{"id":78,"date":"2013-11-21T18:35:19","date_gmt":"2013-11-21T18:35:19","guid":{"rendered":"http:\/\/opentextbc.ca\/introductiontopsychology\/?post_type=chapter&p=78"},"modified":"2016-11-15T23:35:45","modified_gmt":"2016-11-15T23:35:45","slug":"3-2-our-brains-control-our-thoughts-feelings-and-behavior","status":"publish","type":"chapter","link":"https:\/\/opentextbc.ca\/introductiontopsychology\/chapter\/3-2-our-brains-control-our-thoughts-feelings-and-behavior\/","title":{"raw":"4.2 Our Brains Control Our Thoughts, Feelings, and Behaviour","rendered":"4.2 Our Brains Control Our Thoughts, Feelings, and Behaviour"},"content":{"raw":"
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Learning Objectives<\/h3>\r\n
    \r\n \t
  1. Describe the structures and function of the \u201cold brain\u201d and its influence on behaviour.<\/li>\r\n \t
  2. Explain the structure of the cerebral cortex (its hemispheres and lobes) and the function of each area of the cortex.<\/li>\r\n \t
  3. Define the concepts of brain plasticity, neurogenesis, and brain lateralization.<\/li>\r\n<\/ol>\r\n<\/div>\r\nIf you were someone who understood brain anatomy and were to look at the brain of an animal that you had never seen before, you would nevertheless be able to deduce the likely capacities of the animal. This is because the brains of all animals are very similar in overall form. In each animal the brain is layered, and the basic structures of the brain are similar (see Figure 4.5, \"The Major Structures in the Human Brain\"). The innermost structures of the brain \u2014 the parts nearest the spinal cord \u2014 are the oldest part of the brain, and these areas carry out the same functions they did for our distant ancestors. The \u201cold brain\u201d regulates basic survival functions, such as breathing, moving, resting, and feeding, and creates our experiences of emotion. Mammals, including humans, have developed further brain layers that provide more advanced functions \u2014 for instance, better memory, more sophisticated social interactions, and the ability to experience emotions. Humans have a very large and highly developed outer layer known as the cerebral cortex<\/em> (see Figure 4.6, \"Cerebral Cortex\"), which makes us particularly adept at these processes.\r\n\r\n[caption id=\"attachment_2997\" align=\"aligncenter\" width=\"350\"]\"The<\/a> Figure 4.5 The Major Structures in the Human Brain.[\/caption]\r\n\r\n \r\n\r\n[caption id=\"attachment_72\" align=\"aligncenter\" width=\"400\"]\"""\"<\/a> Figure 4.6 Cerebral Cortex. Humans have a very large and highly developed outer brain layer known as the cerebral cortex. The cortex provides humans with excellent memory, outstanding cognitive skills, and the ability to experience complex emotions.[\/caption]\r\n\r\n \r\n

    The Old Brain: Wired for Survival<\/h2>\r\nThe brain stem\u00a0<\/strong>is the oldest and innermost region of the brain<\/em>. It\u2019s designed to control the most basic functions of life, including breathing, attention, and motor responses (Figure 4.7, \"The Brain Stem and the Thalamus\"). The brain stem begins where the spinal cord enters the skull and forms the medulla<\/strong>, the area of the brain stem that controls heart rate and breathing<\/em>. In many cases the medulla alone is sufficient to maintain life \u2014 animals that have the remainder of their brains above the medulla severed are still able to eat, breathe, and even move. The spherical shape above the medulla is the pons<\/strong>, a structure in the brain stem that helps control the movements of the body, playing a particularly important role in balance and walking<\/em>.\r\n\r\nRunning through the medulla and the pons is a long, narrow network of neurons<\/em> known as the reticular formation<\/strong>. The job of the reticular formation is to filter out some of the stimuli that are coming into the brain from the spinal cord and to relay the remainder of the signals to other areas of the brain. The reticular formation also plays important roles in walking, eating, sexual activity, and sleeping. When electrical stimulation is applied to the reticular formation of an animal, it immediately becomes fully awake, and when the reticular formation is severed from the higher brain regions, the animal falls into a deep coma.\r\n\r\n[caption id=\"attachment_73\" align=\"aligncenter\" width=\"400\"]\"""\"<\/a> Figure 4.7 The Brain Stem and the Thalamus. The brain stem is an extension of the spinal cord, including the medulla, the pons, the thalamus, and the reticular formation.[\/caption]\r\n\r\n \r\n\r\nAbove the brain stem are other parts of the old brain that also are involved in the processing of behaviour and emotions (see Figure 4.8, \"The Limbic System\"). The thalamus<\/strong>\u00a0is the egg-shaped structure above the brain stem that applies still more filtering to the sensory information that is coming up from the spinal cord and through the reticular formation, and it relays some of these remaining signals to the higher brain levels<\/em> (Sherman & Guillery, 2006).\u00a0The thalamus also receives some of the higher brain\u2019s replies, forwarding them to the medulla and the cerebellum. The thalamus is also important in sleep because it shuts off incoming signals from the senses, allowing us to rest.\r\n\r\n[caption id=\"attachment_74\" align=\"aligncenter\" width=\"400\"]\"""\"<\/a> Figure 4.8 The Limbic System. This diagram shows the major parts of the limbic system, as well as the pituitary gland, which is controlled by it.[\/caption]\r\n\r\nThe cerebellum<\/strong>\u00a0(literally, \u201clittle brain\u201d) consists of two wrinkled ovals behind the brain stem. It functions to coordinate voluntary movement<\/em>. People who have damage to the cerebellum have difficulty walking, keeping their balance, and holding their hands steady. Consuming alcohol influences the cerebellum, which is why people who are drunk have more difficulty walking in a straight line. Also, the cerebellum contributes to emotional responses, helps us discriminate between different sounds and textures, and is important in learning (Bower & Parsons, 2003).\r\n\r\nWhereas the primary function of the brain stem is to regulate the most basic aspects of life, including motor functions, the limbic system<\/em> is largely responsible for memory and emotions, including our responses to reward and punishment. The limbic system\u00a0<\/strong>is a brain area, located between the brain stem and the two cerebral hemispheres, that governs emotion and memory<\/em>. It includes the amygdala, the hypothalamus, and the hippocampus<\/em>.\r\n\r\nThe amygdala<\/strong>\u00a0consists of two \u201calmond-shaped\u201d clusters (amygdala comes from the Latin word for \u201calmond\u201d) and is primarily responsible for regulating our perceptions of, and reactions to, aggression and fear<\/em>. The amygdala has connections to other bodily systems related to fear, including the sympathetic nervous system (which we will see later is important in fear responses), facial responses (which perceive and express emotions), the processing of smells, and the release of neurotransmitters related to stress and aggression (Best, 2009).\u00a0In one early study, Kl\u00fcver and Bucy (1939)\u00a0damaged the amygdala of an aggressive rhesus monkey. They found that the once angry animal immediately became passive and no longer responded to fearful situations with aggressive behaviour. Electrical stimulation of the amygdala in other animals also influences aggression. In addition to helping us experience fear, the amygdala also helps us learn from situations that create fear. When we experience events that are dangerous, the amygdala stimulates the brain to remember the details of the situation so that we learn to avoid it in the future (Sigurdsson, Doy\u00e8re, Cain, & LeDoux, 2007).\r\n\r\nLocated just under the thalamus (hence its name), the hypothalamus <\/strong>is a brain structure that contains a number of small areas that perform a variety of functions, including the regulation of hunger and sexual behaviour, as well as linking the nervous system to the endocrine system via the pituitary gland.<\/em> Through its many interactions with other parts of the brain, the hypothalamus helps regulate body temperature, hunger, thirst, and sex, and responds to the satisfaction of these needs by creating feelings of pleasure. Olds and Milner (1954)\u00a0discovered these reward centres accidentally after they had momentarily stimulated the hypothalamus of a rat. The researchers noticed that after being stimulated, the rat continued to move to the exact spot in its cage where the stimulation had occurred, as if it were trying to re-create the circumstances surrounding its original experience. Upon further research into these reward centres, Olds (1958)\u00a0discovered that animals would do almost anything to re-create enjoyable stimulation, including crossing a painful electrified grid to receive it. In one experiment a rat was given the opportunity to electrically stimulate its own hypothalamus by pressing a pedal. The rat enjoyed the experience so much that it pressed the pedal more than 7,000 times per hour until it collapsed from sheer exhaustion.\r\n\r\nThe hippocampus<\/strong> consists of two \u201chorns\u201d that curve back from the amygdala<\/em>. The hippocampus is important in storing information in long-term memory<\/em>. If the hippocampus is damaged, a person cannot build new memories, living instead in a strange world where everything he or she experiences just fades away, even while older memories from the time before the damage are untouched.\r\n

    The Cerebral Cortex Creates Consciousness and Thinking<\/h2>\r\nAll animals have adapted to their environments by developing abilities that help them survive. Some animals have hard shells, others run extremely fast, and some have acute hearing. Human beings do not have any of these particular characteristics, but we do have one big advantage over other animals \u2014 we are very, very smart.\r\n\r\nYou might think that we should be able to determine the intelligence of an animal by looking at the ratio of the animal\u2019s brain weight to the weight of its entire body. But this does not really work. The elephant\u2019s brain is one-thousandth of its weight, but the whale\u2019s brain is only one ten-thousandth of its body weight. On the other hand, although the human brain is one-sixtieth of its body weight, the mouse\u2019s brain represents one-fortieth of its body weight. Despite these comparisons, elephants do not seem 10 times smarter than whales, and humans definitely seem smarter than mice.\r\n\r\nThe key to the advanced intelligence of humans is not found in the size of our brains. What sets humans apart from other animals is our larger cerebral cortex <\/strong>\u2014 the outer bark-like layer of our brain that allows us to so successfully use language, acquire complex skills, create tools, and live in social groups<\/em> (Gibson, 2002).\u00a0In humans, the cerebral cortex is wrinkled and folded, rather than smooth as it is in most other animals. This creates a much greater surface area and size, and allows increased capacities for learning, remembering, and thinking. The folding of the cerebral cortex is referred to as corticalization<\/em>.\r\n\r\nAlthough the cortex is only about one-tenth of an inch thick, it makes up more than 80% of the brain\u2019s weight. The cortex contains about 20 billion nerve cells and 300 trillion synaptic connections (de Courten-Myers, 1999).\u00a0Supporting all these neurons are billions more glial cells<\/strong> (glia), cells that surround and link to the neurons, protecting them, providing them with nutrients, and absorbing unused neurotransmitters<\/em>. The glia come in different forms and have different functions. For instance, the myelin sheath surrounding the axon of many neurons is a type of glial cell. The glia are essential partners of neurons, without which the neurons could not survive or function (Miller, 2005).\r\n\r\nThe cerebral cortex is divided into two hemispheres<\/em>, and each hemisphere is divided into four lobes<\/em>, each separated by folds known as fissures<\/em>. If we look at the cortex starting at the front of the brain and moving over the top (see Figure 4.9, \"The Two Hemispheres\"), we see first the frontal lobe<\/strong> (behind the forehead), which is responsible primarily for thinking, planning, memory, and judgment<\/em>. Following the frontal lobe is the parietal lobe,<\/strong> which extends from the middle to the back of the skull and which is responsible primarily for processing information about touch<\/em>. Then comes the occipital lobe<\/strong> at the very back of the skull, which processes visual information<\/em>. Finally, in front of the occipital lobe (pretty much between the ears) is the temporal lobe<\/strong>, responsible primarily for hearing and language<\/em>.\r\n\r\n[caption id=\"attachment_75\" align=\"aligncenter\" width=\"400\"]\"""\"<\/a> Figure 4.9 The Two Hemispheres. The brain is divided into two hemispheres (left and right), each of which has four lobes (temporal, frontal, occipital, and parietal). Furthermore, there are specific cortical areas that control different processes.[\/caption]\r\n

    Functions of the Cortex<\/h2>\r\nWhen the German physicists Gustav Fritsch and Eduard Hitzig (1870\/2009)\u00a0applied mild electric stimulation to different parts of a dog\u2019s cortex, they discovered that they could make different parts of the dog\u2019s body move. Furthermore, they discovered an important and unexpected principle of brain activity. They found that stimulating the right side of the brain produced movement in the left side of the dog\u2019s body, and vice versa. This finding follows from a general principle about how the brain is structured, called contralateral control, <\/strong>meaning the brain is wired such that in most cases the left hemisphere receives sensations from and controls the right side of the body, and vice versa<\/em>.\r\n\r\n[caption id=\"attachment_76\" align=\"aligncenter\" width=\"400\"]\"""\"<\/a> Figure 4.10 The Sensory Cortex and the Motor Cortex. The portion of the sensory and motor cortex devoted to receiving messages that control specific regions of the body is determined by the amount of fine movement that area is capable of performing. Thus the hand and fingers have as much area in the cerebral cortex as does the entire trunk of the body.[\/caption]\r\n\r\nFritsch and Hitzig also found that the movement that followed the brain stimulation only occurred when they stimulated a specific arch-shaped region that runs across the top of the brain from ear to ear, just at the front of the parietal lobe (see Figure 4.10, \"The Sensory Cortex and the Motor Cortex\"). Fritsch and Hitzig had discovered the motor cortex<\/strong>, the part of the cortex that controls and executes movements of the body by sending signals to the cerebellum and the spinal cord<\/em>. More recent research has mapped the motor cortex even more fully, by providing mild electronic stimulation to different areas of the motor cortex in fully conscious patients while observing their bodily responses (because the brain has no sensory receptors, these patients feel no pain). As you can see in Figure 4.10, \"The Sensory Cortex and the Motor Cortex,\" this research has revealed that the motor cortex is specialized for providing control over the body, in the sense that the parts of the body that require more precise and finer movements, such as the face and the hands, also are allotted the greatest amount of cortical space.\r\n\r\nJust as the motor cortex sends out messages to the specific parts of the body, the somatosensory cortex<\/strong>, an area just behind and parallel to the motor cortex at the back of the frontal lobe, receives information from the skin\u2019s sensory receptors and the movements of different body parts<\/em>. Again, the more sensitive the body region, the more area is dedicated to it in the sensory cortex. Our sensitive lips, for example, occupy a large area in the sensory cortex, as do our fingers and genitals.\r\n\r\nOther areas of the cortex process other types of sensory information. The visual cortex<\/strong>\u00a0is the area located in the occipital lobe (at the very back of the brain) that processes visual information<\/em>. If you were stimulated in the visual cortex, you would see flashes of light or colour, and perhaps you remember having had the experience of \u201cseeing stars\u201d when you were hit in, or fell on, the back of your head. The temporal lobe, located on the lower side of each hemisphere, contains the auditory cortex<\/strong>, which is responsible for hearing and language<\/em>. The temporal lobe also processes some visual information, providing us with the ability to name the objects around us (Martin, 2007).\r\n\r\nThe motor and sensory areas of the cortex account for a relatively small part of the total cortex. The remainder of the cortex is made up of association areas<\/strong>\u00a0in which sensory and motor information is combined and associated with our stored knowledge<\/em>. These association areas are the places in the brain that are responsible for most of the things that make human beings seem human. The association areas are involved in higher mental functions, such as learning, thinking, planning, judging, moral reflecting, figuring, and spatial reasoning.\r\n

    The Brain Is Flexible: Neuroplasticity<\/h2>\r\nThe control of some specific bodily functions, such as movement, vision, and hearing, is performed in specified areas of the cortex, and if these areas are damaged, the individual will likely lose the ability to perform the corresponding function. For instance, if an infant suffers damage to facial recognition areas in the temporal lobe, it is likely that he or she will never be able to recognize faces (Farah, Rabinowitz, Quinn, & Liu, 2000).\u00a0On the other hand, the brain is not divided up in an entirely rigid way. The brain\u2019s neurons have a remarkable capacity to reorganize and extend themselves to carry out particular functions in response to the needs of the organism and to repair damage. As a result, the brain constantly creates new neural communication routes and rewires existing ones. Neuroplasticity<\/strong>\u00a0refers to the brain\u2019s ability to change its structure and function in response to experience or damage<\/em>. Neuroplasticity enables us to learn and remember new things and adjust to new experiences.\r\n\r\nOur brains are the most \u201cplastic\u201d when we are young children, as it is during this time that we learn the most about our environment. On the other hand, neuroplasticity continues to be observed even in adults (Kolb & Fantie, 1989).\u00a0The principles of neuroplasticity help us understand how our brains develop to reflect our experiences. For instance, accomplished musicians have a larger auditory cortex compared with the general population (Bengtsson et al., 2005)\u00a0and also require less neural activity to move their fingers over the keys than do novices (M\u00fcnte, Altenm\u00fcller, & J\u00e4ncke, 2002).\u00a0These observations reflect the changes in the brain that follow our experiences.\r\n\r\nPlasticity is also observed when there is damage to the brain or to parts of the body that are represented in the motor and sensory cortexes. When a tumour in the left hemisphere of the brain impairs language, the right hemisphere will begin to compensate to help the person recover the ability to speak (Thiel et al., 2006).\u00a0And if a person loses a finger, the area of the sensory cortex that previously received information from the missing finger will begin to receive input from adjacent fingers, causing the remaining digits to become more sensitive to touch (Fox, 1984).\r\n\r\nAlthough neurons cannot repair or regenerate themselves as skin or blood vessels can, new evidence suggests that the brain can engage in neurogenesis<\/strong>, the forming of new neurons<\/em> (Van Praag, Zhao, Gage, & Gazzaniga, 2004).\u00a0These new neurons originate deep in the brain and may then migrate to other brain areas, where they form new connections with other neurons (Gould, 2007).\u00a0This leaves open the possibility that someday scientists might be able to \u201crebuild\u201d damaged brains by creating drugs that help grow neurons.\r\n
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    Research Focus: Identifying the Unique Functions of the Left and Right Hemispheres Using Split-Brain Patients<\/h3>\r\nWe have seen that the left hemisphere of the brain primarily senses and controls the motor movements on the right side of the body, and vice versa. This fact provides an interesting way to study brain lateralization <\/strong>\u2014 the idea that the left and the right hemispheres of the brain are specialized to perform different functions<\/em>. Gazzaniga, Bogen, and Sperry (1965)\u00a0studied a patient, known as W. J., who had undergone an operation to relieve severe seizures. In this surgery, the region that normally connects the two halves of the brain and supports communication between the hemispheres<\/em>, known as the corpus callosum<\/strong>, is severed. As a result, the patient essentially becomes a person with two separate brains. Because the left and right hemispheres are separated, each hemisphere develops a mind of its own, with its own sensations, concepts, and motivations (Gazzaniga, 2005).\r\n\r\nIn their research, Gazzaniga and his colleagues tested the ability of W. J. to recognize and respond to objects and written passages that were presented to only the left or to only the right brain hemispheres (see Figure 4.11, \"Visual and Verbal Processing in the Split-Brain Patient\"). The researchers had W. J. look straight ahead and then flashed, for a fraction of a second, a picture of a geometrical shape to the left of where he was looking. By doing so, they ensured that \u2014 because the two hemispheres had been separated \u2014 the image of the shape was experienced only in the right brain hemisphere (remember that sensory input from the left side of the body is sent to the right side of the brain). Gazzaniga and his colleagues found that W. J. was able to identify what he had been shown when he was asked to pick the object from a series of shapes, using his left hand, but that he could not do this when the object was shown in the right visual field. On the other hand, W. J. could easily read written material presented in the right visual field (and thus experienced in the left hemisphere) but not when it was presented in the left visual field.\r\n\r\n[caption id=\"attachment_77\" align=\"aligncenter\" width=\"400\"]\"""\"<\/a> Figure 4.11 Visual and Verbal Processing in the Split-Brain Patient. The information that is presented on the left side of our field of vision is transmitted to the right brain hemisphere, and vice versa. In split-brain patients, the severed corpus callosum does not permit information to be transferred between hemispheres, which allows researchers to learn about the functions of each hemisphere. In the sample on the left, the split-brain patient could not choose which image had been presented because the left hemisphere cannot process visual information. In the sample on the right the patient could not read the passage because the right brain hemisphere cannot process language.[\/caption]\r\n\r\nThis research, and many other studies following it, has demonstrated that the two brain hemispheres specialize in different abilities. In most people the ability to speak, write, and understand language is located in the left hemisphere. This is why W. J. could read passages that were presented on the right side and thus transmitted to the left hemisphere, but could not read passages that were only experienced in the right brain hemisphere. The left hemisphere is also better at math and at judging time and rhythm. It is also superior in coordinating the order of complex movements \u2014 for example, lip movements needed for speech. The right hemisphere, on the other hand, has only very limited verbal abilities, and yet it excels in perceptual skills. The right hemisphere is able to recognize objects, including faces, patterns, and melodies, and it can put a puzzle together or draw a picture. This is why W. J. could pick out the image when he saw it on the left, but not the right, visual field.\r\n\r\nAlthough Gazzaniga\u2019s research demonstrated that the brain is in fact lateralized, such that the two hemispheres specialize in different activities, this does not mean that when people behave in a certain way or perform a certain activity they are only using one hemisphere of their brains at a time. That would be drastically oversimplifying the concept of brain differences. We normally use both hemispheres at the same time, and the difference between the abilities of the two hemispheres is not absolute (Soroker et al., 2005).\r\n\r\n<\/div>\r\n
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    Psychology in Everyday Life: Why Are Some People Left-Handed?<\/h3>\r\nAcross cultures and ethnic groups, about 90% of people are mainly right-handed, whereas only 10% are primarily left-handed (Peters, Reimers, & Manning, 2006).\u00a0This fact is puzzling, in part because the number of left-handers is so low, and in part because other animals, including our closest primate relatives, do not show any type of handedness. The existence of right-handers and left-handers provides an interesting example of the relationship among evolution, biology, and social factors and how the same phenomenon can be understood at different levels of analysis (Harris, 1990; McManus, 2002).\r\n\r\nAt least some handedness is determined by genetics. Ultrasound scans show that nine out of 10 fetuses suck the thumb of their right hand, suggesting that the preference is determined before birth (Hepper, Wells, & Lynch, 2005),\u00a0and the mechanism of transmission has been linked to a gene on the X chromosome (Jones & Martin, 2000).\u00a0It has also been observed that left-handed people are likely to have fewer children, and this may be in part because the mothers of left-handers are more prone to miscarriages and other prenatal problems (McKeever, Cerone, Suter, & Wu, 2000).\r\n\r\nBut culture also plays a role. In the past, left-handed children were forced to write with their right hands in many countries, and this practice continues, particularly in collectivistic cultures, such as\u00a0India and Japan, where left-handedness is viewed negatively as compared with individualistic societies, such as\u00a0Canada and the United States. For example, India has about half as many left-handers as the United States (Ida & Mandal, 2003).\r\n\r\nThere are both advantages and disadvantages to being left-handed in a world where most people are right-handed. One problem for lefties is that the world is designed for right-handers. Automatic teller machines (ATMs), classroom desks, scissors, microscopes, drill presses, and table saws are just some examples of everyday machinery designed with the most important controls on the right side. This may explain in part why left-handers suffer somewhat more accidents than do right-handers (Dutta & Mandal, 2006).\r\n\r\nDespite the potential difficulty living and working in a world designed for right-handers, there seem to be some advantages to being left-handed. Throughout history, a number of prominent artists have been left-handed, including Leonardo da Vinci, Michelangelo, Pablo Picasso, and Max Escher. Because the right hemisphere is superior in imaging and visual abilities, there may be some advantage to using the left hand for drawing or painting (Springer & Deutsch, 1998).\u00a0Left-handed people are also better at envisioning three-dimensional objects, which may explain why there is such a high number of left-handed architects, artists, and chess players in proportion to their numbers (Coren, 1992).\u00a0However, there are also more left-handers among those with reading disabilities, allergies, and migraine headaches (Geschwind & Behan, 2007),\u00a0perhaps due to the fact that a small minority of left-handers owe their handedness to a birth trauma, such as being born prematurely (Betancur, V\u00e9lez, Cabanieu, & le Moal, 1990).\r\n\r\nIn sports in which handedness may matter, such as tennis, boxing, fencing, or judo, left-handers may have an advantage. They play many games against right-handers and learn how to best handle their styles. Right-handers, however, play very few games against left-handers, which may make them more vulnerable. This explains why a disproportionately high number of left-handers are found in sports where direct one-on-one action predominates. In other sports, such as golf, there are fewer left-handed players because the handedness of one player has no effect on the competition.\r\n\r\nThe fact that left-handers excel in some sports suggests the possibility that they may have also had an evolutionary advantage because their ancestors may have been more successful in important skills such as hand-to-hand combat (Bodmer & McKie, 1994).\u00a0At this point, however, this idea remains only a hypothesis, and determinants of human handedness are yet to be fully understood.\r\n\r\n<\/div>\r\n
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    Key Takeaways<\/h3>\r\n