The medulla, or medulla oblongata, can be regarded as an enlarged extension of the spinal cord. Just as the lower parts of the body connect to the spinal cord via sensory and motor nerves, the head and the organs connect to the medulla and adjacent areas by 12 pairs of cranial nerves (one of each pair on the right side and one on the left), as shown in Table 3.4 and Figure 3.9. The cranial nerves originating in the medulla control vital reflexes such as breathing, heart rate, vomiting, salivation, coughing, and sneezing. Because opiate receptors, which suppress activity, are abundant in the medulla, opiates can produce a dangerous decrease in breathing and heart rate.The pons lies anterior and ventral to the medulla. Like the medulla, it contains nuclei for several cranial nerves. The term pons is Latin for “bridge,” reflecting the fact that in the pons, axons from each half of the brain cross to the opposite side of the spinal cord so that the left hemisphere controls the muscles of the right side of the body and the right hemisphere controls the left side.The cerebellum is a large hindbrain structure with many deep folds. It has long been known for its contributions to the control of movement, and many older textbooks describe the cerebellum as important for “balance and coordination.” True, people with cerebellar damage are clumsy and lose their balance, but the functions of the cerebellum extend far beyond balance and coordination. People with damage to the cerebellum have trouble shifting their attention back and forth between auditory and visual stimuli (Courchesne et al., 1994). They have difficulty with timing, such as judging whether one rhythm is faster than another. The cerebellum is also critical for certain types of learning and conditioning.Table 3.3 Major Divisions of the Vertebrate BrainAreaAlso Known asMajor StructuresForebrainProsencephalon (“forward-brain”)Diencephalon (“between-brain”)Thalamus, hypothalamusTelencephalon (“end-brain”)Cerebral cortex, hippocampus, basal gangliaMidbrainMesencephalon (“middle-brain”)Tectum, tegmentum, superior colliculus, inferior colliculus, substantia nigraHindbrainRhombencephalon (literally, “parallelogram-brain”)Medulla, pons, cerebellumFigure 3.8   The human brainstemThis composite structure extends from the top of the spinal cord into the center of the forebrain. The cerebral cortex surrounds the thalamus, pineal gland, and midbrain.The MidbrainAs the name implies, early in development the midbrain is in the middle of the brain, although in adult mammals it is dwarfed and surrounded by the forebrain. The midbrain is more prominent in reptiles, amphibians, and fish. The roof of the midbrain is called the tectum. (Tectum is the Latin word for “roof.” The same root occurs in the geological term plate tectonics.) The swellings on each side of the tectum are the superior colliculus and the inferior colliculus (see Figures 3.8 and 3.10). Both are important for sensory processing—the inferior colliculus for hearing and the superior colliculus for vision.Under the tectum lies the tegmentum, the intermediate level of the midbrain. (In Latin, tegmentum means a “covering,” such as a rug on the floor. The tectum covers the tegmentum, but the tegmentum covers several other midbrain structures.) Another midbrain structure, the substantia nigra, gives rise to a dopamine-containing pathway that facilitates readiness for movement.Table 3.4 The Cranial NervesNumber and NameMajor Functions I. OlfactoryII. OpticSmellVisionIII. OculomotorIV. TrochlearControl of eye movements; pupil constrictionControl of eye movementsV. TrigeminalSkin sensations from most of the face; control of jaw muscles for chewing and swallowingVI. AbducensControl of eye movementsVII. FacialTaste from the anterior two thirds of the tongue; control of facial expressions, crying, salivation, and dilation of the head’s blood vesselsVIII. StatoacousticHearing; equilibriumIX. GlossopharyngealTxaste and other sensations from throat and posterior third of the tongue; control of swallowing, salivation, throat movements during speechX. VagusXI. AccessorySensations from neck and thorax; control of throat, esophagus, and larynx; parasympathetic nerves to stomach, intestines, and other organsControl of neck and shoulder movementsXII. HypoglossalControl of muscles of the tongueCranial nerves III, IV, and VI are coded in red to highlight their similarity: control of eye movements. Cranial nerves VII, IX, and XII are coded in green to highlight their similarity: taste and control of tongue and throat movements. Cranial nerve VII has other important functions as well. Nerve X (not highlighted) also contributes to throat movements, although it is primarily known for other functions.Figure 3.9   Cranial nerves II through XIICranial nerve I, the olfactory nerve, connects directly to the olfactory bulbs of the forebrain.The ForebrainThe forebrain, the most prominent part of the mammalian brain, consists of two cerebral hemispheres, one on the left and one on the right (see Figure 3.11). Each hemisphere is organized to receive sensory information, mostly from the contralateral (opposite) side of the body. It controls muscles, mostly on the contralateral side, by way of axons to the spinal cord and the cranial nerve nuclei.The outer portion is the cerebral cortex. (Cerebrum is a Latin word for “brain.” Cortex is a Latin word for “bark” or “shell.”) Under the cerebral cortex are other structures, including the thalamus and the basal ganglia. Several interlinked structures, known as the limbic system, form a border (or limbus, the Latin word for “border”) around the brainstem. The limbic system includes the olfactory bulb, hypothalamus, hippocampus, amygdala, and cingulate gyrus of the cerebral cortex. The hypothalamus is essential for control of eating, drinking, temperature control, and reproductive behaviors. The amygdala is part of the circuit that is most central for evaluating emotional information, especially with regard to fear. Figure 3.12 shows the positions of these structures in three-dimensional perspective. Figures 3.13 and 3.10 show coronal (from the front) and sagittal (from the side) sections through the human brain. Figure 3.13 also includes a view of the ventral surface of the brain.Figure 3.10   A sagittal section through the human brainFigure 3.11   Dorsal view of the brain surface and a horizontal section through the brainFigure 3.12   The limbic system is a set of subcortical structures that form a border (or limbus) around the brainstem.In describing the forebrain, let’s begin with the subcortical areas. The next module focuses on the cerebral cortex. Later chapters discuss certain areas in more detail as they become relevant.ThalamusThe thalamus and hypothalamus form the diencephalon, a section distinct from the telencephalon, which is the rest of the forebrain. The thalamus is a pair of structures (left and right) in the center of the forebrain. The term derives from a Greek word meaning “anteroom,” “inner chamber,” or “bridal bed.” It resembles two small avocados joined side by side, one in the left hemisphere and one in the right. Most sensory information goes first to the thalamus, which processes it and sends output to the cerebral cortex. An exception to this rule is olfactory information, which goes from the olfactory receptors to the olfactory bulbs and then directly to the cerebral cortex.Figure 3.13   Two views of the human brainLeft: A coronal section. Note how the corpus callosum and anterior commissure provide communication between the left and right hemispheres.Right: The ventral surface. The optic nerves (cut here) extend to the eyes.Figure 3.14   Routes of information from the thalamus to the cerebral cortexEach thalamic nucleus projects its axons to a different part of the cortex.Many nuclei of the thalamus receive their input from a sensory system, such as vision, and transmit information to a single area of the cerebral cortex, as in Figure 3.14. The cerebral cortex sends information back to the thalamus, prolonging and magnifying certain kinds of input and focusing attention on particular stimuli (Komura et al., 2001).Hypothalamus and Pituitary GlandThe hypothalamus, a small area near the base of the brain just ventral to the thalamus (see Figures 3.10 and 3.12), has widespread connections with the rest of the brain. The hypothalamus contains distinct nuclei, which we examine in the chapters on motivation and emotion. Partly through nerves and partly by releasing hormones, the hypothalamus conveys messages to the pituitary gland, altering its release of hormones. Damage to any hypothalamic nucleus leads to abnormalities in motivated behaviors, such as feeding, drinking, temperature regulation, sexual behavior, fighting, or activity level. Because of these important behavioral effects, the small hypothalamus attracts much research attention.The pituitary gland is an endocrine (hormone-producing) gland attached to the base of the hypothalamus (see Figure 3.10). In response to messages from the hypothalamus, the pituitary synthesizes hormones that the blood carries to organs throughout the body.Basal GangliaThe basal ganglia, a group of subcortical structures lateral to the thalamus, include three major structures: the caudate nucleus, the putamen, and the globus pallidus (see Figure 3.15). Some authorities include other structures as well.Figure 3.15   The basal gangliaThe thalamus is in the center, the basal ganglia are lateral to it, and the cerebral cortex is on the outside.It has long been known that damage to the basal ganglia impairs movement, as in conditions such as Parkinson’s disease and Huntington’s disease. The basal ganglia integrate motivational and emotional behavior to increase the vigor of selected actions. However, the role of the basal ganglia extends beyond movement. They are critical for learned skills and habits, as well as other types of learning that develop gradually with extended experience. We return to the basal ganglia in more detail in the chapters on movement and memory.Basal ForebrainOne of the structures on the ventral surface of the forebrain, the nucleus basalis, receives input from the hypothalamus and basal ganglia and sends axons that release acetylcholine to widespread areas in the cerebral cortex (see Figure 3.16). The nucleus basalis is a key part of the brain’s system for arousal, wakefulness, and attention, as we consider in the chapter on sleep. Patients with Parkinson’s disease and Alzheimer’s disease have impairments of attention and intellect because of inactivity or deterioration of their nucleus basalis.Figure 3.16   The basal forebrainThe nucleus basalis and other structures in this area send axons throughout the cortex, increasing its arousal and wakefulness through release of the neurotransmitter acetylcholine.HippocampusThe hippocampus (from the Latin word meaning “sea horse,” a shape suggested by the hippocampus) is a large structure between the thalamus and the cerebral cortex, mostly toward the posterior of the forebrain, as shown in Figure 3.12. We consider the hippocampus in more detail in the chapter on memory. The gist of that discussion is that the hippocampus is critical for certain types of memories, especially memories for individual events. It is also essential for monitoring where you are and where you are going.STOP & CHECK7. Of the following, which are in the hindbrain, which in the midbrain, and which in the forebrain: basal ganglia, cerebellum, hippocampus, hypothalamus, medulla, pituitary gland, pons, substantia nigra, superior and inferior colliculi, tectum, tegmentum, thalamus?8. Which area is the main source of input to the cerebral cortex?ANSWERS7. Hindbrain: cerebellum, medulla, and pons. Midbrain: substantia nigra, superior and inferior colliculi, tectum, and tegmentum. Forebrain: basal ganglia, hippocampus, hypothalamus, pituitary, and thalamus. 8. ThalamusThe VentriclesThe nervous system begins its development as a tube surrounding a fluid canal. The canal persists into adulthood as the central canal in the center of the spinal cord, and as the ventricles, four fluid-filled cavities within the brain. Each hemisphere contains one of the two large lateral ventricles (see Figure 3.17). Toward their posterior, they connect to the third ventricle, positioned at the midline, separating the left thalamus from the right thalamus. The third ventricle connects to the fourth ventricle in the center of the medulla.Cells called the choroid plexus along the walls of the four ventricles produce cerebrospinal fluid (CSF), a clear fluid similar to blood plasma. CSF fills the ventricles, flowing from the lateral ventricles to the third and fourth ventricles. From the fourth ventricle, some of it flows into the central canal of the spinal cord, but more goes into the narrow spaces between the brain and the thin meninges, membranes that surround the brain and spinal cord. In one of those narrow spaces, the subarachnoid space, the blood gradually reabsorbs the CSF. Although the brain has no pain receptors, the meninges do, and meningitis—inflammation of the meninges—is painful. Swollen blood vessels in the meninges are responsible for the pain of a migraine headache (Hargreaves, 2007).Cerebrospinal fluid cushions the brain against mechanical shock when the head moves. It also provides buoyancy. Just as a person weighs less in water than on land, cerebrospinal fluid helps support the weight of the brain. It also provides a reservoir of hormones and nutrition for the brain and spinal cord.Figure 3.17   The cerebral ventricles(a) Diagram showing positions of the four ventricles. (b) Photo of a human brain, viewed from above, with a horizontal cut through one hemisphere to show the position of the lateral ventricles.If the flow of CSF is obstructed, it accumulates within the ventricles or in the subarachnoid space, increasing pressure on the brain. When this occurs in infants, the skull bones spread, causing an overgrown head. This condition, known as hydrocephalus (HI-dro-SEFF-ah-luss), can lead to mental retardation, although the results vary from one person to another.Module 3.1 | In ClosingLearning NeuroanatomyThe brain is a complex structure. This module has introduced a great many terms and facts. Do not be discouraged if you have trouble remembering them. It will help to return to this module to review anatomy as you encounter structures again in later chapters. Gradually, the material will become more familiar.Summary1. The vertebrate nervous system has two main divisions, the central nervous system and the peripheral nervous system. 682. Each segment of the spinal cord has a sensory nerve and a motor nerve on both the left and right sides. Spinal pathways convey information to the brain. 703. The sympathetic nervous system (one of the two divisions of the autonomic nervous system) activates the body’s internal organs for vigorous activities. The parasympathetic system (the other division) promotes digestion and other nonemergency processes. 714. The central nervous system consists of the spinal cord, the hindbrain, the midbrain, and the forebrain. 725. The hindbrain consists of the medulla, pons, and cerebellum. The medulla and pons control breathing, heart rate, and other vital functions through the cranial nerves. The cerebellum contributes to movement, timing short intervals, and certain types of learning and conditioning. 726. The cerebral cortex receives its sensory information, except for olfaction, from the thalamus. 767. The subcortical areas of the forebrain include the thalamus, hypothalamus, pituitary gland, basal ganglia, and hippocampus. 768. The cerebral ventricles contain fluid that provides buoyancy and cushioning for the brain. 79Key TermsTerms are defined in the module on the page number indicated. They’re also presented in alphabetical order with definitions in the book’s Subject Index/Glossary, which begins on page 589. Interactive flash cards, audio reviews, and crossword puzzles are among the online resources available to help you learn these terms and the concepts they represent.amygdala 75autonomic nervous system 69basal ganglia 77brainstem 72central nervous system 68cerebellum 73cerebrospinal fluid (CSF) 79cranial nerves 73dorsal 69dorsal root ganglia 70forebrain 74gray matter 70hindbrain 72hippocampus 79hypothalamus 77inferior colliculus 73limbic system 74medulla 73meninges 79midbrain 73neuroanatomy 67nucleus basalis 78parasympathetic nervous system 71peripheral nervous system (PNS) 68pituitary gland 77pons 73somatic nervous system 69spinal cord 70substantia nigra 73superior colliculus 73sympathetic nervous system 71tectum 73tegmentum 73thalamus 76ventral 69ventricles 79white matter 71Thought QuestionBeing nervous interferes with sexual arousal. Explain why, with reference to the sympathetic and parasympathetic nervous systems.Module 3.1 | End of Module Quiz1. What does ventral mean?A. Toward the sideB. Toward the frontC. Toward the stomachD. Toward the head2. If two structures are both on the left side, or both on the right, what is their relationship?A. MedialB. VentralC. IpsilateralD. Contralateral3. What is a sulcus in the brain?A. A groove that separates one gyrus from anotherB. A fluid-filled cavityC. A set of axons from one brain structure to anotherD. A temporary decrease in activity4. What is the function of the dorsal roots of the spinal cord?A. They receive sensory input.B. They control motor output.C. They convey information from the brain to the spinal cord.D. They convey information from the spinal cord to the brain.5. What does the parasympathetic nervous system control?A. Fight-or-flight activitiesB. Vegetative activitiesC. Social behaviorD. Learned habits6. Which of these controls breathing, heart rate, and salivation?A. The hippocampusB. The cranial nervesC. The basal gangliaD. The pituitary gland7. Which of these is part of the forebrain?A. HippocampusB. MedullaC. PonsD. Cerebellum8. Which structure provides most of the direct input to the cerebral cortex?A. Cranial nervesB. MedullaC. ThalamusD. Pineal gland9. What do the ventricles contain?A. Densely packed neuron cell bodiesB. GliaC. Cerebrospinal fluidD. Long axonsAnswers: 1C, 2C, 3A, 4A, 5B, 6B, 7A, 8C, 9CModule 3.2The Cerebral CortexThe most prominent part of the mammalian brain is the cerebral cortex. The cells on the outer surface of the cerebral cortex are gray matter, and their axons extending inward are white matter (see Figure 3.13a). Neurons in each hemisphere communicate with neurons in the corresponding part of the other hemisphere through two bundles of axons, the corpus callosum (see Figures 3.10, 3.11, and 3.13) and the smaller anterior commissure (see Figure 3.13). Several other commissures (pathways across the midline) link subcortical structures.The basic organization of the cerebral cortex is remarkably similar across vertebrate species (Harris & Shepherd, 2015). The visual cortex is in the same place, the auditory cortex is in the same place, and so forth. However, brains vary enormously in size. The largest mammalian brains are 100,000 times larger than the smallest ones (Herculano-Houzel, 2011).If we compare mammalian species, we see differences in the size of the cerebral cortex and the degree of folding (see Figure 3.18). Compared to other mammals of comparable size, the primates—monkeys, apes, and humans—have a larger cerebral cortex, more folding, and more neurons per unit of volume (Herculano-Houzel, 2011). Larger animals, such as elephants, have larger brain size but also larger neurons and fewer neurons per unit of volume. Humans have almost three times as many neurons in the cerebral cortex as elephants have, although the elephant brain is more than twice as large (Herculano-Houzel et al., 2015). In Figure 3.19, the investigators arranged the insectivores and primates from left to right in terms of what percentage of their brain was devoted to the forebrain, including the cerebral cortex (Clark, Mitra, & Wang, 2001). They also inserted tree shrews, a species often considered intermediate between insectivores and primates. Note that as the proportion devoted to the forebrain increases, the relative sizes of the midbrain and medulla decrease. That is, humans and other primates have a larger cerebral cortex than other species do, in proportion to the rest of the brain.Curiously, the cerebellum occupies a nearly constant percentage—about 10 to 14 percent of the brain in most species (Herculano-Houzel et al., 2015). Most species have about four (mostly tiny) neurons in the cerebellum for every one in the cerebral cortex (Herculano-Houzel, 2011). Why? Good question. Elephants, however, have a much larger number of neurons in the cerebellum, proportional to the rest of the brain (Herculano-Houzel et al., 2015). Why? Another good question.Organization of the Cerebral CortexThe microscopic structure of the cells of the cerebral cortex varies from one cortical area to another, as does the density of neurons per volume (Collins, 2011). Much research has been directed toward understanding the relationship between structure and function.Figure 3.18   Comparison of mammalian brainsAll mammals have the same brain subareas in the same locations.Figure 3.19   Relative sizes of five brain components in insectivores and primatesThe forebrain composes a larger percentage of primate than insectivore brains. Note also the nearly constant fraction devoted to the cerebellum.In humans and most other mammals, the cerebral cortex contains up to six distinct laminae, layers of cell bodies that are parallel to the surface of the cortex and separated from each other by layers of fibers (see Figure 3.20). The laminae vary in thickness and prominence from one part of the cortex to another, and a given lamina may be absent from certain areas. Lamina V, which sends long axons to the spinal cord and other distant areas, is thickest in the motor cortex, which has the greatest control of the muscles. Lamina IV, which receives axons from the sensory nuclei of the thalamus, is prominent in the sensory areas of the cortex (visual, auditory, and somatosensory) but absent from the motor cortex.The cells of the cortex are also organized into columns of cells perpendicular to the laminae. Figure 3.21 illustrates the idea of columns, although in nature they are not so straight. The cells within a given column have similar properties to one another. For example, if one cell in a column responds to touch on the palm of the left hand, then the other cells in that column do, too. If one cell responds to a horizontal pattern of light at a particular location, then other cells in the column respond to the same pattern in nearby locations.We now turn to specific parts of the cortex. Researchers make fine distinctions among areas of the cerebral cortex based on the structure and function of cells. For convenience, we group these areas into four lobes named for the skull bones that lie over them: occipital, parietal, temporal, and frontal.Figure 3.20   The six laminae of the human cerebral cortexFigure 3.21   Columns in the cerebral cortexEach column extends through several laminae. Neurons within a given column have similar properties. For example, in the somatosensory cortex, all the neurons within a given column respond to stimulation of the same area of skin.STOP & CHECK9. If several neurons of the visual cortex all respond best when the retina is exposed to horizontal lines of light, then those neurons are probably in the same _____.ANSWER9. columnThe Occipital LobeThe occipital lobe, at the posterior (caudal) end of the cortex (see Figure 3.22), is the main target for visual information. The posterior pole of the occipital lobe is known as the primary visual cortex, or striate cortex, because of its striped appearance in cross section. Destruction of any part of the striate cortex causes cortical blindness in the related part of the visual field. For example, extensive damage to the striate cortex of the right hemisphere causes blindness in the left visual field (that is, the left side of the world from the viewer’s perspective). A person with cortical blindness has normal eyes and pupillary reflexes, but no conscious visual perception and no visual imagery (not even in dreams). People who suffer eye damage become blind, but if they have an intact occipital cortex and previous visual experience, they can still imagine visual scenes and can still have visual dreams (Sabo & Kirtley, 1982). In short, the eyes provide the stimulus, and the visual cortex provides the experience.The Parietal LobeThe parietal lobe lies between the occipital lobe and the central sulcus, a deep groove in the surface of the cortex (see Figure 3.23). The area just posterior to the central sulcus, the postcentral gyrus, or primary somatosensory cortex, receives sensations from touch receptors, muscle-stretch receptors, and joint receptors. Brain surgeons sometimes use only local anesthesia—that is, anesthetizing the scalp but leaving the brain awake. If during this process they lightly stimulate the postcentral gyrus, people report tingling sensations on the opposite side of the body.The postcentral gyrus includes four bands of cells parallel to the central sulcus. Separate areas along each band receive simultaneous information from different parts of the body, as shown in Figure 3.23a (Nicolelis et al., 1998). Two of the bands receive mostly light-touch information, one receives deep-pressure information, and one receives a combination of both (Kaas, Nelson, Sur, Lin, & Merzenich, 1979). In effect, the postcentral gyrus represents the body four times.Figure 3.22   Areas of the human cerebral cortex(a) The four lobes: occipital, parietal, temporal, and frontal. (b) The primary sensory cortex for vision, hearing, and body sensations; the primary motor cortex; and the olfactory bulb, responsible for the sense of smell.Figure 3.23   Approximate representation of sensory and motor information in the cortex(a) Each location in the somatosensory cortex represents sensation from a different body part. (b) Each location in the motor cortex regulates movement of a different body part.Information about touch and body location is important not only for its own sake but also for interpreting visual and auditory information. For example, if you see something in the upper-left portion of the visual field, your brain needs to know which direction your eyes are turned, the position of your head, and the tilt of your body before it can determine the location of whatever you see. The parietal lobe monitors all the information about eye, head, and body positions and passes it on to brain areas that control movement. The parietal lobe is essential not only for spatial information but also numerical information (Hubbard, Piazza, Pinel, & Dehaene, 2005). That overlap makes sense when you consider all the ways in which numbers relate to space—including the fact that we initially use our fingers to count.The Temporal LobeThe temporal lobe is the lateral portion of each hemisphere, near the temples (see Figure 3.22). It is the primary cortical target for auditory information. The human temporal lobe—in most cases, the left temporal lobe—is essential for understanding spoken language. The temporal lobe also contributes to complex aspects of vision, including perception of movement and recognition of faces. A tumor in the temporal lobe may give rise to elaborate auditory or visual hallucinations, whereas a tumor in the occipital lobe ordinarily evokes only simple sensations, such as flashes of light. When psychiatric patients report hallucinations, brain scans detect much activity in the temporal lobes (Dierks et al., 1999).The temporal lobes are also important for emotional and motivational behaviors. Temporal lobe damage can lead to a set of behaviors known as the Klüver-Bucy syndrome (named for the investigators who first described it). Previously wild and aggressive monkeys fail to display normal fears and anxieties after temporal lobe damage (Klüver & Bucy, 1939). They put almost anything they find into their mouths and attempt to pick up snakes and lighted matches (which intact monkeys consistently avoid). Interpreting this behavior is difficult. For example, a monkey might handle a snake because it is no longer afraid (an emotional change) or because it no longer recognizes what a snake is (a cognitive change). We explore these issues in the chapter on emotion.The Frontal LobeThe frontal lobe, containing the primary motor cortex and the prefrontal cortex, extends from the central sulcus to the anterior limit of the brain (see Figure 3.22). The posterior portion of the frontal lobe, the precentral gyrus, is specialized for the control of fine movements, such as moving a finger. Separate areas are responsible for different parts of the body, mostly on the contralateral (opposite) side but also with slight control of the ipsilateral (same) side. Figure 3.23b shows the traditional map of the precentral gyrus, also known as the primary motor cortex. No area in the motor cortex controls just a single muscle. If two muscles usually move together, such as the muscles controlling your little finger and your ring finger, then the brain areas that control one of them largely overlap those that control the other one (Ejaz, Hamada, & Diedrichsen, 2015).The most anterior portion of the frontal lobe is the prefrontal cortex. In general, species with a larger cerebral cortex devote a larger percentage of it to the prefrontal cortex (see Figure 3.24). For example, it forms a larger portion of the cortex in humans and the great apes than in other species (Semendeferi, Lu, Schenker, & Damasio, 2002). Neurons in the prefrontal cortex have huge numbers of synapses and integrate an enormous amount of information.STOP & CHECK10. Which lobe of the cerebral cortex includes the primary auditory cortex?11. Which lobe of the cerebral cortex includes the primary somatosensory cortex?12. Which lobe of the cerebral cortex includes the primary visual cortex?13. Which lobe of the cerebral cortex includes the primary motor cortex?ANSWERS10. Temporal lobe 11. Parietal lobe 12. Occipital lobe 13. Frontal lobeThe Rise and Fall of Prefrontal LobotomiesA horizontal section of the brain of a person who had a prefrontal lobotomy many years earlier. The two holes in the frontal cortex are the visible results of the operation.You probably have heard of the infamous procedure known as prefrontal lobotomy—surgical disconnection of the prefrontal cortex from the rest of the brain. The surgery consisted of damaging the prefrontal cortex or cutting its connections to the rest of the cortex. Lobotomy began with a report that damaging the prefrontal cortex of laboratory primates made them tamer without noticeably impairing their sensations or coordination. A few physicians reasoned loosely (!) that the same operation might help people who suffered from severe, untreatable psychiatric disorders.Figure 3.24   Species differences in prefrontal cortexNote that the prefrontal cortex (blue area) constitutes a larger proportion of the human brain than of these other species.In the late 1940s and early 1950s, at a time when legal and ethical restraints in medicine were lax, about 40,000 prefrontal lobotomies were performed in the United States (Shutts, 1982), many of them by Walter Freeman, a medical doctor untrained in surgery. His techniques were crude, even by the standards of the time, using such instruments as an electric drill and a metal pick. He performed many operations in his office or other nonhospital sites. (Freeman carried his equipment in his car, which he called his “lobotomobile.”)At first, Freeman and others limited the technique to people with severe schizophrenia, for which no effective treatment was available at the time. Later, Freeman lobotomized people with less serious disorders, including some people whom we would consider normal by today’s standards. After drug therapies became available in the mid-1950s, lobotomies quickly dropped out of favor.Among the common consequences of prefrontal lobot-omy were apathy, a loss of the ability to plan and take initiative, memory disorders, distractibility, and a loss of emotional expressions (Stuss & Benson, 1984). People with prefrontal damage lost their social inhibitions, ignoring the rules of polite, civilized conduct. They often acted impulsively because they failed to calculate adequately the probable outcomes of their behaviors.Functions of the Prefrontal CortexAn analysis of thousands of studies concluded that the prefrontal cortex has three major regions (de la Vega, Chang, Banich, Wager, & Yarkoni, 2016). The posterior portion is associated mostly with movement. The middle zone pertains to working memory, cognitive control, and emotional reactions. Working memory is the ability to remember recent events, such as where you parked your car or what you were talking about before an interruption. People with damage to the prefrontal cortex have trouble on the delayed-response task, in which they see or hear something, and then have to respond to it after a delay.The anterior zone of the prefrontal cortex is important for making decisions, evaluating which of several courses of action is likely to achieve the best outcome. When you decide whether to do something, you consider the difficulty of the action, the probabilities of success and failure, and how valuable the possible reward would be to you, all things considered. For example, the chance to win a pizza becomes less valuable if you have just finished a meal. An opportunity to win a few extra-credit points is valuable if you think you are on the borderline between two grades, but less valuable otherwise. If you have a choice between spending money now and saving it for later, you try to compare the possibility of current pleasure and the possible need for money later. Cells in the prefrontal cortex respond to all these complex factors (Hunt et al., 2012; Wallis, 2012). People with prefrontal cortical damage often make decisions that seem impulsive, because they failed to weigh all the likely pros and cons.STOP & CHECK14. What are the functions of the prefrontal cortex?ANSWER14. The posterior portion contributes to control of move-ment. The middle portion pertains to working memory, cognitive control, and emotion. The anterior portion compares various types of information for making a decision.How Do the Parts Work Together?Here is a theoretical issue that researchers hardly even considered before about 1990: How do various brain areas combine to produce a unified experience? When you eat something, you experience the smell in the nose, and the taste and touch on the tongue as a single experience (Stevenson, 2014). If you shake something that makes a noise, you perceive that what you see is also what you feel and what you hear. But how do you do that? Each of the senses activates a different area of the cortex, and those areas have only weak connections with one another.The question of how various brain areas produce a perception of a single object is known as the binding problem, or large-scale integration problem. In an earlier era, researchers thought that various kinds of sensory information converged onto what they called the association areas of the cortex. Their guess was that those areas associate one sensation with another, or current sensations with memories of previous experiences. Later research found that relatively few cells combine one sense with another (Blanke, 2012). Even when they do, they don’t fully answer the question of how we bind sensory information together. For example, certain neurons in the posterior temporal cortex both when you see a chain saw and when you hear the sound it makes, or both when you see a jackhammer and when you hear a jackhammer sound (Man, Kaplan, Damasio, & Meyer, 2012). But surely you weren’t born knowing what sound a chain saw or a jackhammer makes. Somehow those cells had to develop those properties through experience. Similarly, many neurons in the superior colliculus respond to more than one sensory system, but they constantly change their properties based on experience (Stein, Stanford, & Rowland, 2014).Although researchers cannot fully explain binding, they know what is necessary for it to occur: It occurs if you perceive two sensations as happening at the same time and in approximately the same place. For example, when a skilled ventriloquist says something and makes the dummy’s mouth move at the same time, you perceive the sound as coming from the dummy. As part of this illusion, the visual stimulus alters the response of the auditory cortex, so that the sound really does seem to come from the same location as the dummy’s mouth (Bonath et al., 2007; Bruns, Liebnau, & Röder, 2011). In contrast, if you watch a poorly dubbed foreign-language film, the lips do not move at the same time as the speech, and you perceive that the words did not come from those lips.Applying these principles, researchers arranged a camera to video someone’s back, and simultaneously sent the pictures to a three-dimensional display mounted to the person’s head, as in Figure 3.25. Imagine that you are the participant. As you view the video of your back, it appears to be 2 meters in front of you. Then someone strokes your back. You simultaneously feel the touch and see the action that appears to be 2 meters in front. After a while, you start perceiving your body as being 2 meters in front of you! When asked, “please return to your seat,” you walk to a spot displaced from the actual seat, as if you were actually 2 meters forward from your current position (Lenggenhager, Tadi, Metzinger, & Blanke, 2007).Figure 3.25   Where Am I?As someone stroked the person’s back, a video camera relayed the information so the person could view it, appearing to be a few feet ahead. After a few minutes, the person felt as if the body were in fact a few feet ahead of where it was.Suppose you see a light flash once while you hear two beeps. You will sometimes think you saw the light flash twice. If the tone is soft, you may experience the opposite: The tone beeps twice during one flash of light, and you think you heard only one beep. If you saw three flashes of light, you might think you heard three beeps (Andersen, Tiippana, & Sams, 2004). The near simultaneity of lights and sounds causes you to bind them and perceive an illusion that alters your perception of one or the other. Binding often fails if the displays are flashed very briefly or while the viewer is distracted (Holcombe & Cavanagh, 2001; Lehky, 2000).Here is another great demonstration (Robertson, 2005). Position yourself parallel to a large mirror, as in Figure 3.26, so that you see your right hand and its reflection in the mirror. Keep your left hand out of sight. Now repeatedly clench and unclench both hands in unison. Wiggle your fingers, touch your thumb to each finger, and so forth, in each case doing the same thing with both hands at the same time. You will continually feel your left hand doing the same thing you see the hand in the mirror doing, which (being the mirror image of your right hand) looks like your left hand. After 2 or 3 minutes, you may start to feel that the hand in the mirror is your own left hand.In a variant of this procedure, researchers arranged to touch someone’s real right hand and a rubber hand next to it, both at the same time and in the same way, allowing the person to see both hands. Within minutes, people reported feeling that they had two right hands, in addition to the unseen left hand (Guterstam, Petkova, & Ehrsson, 2011). So, the evidence indicates that we bind two experiences that occur at the same time. Still, the theoretical question remains of exactly how we do so.Figure 3.26   An illusion to demonstrate bindingClench and unclench both hands while looking at your right hand and its reflection in the mirror. Keep your left hand out of sight. After a couple of minutes, you may start to experience the hand in the mirror as being your own left hand.STOP & CHECK15. What is meant by the binding problem, and what is necessary for binding to occur?ANSWER15. The binding problem is the question of how the brain combines activity in different brain areas to produce unified perception and coordinated behavior. Binding requires identifying the location of an object and perceiv-ing sight, sound, and other aspects of a stimulus as being simultaneous. When the sight and sound appear to come from the same location at the same time, we bind them as a single experience.Module 3.2 | In ClosingFunctions of the Cerebral CortexThe cerebral cortex is the largest portion of the human brain, but it is not the entire brain. What is its function? The primary function seems to be one of elaborating sensory information and organizing sequences of behaviors. Even fish, which have no cerebral cortex, can see, hear, and so forth, but the cerebral cortex enables us to add great complexity to our behavior.Summary1. Although brain size varies among mammalian species, the overall organization is similar. 822. The cerebral cortex has six laminae (layers) of neurons. A given lamina may be absent from certain parts of the cortex. For example, the lamina responsible for sensory input is absent from the motor cortex. The cortex is organized into columns of cells arranged perpendicular to the laminae. 833. The occipital lobe of the cortex is primarily responsible for vision. Damage to part of the occipital lobe leads to blindness in part of the visual field. 844. The parietal lobe processes body sensations. The postcentral gyrus contains four representations of the body. 845. The temporal lobe contributes to hearing, complex aspects of vision, and processing of emotional information. 856. The frontal lobe includes the precentral gyrus, which controls fine movements. It also includes the prefrontal cortex. 857. The prefrontal cortex is important for planning actions, working memory, certain aspects of emotion, and decision making. 878. The binding problem is the question of how we connect activities in different brain areas, such as sights and sounds. Binding requires perceiving that two aspects of a stimulus (such as sight and sound) occurred at the same place at the same time. 87Key TermsTerms are defined in the module on the page number indicated. They’re also presented in alphabetical order with definitions in the book’s Subject Index/Glossary, which begins on page 589. Interactive flash cards, audio reviews, and crossword puzzles are among the online resources available to help you learn these terms and the concepts they represent.anterior commissure 82binding problem 87central sulcus 84cerebral cortex 82columns 83corpus callosum 82delayed-response task 87frontal lobe 85Klüver-Bucy syndrome 85laminae 83occipital lobe 84parietal lobe 84postcentral gyrus 84precentral gyrus 85prefrontal cortex 86prefrontal lobotomy 86primates 82temporal lobe 85Thought QuestionWhen monkeys with Klüver-Bucy syndrome pick up lighted matches and snakes, we do not know whether they are displaying an emotional deficit or an inability to identify the object. What kind of research method might help answer this question?Module 3.2 | End of Module Quiz1. What is the main way in which mammalian species vary in their cerebral cortex?A. The locations of visual and auditory cortex vary among species.B. Some mammals have a cerebral cortex and some do not.C. Brains differ in their size and degree of folding.D. The number of laminae varies from 2 to 12.2. In which of these ways do primates differ from elephants in their cerebral cortex?A. Primates have more neurons per unit volume.B. Primates have a larger volume of cerebral cortex.C. The average size of neurons is greater in primates.D. The average length of axons is greater in primates.3. What is the relationship between columns and laminae in the cerebral cortex?A. Each column contains one and only one lamina.B. Each column crosses through one lamina after another.C. Some parts of the cortex have columns and others have laminae.D. A column is just another word for a lamina.4. Where is the primary visual cortex?A. Temporal lobeB. Frontal lobeC. Parietal lobeD. Occipital lobe5. Where is the primary somatosensory visual cortex?A. Temporal lobeB. Frontal lobeC. Parietal lobeD. Occipital lobe6. Where is the primary auditory cortex?A. Temporal lobeB. Frontal lobeC. Parietal lobeD. Occipital lobe7. Where is the primary motor cortex?A. Temporal lobeB. Frontal lobeC. Parietal lobeD. Occipital lobe8. The main functions of the prefrontal cortex include which of the following?A. Perceiving the location of body parts in spaceB. Providing a pool of immature neurons to replace those damaged in other brain areasC. Controlling reflexesD. Working memory and weighing the pros and cons of a possible action9. What is the binding problem?A. The difficulty of coordinating the left side of the body with the right sideB. The difficulty of synchronizing output from a population of axonsC. The question of how we perceive separate sensations as part of a single objectD. The question of how a bilingual person shifts from one language to anotherAnswers: 1C, 2A, 3B, 4D, 5C, 6A, 7B, 8D, 9C.Module 3.3Research MethodsDescribing the structure of the brain does not advance our knowledge of biological psychology until we discover how it works. Throughout this text, we shall consider many methods of relating the brain’s structure to its function. However, most methods fall into a few categories. This module provides an overview of those categories and the logic behind them:1. Examine the effects of brain damage. After damage or temporary inactivation, what aspects of behavior are impaired?2. Examine the effects of stimulating a brain area. Ideally, if damaging some area impairs a behavior, stimulating that area should enhance the behavior.3. Record brain activity during behavior. We might record changes in brain activity during fighting, sleeping, finding food, solving a problem, or any other behavior.4. Correlate brain anatomy with behavior. Do people with some unusual behavior also have unusual brains? If so, in what way?Effects of Brain DamageIn 1861, the French neurologist Paul Broca found that a patient who had lost the ability to speak had damage in part of his left frontal cortex. Additional patients with loss of speech also showed damage in and around that area, now known as Brocas area. Although much more research was necessary to explore the functions of that area, its discovery revolutionized neurology, as many other physicians at the time had doubted that different brain areas had different functions at all.Since then, researchers have made countless reports of behavioral impairments after brain damage. Brain damage can produce an inability to recognize faces, an inability to perceive motion, a shift of attention to the right side of the world, changes in motivation and emotion, memory impairments, and a host of other specialized effects. The implications are deep: If you lose part of your brain, you lose part of your mind.Many of the most interesting results come from humans with brain damage, but human studies have their limitations. Few people have damage confined to just one brain area, and each person’s pattern of brain damage is unique. Therefore, researchers often turn to producing carefully localized damage in laboratory animals. An ablation is the removal of a brain area, generally with a surgical knife. Because surgical removal is difficult for tiny structures below the surface of the brain, researchers sometimes make a lesion, meaning damage, by means of a stereotaxic instrument, a device for the precise placement of electrodes in the brain (see Figure 3.27). By consulting a stereotaxic atlas (map) of a species’ brain, a researcher aims an electrode at the desired position relative to landmarks on the skull. The researcher anesthetizes an animal, drills a small hole in the skull, inserts the electrode (insulated except at the tip), lowers it to the target, and passes an electrical current just sufficient to damage that area. For example, researchers have made lesions in parts of the hypothalamus to explore their contributions to eating and drinking. After the death of the animal, someone takes slices of its brain, applies stains, and verifies the actual location of the damage.Figure 3.27   A stereotaxic instrument for locating brain areas in small animalsUsing this device, researchers can insert an electrode to stimulate, record from, or damage any point in the brain.Suppose a researcher makes a lesion and reports some behavioral deficit. You might ask, “How do we know the deficit wasn’t caused by anesthetizing the animal, drilling a hole in its skull, and lowering an electrode to this target?” To test this possibility, an experimenter produces a sham lesion in a control group, performing all the same procedures except for passing the electrical current. Any behavioral difference between the two groups must result from the lesion and not the other procedures.An electric lesion is a crude technique that damages the axons passing through as well as the neurons in the area itself. Researchers use this method less often today than in the past. Instead, they might inject a chemical that kills neurons, or disables them temporarily, without harming the passing axons. They can also inject a chemical that disables a particular type of synapse. Another option is the gene-knockout approach that directs a mutation to a gene that regulates one type of cell, transmitter, or receptor.Transcranial magnetic stimulation (TMS), the application of magnetic stimulation to a portion of the scalp, can stimulate neurons in the area below the magnet, if the stimulation is sufficiently brief and mild. With stronger stimulation it inactivates the neurons, producing a “virtual lesion” that outlasts the magnetic stimulation itself (Dayan, Censor, Buch, Sandrini, & Cohen, 2013). This procedure enables researchers to study behavior with some brain area active, then inactive, and then active again. Figure 3.28 shows the apparatus. For example, one study found that after TMS silenced the hand area of the motor cortex, people had trouble with a task of mentally rotating the hand in a picture to imagine how it would look from a different angle (Ganis, Keenan, Kosslyn, & Pascual-Leone, 2000). That is, when you imagine seeing your hand from a different angle, you imagine moving it, not just seeing it move.After any kind of brain damage or inactivation, the problem for psychologists is to specify the exact behavioral deficit. For example, if you damage a brain area and the animal stops eating, you don’t know why. Did it lose its hunger? Its ability to taste food? Its ability to find the food? Its ability to move at all? You would need further behavioral tests to explore the possibilities.STOP & CHECK16. What is the difference between a lesion and an ablation?ANSWER16. A lesion is damage to a structure. An ablation is removal of the structure. For example, a blood clot might produce a lesion, whereas surgery could produce an ablation.Figure 3.28   Apparatus for magnetic stimulation of a human brainThe procedure is known as transcranial magnetic stimulation, or TMS.Effects of Brain StimulationIf brain damage impairs some behavior, stimulation should increase it. The old-fashioned way is to insert an electrode into an animal’s brain and deliver brief, mild currents to stimulate one area or another. That method has limited value, because a given area has many types of neurons with varying functions. The electrical current stimulates all of them, as well as passing axons.A popular approach today is optogenetics, using light to control a limited population of neurons. Development of this method required three steps, each of which would be useless without the others, and each of which seemed almost impossible. Despite the enormous reasons for pessimism, Karl Deisseroth and his colleagues persisted in efforts for years, until the method was ready for wide use in 2009 (Deisseroth, 2015).Karl Deisseroth[A] final point [is] the essential value of exploratory basic science research. … It seems unlikely that the initial experiments described here would have been fundable, as such, by typical grant programs focusing on a disease state. … [T]he advances brought by microbial opsin-based optogenetics may inform the pathophysiology of neurological and psychiatric disease states . . . in addition to the broad basic science discoveries. (Deisseroth, 2015, p. 1224)The first step was to discover or invent a protein that responds to light by producing an electrical current. Certain microbes do produce such proteins, which researchers have found ways to modify. One protein reacts to light by opening a sodium channel, exciting the neuron, and another reacts by opening a chloride channel, producing inhibition. The second step was to develop viruses that insert one of these proteins into a certain type of neuron, or even to just one part of the neuron, such as the axon or the dendrites (Packer, Roska, & Hausser, 2013). The third step was to develop very thin optical fibers that can shine just the right amount of light onto neurons in a narrowly targeted brain area.Using these methods, an investigator can control the excitation or inhibition of one type of neuron in a small brain area with millisecond accuracy. Thus, researchers can study the function of given cells in greater detail than ever before. A few physicians have begun applying optogenetics to human patients to try to control narcolepsy (a sleep disorder) and other medical or psychiatric conditions.The success of optogenetics has inspired related methods that can stimulate particular types of neurons by magnetic fields or by chemical injections (Smith, Bucci, Luikart, & Mahler, 2016; Wheeler et al., 2016). These methods activate larger numbers of neurons at one time than optogenetic methods do.STOP & CHECK17. What determines whether optogenetic stimulation excites a neuron or inhibits it?ANSWER17. Optogenetic stimulation activates a light-sensitive protein. If that protein opens a sodium channel in the membrane, the result is excitation of the neuron. If it opens a chloride channel, the result is inhibition.Recording Brain ActivitySuppose damage to some brain area impairs a behavior (eating, for example) and stimulation of that area increases the behavior. We can strengthen the conclusion by showing that the area increases its activity during spontaneous occurrences of the behavior. We might also use brain recordings for exploratory purposes: During a given behavior or cognitive activity, which brain areas increase their activity?With laboratory animals, one method is to insert an electrode to record activity from a single neuron. We shall consider examples of this method in the chapter on vision. New technologies enable researchers to record from tens to hundreds of neurons simultaneously (Luczak, McNaughton, & Harris, 2015).On rare occasions, researchers insert an electrode into a human neuron to record its activity, when the brain is exposed preliminary to brain surgery. Much more frequently, human research relies on noninvasive methods—that is, recordings from outside the skull. An electroencephalograph (EEG) records electrical activity of the brain through electrodes— ranging from just a few to more than a hundred—attached to the scalp (see Figure 3.29). Electrodes glued to the scalp measure the average activity at any moment for the population of cells under the electrode. The output is then amplified and recorded. An EEG is useful for distinguishing between wakefulness and various stages of sleep. It can also help with the diagnosis of epilepsy, although a physician may need to conduct the test repeatedly or test the person under special conditions before seeing the abnormal EEG pattern that is characteristic of epilepsy (Renzel, Baumann, & Poryazova, 2016; Salinsky, Kanter, & Dasheiff, 1987).The same device used for an EEG can also record brain activity in response to a stimulus, in which case we call the results evoked potentials or evoked responses. Evoked responses are useful for many purposes, including studies of infants too young to give verbal answers (Parise & Csibra, 2012).Figure 3.29   ElectroencephalographyAn electroencephalograph records the overall activity of neurons under various electrodes attached to the scalp.A magnetoencephalograph (MEG) is similar, but instead of measuring electrical activity, it measures the faint magnetic fields generated by brain activity (Hari, 1994). Like EEG, an MEG recording identifies the approximate location of activity to within about a centimeter. An MEG has excellent temporal resolution, showing changes from one millisecond to the next.Figure 3.30 shows an MEG record of brain responses to a brief tone heard in the right ear. The diagram represents a human head as viewed from above, with the nose at the top (Hari, 1994). Researchers using an MEG can identify the times at which various brain areas respond and thereby trace a wave of brain activity from its point of origin to the other areas that process it (Salmelin, Hari, Lounasmaa, & Sams, 1994).Positron-emission tomography (PET) provides a highresolution image of activity in a living brain by recording the emission of radioactivity from injected chemicals. First, the person receives an injection of glucose or some other chemical containing radioactive atoms. Because the most active brain areas increase their use of glucose, tracking the levels of glucose tells us something about brain activity. When a radioactive atom decays, it releases a positron that immediately collides with a nearby electron, emitting two gamma rays in opposite directions. The person’s head is surrounded by a set of gamma ray detectors (see Figure 3.31). When two detectors record gamma rays at the same time, they identify a spot halfway between those detectors as the point of origin of the gamma rays. A computer uses this information to determine how many gamma rays came from each spot in the brain and therefore how much of the radioactive chemical is located in each area (Phelps & Mazziotta, 1985). The areas with the most radioactivity are presumably the ones with the most active neurons.Figure 3.30   A result of magnetoencephalography, showing responses to a tone in the right earThe nose is shown at the top. For each spot on the diagram, the display shows the changing response over a few hundred milliseconds following the tone. (Note calibration at lower right.) The tone evoked responses in many areas, with the largest responses in the temporal cortex, especially on the left side.Figure 3.31   A PET scannerA person engages in a cognitive task while attached to this apparatus that records which areas of the brain become more active and by how much.PET scans use radioactive chemicals with a short half-life, made in a device called a cyclotron. Because cyclotrons are expensive, PET is available only at research hospitals. Furthermore, PET requires exposing the brain to radioactivity, a potential hazard. For most purposes, researchers have replaced PET scans with functional magnetic resonance imaging (fMRI), which is less expensive and less risky. Standard MRI scans record the energy released by water molecules after removal of a magnetic field. (We consider more details about this method later.) An fMRI is a modified version of MRI based on hemoglobin (the blood protein that binds oxygen) instead of water (Detre & Floyd, 2001). Hemoglobin with oxygen reacts to a magnetic field differently from hemoglobin without oxygen. Researchers set the fMRI scanner to detect the amount of hemoglobin with oxygen (Viswanathan & Freeman, 2007). When a brain area becomes more active, two relevant changes occur: First, blood vessels dilate to allow more blood flow to the area. Second, as the brain area uses oxygen, the percentage of hemoglobin with oxygen decreases. An fMRI scan responds to both of these processes (Sirotin, Hillman, Bordier, & Das, 2009). Figure 3.32 shows an example.Figure 3.32   An fMRI scan of a human brainAn fMRI produces an image with a spatial resolution of 1 to 2 mm and temporal resolution of about a second.An fMRI while you were, for example, reading would mean nothing without a comparison to something else. Researchers would record your brain activity while you were reading and during a comparison task and then subtract the brain activity during the comparison task to determine which areas are more active during reading. As a comparison task, for example, researchers might ask you to look at a page written in a language you do not understand. That task would activate visual areas just as the reading task did, but it presumably would not activate the language areas of your brain. Figure 3.33 illustrates the idea.The fMRI method produces spectacular pictures, but difficulties arise when we interpret the results (Rugg & Thompson-Schill, 2013). Researchers often examine the mean results for a group of participants, ignoring important differences among individuals (Finn et al., 2015). More importantly, researchers sometimes make the mistake of assuming that if an area is active during some psychological process, then its activity always indicates that process. For example, certain types of reward activate a brain area called the dorsal striatum (part of the basal ganglia). If the dorsal striatum becomes active while people are doing something, does that activity mean that people find the activity rewarding? Not necessarily, unless we know that the dorsal striatum is active only as a function of reward (Poldrack, 2006). Most brain areas participate in several functions.The best way to test our understanding of fMRI results is to see whether the inference we make from a recording matches what someone is actually doing or thinking. That is, we should be able to use it to read someone’s mind, to a limited degree. A few examples of success have been reported. For example, researchers used fMRI to record brain activity from people as they were falling asleep. People typically have some visual imagery at that time, but not quite a dream. The researchers repeatedly awakened these people, asked them to report their visual images, and compared the reports to the fMRI data. After enough repetitions, they were able to use the fMRI data to predict approximately what imagery the people were about to report (Horikawa, Tamaki, Miyawaki, & Kamitani, 2013). In another study, people learned to use a mental code to spell out words. For example, if you waited 10 seconds and then performed mental math calculations for 20 seconds, that combination meant the letter M. Using an fMRI, researchers could identify the word the person wanted to express (Sorger, Reithler, Dahmen, & Goebel, 2012). Don’t worry. No one could use this method to read your mind without your enthusiastic cooperation. Researchers need to calibrate the equipment over many trials to know what your particular fMRI results mean. The main point is that under limited circumstances, we can indeed use an fMRI to infer someone’s psychological processes.Figure 3.33   Subtraction for a brain scan procedureNumbers on the brain at the left show hypothetical levels of arousal during some task, measured in arbitrary units. The brain at the center shows activity during the same brain areas during a comparison task. The brain at the right shows the differences. The highlighted area shows the largest difference. In actual data, the largest increases in activity would be one-tenth or two-tenths of a percent.Most fMRI studies have concentrated on identifying the functions of brain areas, rather than contributing to our understanding of psychology (Coltheart, 2013). Nevertheless, fMRI does sometimes provide valuable psychological information. Here are a few examples:1. Many people in pain report decreased pain after they receive a placebo (a drug with no pharmacological activity). Do they really feel less pain, or are they just saying so? Studies with fMRI show that brain areas responsible for pain really do decrease their response (Wager & Atlas, 2013).2. Psychologists find it useful to distinguish several types of memory, such as implicit versus explicit and declarative versus procedural. One view is that any given task falls into one category or the other. In that case, we might expect that one type of memory activates one set of brain areas and another type activates other areas. An alternative view is that we process memory with several components, some of which pertain mostly to one type of memory and others that pertain mostly to a different type of memory. The fMRI data fit that view better: Most memory tasks activate a wide array of brain areas to varying degrees (Cabeza & Moscovitch, 2013).3. When you are just sitting there with nothing expected of you, is your brain really doing nothing? Definitely not. You do “mind wandering,” which activates diffuse areas called the brain’s default system (Corballis, 2012b; Mason et al., 2007). These same areas are also active when people recall past experiences or imagine future experiences (Immordino-Yang, Christodoulou, & Singh, 2012).STOP & CHECK18. What does fMRI measure?19. Suppose someone demonstrates that a particular brain area becomes active when people are listening to music. When that area becomes active later, what if anything can we conclude?ANSWERS18. It detects an increase in blood flow to a brain area immediately after an increase in brain activity, and it also detects a slightly slower increase in the percentage of hemoglobin lacking oxygen. 19. Without further evidence, we should not draw any conclusion. Perhaps the person is listening to music or imagining music, but this area may perform functions other than music. We would need to test how accurately we can use the fMRI data to predict what the person is doing or imagining.Correlating Brain Anatomy with BehaviorOne of the first ways ever used for studying brain function sounds easy: Find someone with unusual behavior and then look for unusual features of the brain. In the 1800s, Franz Gall observed some people with excellent verbal memories who had protruding eyes. He inferred that verbal memory depended on brain areas behind the eyes that had pushed the eyes forward. Gall then examined the skulls of people with other talents or personalities. He assumed that bulges and depressions on their skull corresponded to the brain areas below them. His process of relating skull anatomy to behavior is known as phrenology. One of his followers made the phrenological map in Figure 3.34.Phrenology was invalid for many reasons. One problem was that skull shape does not match brain anatomy. The skull is thicker in some places than others and thicker in some people than others. Another problem was that they based many conclusions on small numbers of people who apparently shared some personality aspect and a similar bump on the skull.Today, researchers examine detailed brain anatomy in living people. One method is computerized axial tomography better known as a CT or CAT scan (Andreasen, 1988). A physician injects a dye into the blood to increase contrast in the image, and then places the person’s head into a CT scanner like the one shown in Figure 3.35a. X-rays are passed through the head and recorded by detectors on the opposite side. The CT scanner is rotated slowly until a measurement has been taken at each angle over 180 degrees. From the measurements, a computer constructs images of the brain. Figure 3.35b is an example. CT scans help detect tumors and other structural abnormalities.Another method is magnetic resonance imaging (MRI) (Warach, 1995), based on the fact that any atom with an odd-numbered atomic weight, such as hydrogen, has an axis of rotation. An MRI device applies a powerful magnetic field (about 25,000 times the magnetic field of the Earth) to align all the axes of rotation, and then tilts them with a brief radio frequency field. When the radio frequency field is turned off, the atomic nuclei release electromagnetic energy as they relax and return to their original axis. By measuring that energy, MRI devices form an image of the brain, such as the one in Figure 3.36. MRI shows anatomical details smaller than a millimeter in diameter. One drawback is that the person must lie motionless in a confining, noisy apparatus. The procedure is usually not suitable for children or anyone who fears enclosed places.Figure 3.34   A phrenologist’s map of the brainNeuroscientists today also try to localize functions in the brain, but they use more careful methods and they study such functions as vision and hearing, not “secretiveness” and “marvelousness.”Researchers using these methods sometimes find that a particular brain area is enlarged in certain types of people. For example, it has been reported that people with a larger amygdala tend to have more social contacts (Bickart, Wright, Dautoff, Dickerson, & Barrett, 2011). Personality traits such as extraversion, neuroticism, and conscientiousness correlate significantly with the size of certain areas of the cortex (De Young et al., 2010). Certain aspects of executive function (cognitive control of behavior) correlate with the amount of white matter connecting three parts of the prefrontal cortex to other brain areas (Smolker, Depue, Reineberg, Orr, & Banich, 2015). Adolescents with a large vocabulary tend to have more than average gray matter in part of the parietal lobe (Lee et al., 2007).Figure 3.35   CT scanner(a) A person’s head is placed into the device and then a rapidly rotating source sends X-rays through the head while detectors on the opposite side make photographs. A computer then constructs an image of the brain. (b) A view of a normal human brain generated by computerized axial tomography (CT scanning).Figure 3.36   A view of a living brain generated by magnetic resonance imagingAny atom with an odd-numbered atomic weight, such as hydrogen, has an inherent rotation. An outside magnetic field can align the axes of rotation. A radio frequency field can then make all these atoms move like tiny gyros. When the radio frequency field is turned off, the atomic nuclei release electromagnetic energy as they relax. By measuring that energy, we can obtain an image of a structure such as the brain without damaging it.However, we need to examine correlations like these with caution. Many of the studies have used small, possibly unrepresentative samples, and many reports relating brain anatomy to behavior have been hard to replicate (Boekel et al., 2015). Because of the tendency to publish what appear to be positive results and ignore negative results, conclusions based on small samples are sometimes wrong, or at least overstatements of small effects. Table 3.5 summarizes various methods of studying brain-behavior relationships.STOP & CHECK20. What are the similarities and differences between MRI and fMRI?ANSWER20. Both methods measure the responses of brain chemicals to a magnetic field. MRI shows the anatomy of the brain. The fMRI method shows which brain areas are most active at the moment.Table 3.5 Methods of Studying Brain-Behavior RelationshipsExamine Effects of Brain DamageStudy victims of stroke, etc.Used with humans; each person has different damageLesionControlled damage in laboratory animalsAblationRemoval of a brain areaGene knockoutAffects wherever that gene is active (e.g., a receptor)Transcranial magnetic stimulationIntense application temporarily inactivates a brain areaExamine Effects of Stimulating a Brain AreaStimulating electrodesInvasive; used with laboratory animals, rarely with humansOptogenetic stimulationMostly with laboratory animals; can indicate function of a particular type of cellRecord Brain Activity during BehaviorRecord from electrodes in brainInvasive; used with laboratory animals, rarely with humansElectroencephalograph (EEG)Records from scalp; measures changes by milliseconds, but with low resolution of location of the signalEvoked potentialsSimilar to EEG but in response to stimuliMagnetoencephalograph (MEG)Similar to EEG but measures magnetic fieldsPositron emission tomography (PET)Measures changes over both time and location but requires exposing brain to radiationFunctional magnetic resonance imaging (fMRI)Measures changes over about 1 second, identifies location within 1 to 2 mmCorrelate Brain Anatomy with BehaviorComputerized axial tomography (CAT)Maps brain areas, but requires exposure to X-raysMagnetic resonance imaging (MRI)Maps brain areas in detail, using magnetic fieldsModule 3.3 | In ClosingResearch Methods and ProgressIn any scientific field—indeed, any field of knowledge— progress almost always depends on improvements in measurement. In astronomy, for example, improvements in both ground-based and satellite-based astronomy have established conclusions that even science-fiction writers couldn’t have imagined a few decades ago. Weather prediction is vastly more accurate than it used to be. Similarly, our understanding of the brain has advanced greatly because of the introduction of PET scans, fMRI, optogenetics, and other modern technologies. Future progress will continue to depend on improvements in our methods of measurement.Summary1. One way to study brain-behavior relationships is to examine the effects of brain damage. If someone suffers a loss after some kind of brain damage, then that area contributes in some way to that behavior. 912. If stimulation of a brain area increases some behavior, presumably that area contributes to the behavior. Optogenetics is a relatively new method that enables researchers to stimulate a particular type of cell at a particular moment. 923. Researchers try to understand brain-behavior relationships by recording activity in various brain areas during a given behavior. Many methods are available, including EEG, MEG, PET, and fMRI. 934. People who differ with regard to some behavior sometimes also differ with regard to their brain anatomy. MRI is one modern method of imaging a living brain. However, correlations between behavior and anatomy should be evaluated cautiously until they have been replicated. 96Key TermsTerms are defined in the module on the page number indicated. They’re also presented in alphabetical order with definitions in the book’s Subject Index/Glossary, which begins on page 589. Interactive flash cards, audio reviews, and crossword puzzles are among the online resources available to help you learn these terms and the concepts they represent.ablation 91computerized axial tomography (CT or CAT scan) 96electroencephalograph (EEG) 93 lesionevoked potentials or evoked responses 93functional magnetic resonance imaging (fMRI) 94lesion 91magnetic resonance imaging (MRI) 96magnetoencephalograph (MEG) 94optogenetics 92phrenology 96positron-emission tomography (PET) 94stereotaxic instrument 91transcranial magnetic stimulation (TMS) 92Thought QuestionCertain unusual aspects of brain structure were observed in the brain of Albert Einstein (Falk, Lepore, & Noe, 2013). One interpretation is that he was born with certain specialized brain features that encouraged his scientific and intellectual abilities. What is an alternative interpretation?Module 3.3 | End of Module Quiz1. The first demonstration that a brain area controlled a particular aspect of behavior pertained to which type of behavior?A. Criminal activityB. LanguageC. HungerD. Sexual arousal2. Which of the following is a method to inactivate a brain area temporarily?A. Stereotaxic instrumentB. Transcranial magnetic stimulationC. LesionD. Ablation3. What does the optogenetic technique enable researchers to test?A. The evolution of brain anatomyB. The functions of a particular type of neuronC. The relationship between brain anatomy and intelligenceD. How people bind one type of sensation with another4. EEG and MEG are advantageous for measuring which of the following?A. The functions of different neurotransmittersB. The brain areas receiving the greatest amount of blood flow during some activityC. Effects of hormones on behaviorD. Changes in brain activity over very short periods of time5. Which of these is the first step for positron-emission tomography (PET)?A. Inject a radioactive chemical into the blood.B. Insert an electrode into the brain.C. Subject the brain to a strong magnetic field.D. Attach light-sensitive proteins to a virus.6. What is one advantage of fMRI over PET scans?A. The fMRI technique measures activity on a millisecond-by-millisecond basis.B. The fMRI technique does not require inserting an electrode into the head.C. The fMRI technique does not expose the brain to radioactivity.D. The fMRI technique identifies which brain areas are most active at a given moment.7. Comparing MRI and fMRI, which one(s) measure the responses of brain chemicals to a magnetic field? Which one(s) show which brain areas are most active at the moment?A. Only MRI measures responses of brain chemicals to a magnetic field. Both show which brain areas are most active at the moment.B. Only fMRI measures responses of brain chemicals to a magnetic field. Only MRI shows which brain areas are most active at the moment.C. Both measure responses of brain chemicals to a magnetic field. Only fMRI shows which brain areas are most active at the moment.D. Both measure responses of brain chemicals to a magnetic field. Both show which brain areas are most active at the moment.8. Why should we be cautious when interpreting many of the reports linking certain aspects of brain anatomy to behavior?A. Many published studies used inaccurate measures of brain anatomy.B. Many published studies studied people varying widely in their ages.C. Many published studies were based on small samples.D. Many published studies used unethical methods.Answers: 1B, 2B, 3B, 4D, 5A, 6C, 7C, 8C.Suggestion for Further ReadingBurrell, B. (2004). Postcards from the brain museum. New York: Broadway Books. Fascinating history of the attempts to collect brains of successful people and try to relate their brain anatomy to their success.Klawans, H. L. (1988). Toscanini’s fumble and other tales of clinical neurology. Chicago: Contemporary Books. Description of illustrative cases of brain damage and their behavioral consequences. © Cengage