{"id":302,"date":"2021-06-01T19:46:49","date_gmt":"2021-06-01T19:46:49","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/child\/?post_type=chapter&p=302"},"modified":"2024-07-11T20:13:23","modified_gmt":"2024-07-11T20:13:23","slug":"brain-development-2","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/child\/chapter\/brain-development-2\/","title":{"raw":"Brain Development","rendered":"Brain Development"},"content":{"raw":"[caption id=\"attachment_4158\" align=\"alignright\" width=\"590\"]\"Brain Figure 1<\/strong>. Research shows that as early at 4-6 months, infants utilize similar areas of the brain as adults to process information. Image from research article conducted by Ben Deen, Hilary Richardson, Daniel D. Dilks, Atsushi Takahashi, Boris Keil, Lawrence L. Wald, Nancy Kanwisher & Rebecca Saxe.\"Article\u00a0|\u00a0<\/span>OPEN<\/abbr>\u00a0|\u00a0<\/span>Published:\u00a010 January 2017
Organization of high-level visual cortex in human infants\". Image retrieved from\u00a0https:\/\/www.quantamagazine.org\/infant-brains-reveal-how-the-mind-gets-built-20170110\/.[\/caption]\r\n\r\nThe\u00a0nervous system<\/span>\u00a0is composed of two basic cell types: glial cells (also known as glia) and neurons. Glial cells<\/strong> are traditionally thought to play a supportive role to neurons, both physically and metabolically.\u00a0Glial cells<\/span>\u00a0provide scaffolding on which the nervous system is built, help neurons line up closely with each other to allow neuronal communication, provide insulation to neurons, transport nutrients and waste products, and mediate immune responses.\u00a0Neurons<\/span><\/strong>, on the other hand, serve as interconnected information processors that are essential for all of the tasks of the nervous system. This section briefly describes the structure and function of neurons.\r\n\r\nCommunication within the central nervous system (CNS), which consists of the brain and spinal cord, begins with nerve cells called\u00a0neurons<\/strong>. Neurons connect to other neurons via networks of nerve fibers called\u00a0axons<\/strong>\u00a0and\u00a0dendrites<\/strong>. Each neuron typically has a single axon and numerous dendrites that are spread out like branches of a tree (some will say it looks like a hand with fingers). The axon of each neuron reaches toward the dendrites of other neurons at intersections called\u00a0synapses<\/strong>, which are critical communication links within the brain. Axons and dendrites do not touch, instead, electrical impulses in the axons cause the release of chemicals called\u00a0neurotransmitters<\/strong>\u00a0which carry information from the axon of the sending neuron to the dendrites of the receiving neuron.\r\n\r\n\"Parts\r\n

Figure 2.<\/strong> Neuron.<\/p>\r\nhttps:\/\/youtu.be\/6qS83wD29PY?t=9\r\n\r\nVideo 1.\u00a0<\/strong>The Neuron\u00a0<\/em>explains the part of the neuron and the signal transmission of the neurocommunication process.\r\n

Synaptogenesis and Synaptic Pruning<\/h2>\r\nWhile most of the brain\u2019s 100 to 200 billion neurons are present at birth, they are not fully mature.\u00a0Each neural pathway forms thousands of new connections during infancy and toddlerhood.\u00a0Synaptogenesis<\/strong>,\u00a0<\/span>or the formation of connections between neurons<\/em>, continues from the prenatal period forming thousands of new connections during infancy and toddlerhood.\u00a0<\/span>During the next several years,\u00a0dendrites<\/span>,<\/strong>\u00a0or connections between neurons, will undergo a period of\u00a0<\/span>transient exuberance<\/strong>\u00a0or temporary dramatic growth (<\/span>exuberant\u00a0<\/em>because it\u00a0is\u00a0so rapid and\u00a0<\/span>transient<\/em>\u00a0because some of it is\u00a0temporary). <\/span>There is such a proliferation of these dendrites during these early years that by age 2 a single neuron might have thousands of dendrites.\u00a0<\/span>\r\n\r\nAfter this dramatic increase, the neural pathways that are not used will be eliminated through a process called\u00a0<\/span>synaptic<\/strong>\u00a0<\/span>pruning<\/strong>,\u00a0<\/span>where neural connections are reduced, thereby making those that are used much stronger<\/em>.\u00a0<\/span>It is thought that pruning causes the brain to function more efficiently, allowing for mastery of more complex skills (Hutchinson, 2011).\u00a0<\/span>Experience will shape which of these connections are maintained and which of these are lost. Ultimately, about 40 percent of these connections will be lost (Webb, Monk, and Nelson, 2001).<\/span>\u00a0<\/span>Transient exuberance\u00a0occurs during the first few years of life, and pruning continues through childhood and into adolescence in various areas of the brain. This activity is occurring primarily in the\u00a0<\/span>cortex<\/strong>\u00a0or the thin outer covering of the brain involved in voluntary activity and thinking.\u00a0<\/span>\r\n\r\nhttps:\/\/youtu.be\/0S0jKbh6R1I\r\n\r\nVideo 2.\u00a0<\/strong>Synaptic Pruning\u00a0<\/em>explains the reasons for pruning.\r\n

Myelination<\/h2>\r\nAnother significant change occurring in the central nervous system is the development of myelin<\/strong>, a coating of fatty tissues around the axon of the neuron (Carlson, 2014). <\/em>myelin helps insulate the nerve cell and speed the rate of transmission of impulses from one cell to another. This increase enhances the building of neural pathways and improves coordination and control of movement and thought processes.\u00a0During infancy, myelination progresses rapidly, with increasing numbers of axons acquiring myelin sheaths. This corresponds with the development of cognitive and motor skills, including language comprehension, speech acquisition, sensory processing, crawling, and walking.\u00a0Myelination in the motor areas of the brain during early to middle childhood leads to vast improvements in fine and gross motor skills. Myelination continues through adolescence and early adulthood and although largely complete at this time, myelin sheaths can be added in\u00a0grey matter\u00a0regions such as the\u00a0cerebral cortex, throughout life.\r\n\r\nhttps:\/\/youtu.be\/5V7RZwDpmXE?t=8\r\n\r\nVideo 3.\u00a0<\/strong>Myelin\u00a0<\/em>explains the formation and purpose of myelin.\r\n

Neuroplasticity<\/h2>\r\nLastly, neuroplasticity\u00a0<\/strong>refers to the brain's ability to change, both physically and chemically, to enhance its adaptability to environmental change and compensate for injury. Neuroplasticity enables us to learn and remember new things and adjust to new experiences. Both environmental experiences, such as stimulation, and events within a person's body, such as hormones and genes, affect the brain's plasticity. So too does age. Our brains are the most \"plastic\" when we are young children, as it is during this time that we learn the most about our environment. Adult brains demonstrate neuroplasticity, but they are influenced more slowly and less extensively than those of children (Kolb & Whishaw, 2011).\r\n\r\nhttps:\/\/youtu.be\/uVQXZudZd5s\r\n\r\nVideo 4.<\/strong> Long-term Potentiation and Synaptic Plasticity<\/em> explains how learning occurs through synaptic connections and plasticity.\r\n\r\nThe control of some specific bodily functions, such as movement, vision, and hearing, is performed in specified areas of the cortex. 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, likely, he or she will never be able to recognize faces (Farah, Rabinowitz, Quinn, & Liu, 2000). On the other hand, the brain is not divided up in an entirely rigid way. The brain's 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 the damage. As a result, the brain constantly creates new neural communication routes and rewires existing ones.\r\n
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The Amazing Power of Neuroplasticity<\/h3>\r\nVideo 5.<\/strong> The Story of Jody<\/em> is a case study about a young girl that had the right hemisphere of her brain removed as a treatment for severe seizures. Due to neuroplasticity, Jody was able to recover from the damage caused by the removal of so much of her cerebrum.\r\n\r\nhttps:\/\/youtu.be\/VaDlLD97CLM\r\n\r\n<\/div>\r\n

Brain Structures<\/h2>\r\nAt birth, the brain is about 25 percent of its adult weight, and by age two, it is at 75 percent of its adult weight. Most of the neural activity is occurring in the cortex <\/strong>or the thin outer covering of the brain involved in voluntary activity and thinking.\u00a0The cortex is divided into two hemispheres, and each hemisphere is divided into four lobes, each separated by folds known as fissures. If we look at the cortex starting at the front of the brain and moving over the top, we see first the frontal lobe <\/strong>(behind the forehead),\u00a0which is responsible primarily for thinking, planning, memory, and judgment. 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. Next is the occipital lobe<\/strong>, at the very back of the skull, which\u00a0processes visual information. Finally, in front of the occipital lobe, between the ears, is the temporal lobe<\/strong>, which is\u00a0responsible for hearing and\u00a0language.\r\n\r\n\"\"\r\n

Figure 3.<\/strong> Lobes of the brain.<\/p>\r\nAlthough the brain grows rapidly during infancy, specific brain regions do not mature at the same rate. Primary motor areas develop earlier than primary sensory areas, and the prefrontal cortex, which is located behind the forehead, is the least developed. As the prefrontal cortex matures, the child is increasingly able to regulate or control emotions, plan activities, strategize, and have better judgment. This maturation is not fully accomplished in infancy and toddlerhood but continues throughout childhood, adolescence, and even into adulthood.\r\n\r\nDuring adolescence, some of the most developmentally significant changes in the brain occur in the\u00a0prefrontal cortex<\/strong>, which is involved in\u00a0decision making\u00a0and cognitive control, as well as other higher cognitive functions.\u00a0During adolescence,\u00a0myelination<\/strong>\u00a0and\u00a0synaptic pruning<\/strong>\u00a0in the prefrontal cortex increases, improving the efficiency of information processing, and neural connections between the prefrontal cortex and other regions of the brain are strengthened.\u00a0However, this growth takes time, and the growth is uneven.\r\n\r\nhttps:\/\/youtu.be\/LQ4DlE1Xyd4?t=12\r\n\r\nVideo 6.\u00a0<\/strong>Lobes and Landmarks of the Brain Surface\u00a0<\/em>identifies the lobes and some of the major cortexes of the brain.\r\n

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The Prefrontal Cortex<\/h3>\r\n<\/div>\r\nThe prefrontal cortex, the part of the frontal lobes lying just behind the forehead, is often referred to as the \u201cCEO of the brain,\u201d the cognitive control center. This brain region is responsible for cognitive analysis, abstract thought, the moderation of \u201ccorrect\u201d behavior in social situations, the capacity to exercise good judgment, self-regulation and future orientation The prefrontal cortex takes in information from all of the senses and orchestrates thoughts and actions to achieve specific goals (Casey, Jones, & Hare, 2008; Walsh, 2004). Around 11 years of age, this region of the brain begins an extended process of pruning and myelination and is not complete until near the age of 25. This is one of the last regions of the brain to reach maturation. This delay may help to explain why some adolescents act the way they do. The so-called \u201cexecutive functions\u201d of the human prefrontal cortex include:\r\n
    \r\n \t
  • Focusing attention<\/li>\r\n \t
  • Organizing thoughts and problem-solving<\/li>\r\n \t
  • Foreseeing and weighing possible consequences of behavior<\/li>\r\n \t
  • Considering the future and making predictions<\/li>\r\n \t
  • Forming strategies and planning<\/li>\r\n \t
  • Ability to balance short-term rewards with long term goals<\/li>\r\n \t
  • Shifting\/adjusting behavior when situations change<\/li>\r\n \t
  • Impulse control and delaying gratification<\/li>\r\n \t
  • Modulation of intense emotions<\/li>\r\n \t
  • Inhibiting inappropriate behavior and initiating appropriate behavior<\/li>\r\n \t
  • Simultaneously considering multiple streams of information when faced with complex and challenging information<\/li>\r\n<\/ul>\r\n\"\"\r\n

    Figure 4.<\/strong> Brain development continues into the early 20s. The development of the frontal lobe, in particular, is important during this stage.<\/p>\r\nThe difference in timing of the development of the limbic system and prefrontal cortex contributes to more risk-taking during adolescence because adolescents are motivated to seek thrills that sometimes come from risky behavior, such as reckless driving, smoking, or drinking, and have not yet developed the cognitive control to resist impulses or focus equally on the potential risks (Steinberg, 2008).\u00a0One of the world\u2019s leading experts on adolescent development, Laurence Steinberg, likens this to engaging a powerful engine before the braking system is in place. The result is that adolescents are more prone to risky behaviors than are children or adults.\r\n

    Lateralization<\/h3>\r\nLateralization <\/strong>is the process in which different functions become localized primarily on one side of the brain. For example, in most adults, the left hemisphere is more active than the right during language production, while the reverse pattern is observed during tasks involving visuospatial abilities (Springer & Deutsch, 1993). This process develops over time, however, structural asymmetries between the hemispheres have been reported even in fetuses (Chi, Dooling, & Gilles, 1997; Kasprian et al., 2011) and infants (Dubois et al., 2009).\r\n

    Growth in the Hemispheres and Corpus Callosum<\/strong><\/h3>\r\nBetween ages 3 and 6, the left hemisphere of the brain grows dramatically. This side of the brain or hemisphere is typically involved in language skills. The right hemisphere continues to grow throughout early childhood and is involved in tasks that require spatial skills, such as recognizing shapes and patterns. The Corpus Callosum, a dense band of fibers that connects the two hemispheres of the brain,\u00a0contains approximately 200 million nerve fibers that connect the hemispheres (Kolb & Whishaw, 2011).\r\n\r\nThe corpus callosum is located a couple of inches below the longitudinal fissure, which runs the length of the brain and separates the two cerebral hemispheres (Garrett, 2015). Because the two hemispheres carry out different functions, they communicate with each other and integrate their activities through the corpus callosum. Additionally, because incoming information is directed toward one hemisphere, such as visual information from the left eye being directed to the right hemisphere, the corpus callosum shares this information with the other hemisphere.\r\n\r\nThe corpus callosum undergoes a growth spurt between ages 3 and 6, and this results in improved coordination between right and left hemisphere tasks. For example, in comparison to other individuals, children younger than 6 demonstrate difficulty coordinating an Etch A Sketch toy because their corpus callosum is not developed enough to integrate the movements of both hands (Kalat, 2016).\r\n\r\n\"\"\r\n

    Figure 5.<\/strong>\u00a0Corpus callosum.<\/p>\r\n\r\n

    The Limbic System<\/h3>\r\nThe\u00a0limbic system<\/strong>\u00a0develops years ahead of the prefrontal cortex. Development in the limbic system plays an important role in determining rewards and punishments and processing emotional experience and social information. Pubertal hormones target the\u00a0amygdala<\/strong>\u00a0directly, and powerful sensations become compelling (Romeo, 2013).\u00a0Brain scans confirm that cognitive control, revealed by fMRI studies, is not fully developed until adulthood because the prefrontal cortex is limited in connections and engagement (Hartley & Somerville, 2015).\u00a0Recall that this area is responsible for judgment, impulse control, and planning, and it is still maturing into early adulthood (Casey, Tottenham, Liston, & Durston, 2005).\r\n\r\n\"\"\r\n

    Figure 6.<\/strong>\u00a0The limbic system.<\/p>\r\nAdditionally, changes in both the levels of the neurotransmitters\u00a0dopamine<\/strong>\u00a0and\u00a0serotonin<\/strong>\u00a0in the limbic system make adolescents more emotional and more responsive to rewards and stress. Dopamine\u00a0is a neurotransmitter in the brain associated with pleasure and attuning to the environment during decision-making. During adolescence, dopamine levels in the\u00a0limbic system\u00a0increase, and the input of dopamine to the prefrontal cortex increases.\u00a0The increased dopamine activity in adolescence may have implications for adolescent risk-taking and vulnerability to boredom.\u00a0Serotonin is\u00a0involved in the regulation of mood and behavior. It affects the brain in a different way. Known as the \u201ccalming chemical,\u201d serotonin eases tension and stress. Serotonin also puts a brake on the excitement and sometimes recklessness that dopamine can produce. If there is a defect in the serotonin processing in the brain, impulsive or violent behavior can result.\r\n

    Brain Region Integration<\/h3>\r\nMRI studies of the brain show that developmental processes tend to occur in the brain in a back-to-front pattern, explaining why the prefrontal cortex develops last. These studies have also found that teens have less white matter (myelin) in the frontal lobes of their brains when compared to adults, but this amount increases as the teen ages. With more myelin comes the growth of important brain connections, allowing for a better flow of information between brain regions. MRI research has also revealed that during adolescence, white matter increases in the corpus callosum, the bundle of nerve fibers connecting the right and left hemispheres of the brain. This allows for enhanced communication between the hemispheres and enables a full array of analytic and creative strategies to be brought to bear in responding to the complex dilemmas that may arise in a young person\u2019s life (Giedd, 2004).\r\n\r\nIn sum, the adolescent years are a time of intense brain changes. Interestingly, two of the primary brain functions develop at different rates. Brain research indicates that the part of the brain that perceives rewards from risk, the limbic system, kicks into high gear in early adolescence. The part of the brain that controls impulses and engages in longer-term perspective, the frontal lobes, mature\u00a0later. This may explain why teens in mid-adolescence take more risks than older teens.\u00a0As the frontal lobes become more developed, two things happen. First, self-control develops as teens are better able to assess cause and effect. Second, more areas of the brain become involved in processing emotions, and teens become better at accurately interpreting others\u2019 emotions.\r\n\r\nhttps:\/\/youtu.be\/5Fa8U6BkhNo\r\n\r\nVideo 7.<\/strong>\u00a0Brain Changes during Adolescence <\/em>describes some of the physical changes that occur during adolescence.\r\n
    \r\n

    The Teen Brain: 6 Things to Know from the National Institute of Mental Health<\/h3>\r\n
    Your brain does not keep getting bigger as you get older<\/span><\/div>\r\nFor girls, the brain reaches its largest physical size around 11 years old and for boys, the brain reaches its largest physical size around age 14. Of course, this difference in age does not mean either boys or girls are smarter than one another!\r\n
    \r\n

    But that doesn\u2019t mean your brain is done maturing<\/h4>\r\n<\/div>\r\nFor both boys and girls, although your brain may be as large as it will ever be, your brain doesn\u2019t finish developing and maturing until your mid- to late-20s. The front part of the brain, called the prefrontal cortex, is one of the last brain regions to mature. It is the area responsible for planning, prioritizing, and controlling impulses.\r\n
    \r\n

    The teen brain is ready to learn and adapt<\/h4>\r\n<\/div>\r\nIn a digital world that is constantly changing, the adolescent brain is well prepared to adapt to new technology\u2014and is shaped in return by experience.\r\n
    \r\n

    Many mental disorders appear during adolescence<\/h4>\r\n<\/div>\r\nAll the big changes the brain is experiencing may explain why adolescence is the time when many mental disorders\u2014such as schizophrenia, anxiety, depression, bipolar disorder, and eating disorders\u2014emerge.\r\n
    \r\n

    The teen brain is resilient<\/h4>\r\n<\/div>\r\nAlthough adolescence is a vulnerable time for the brain and for teenagers in general, most teens go on to become healthy adults. Some changes in the brain during this important phase of development actually may help protect against long-term mental disorders.\r\n
    \r\n

    Teens need more sleep than children and adults<\/h4>\r\n<\/div>\r\nAlthough it may seem like teens are lazy, science shows that melatonin levels (or the \u201csleep hormone\u201d levels) in the blood naturally rise later at night and fall later in the morning than in most children and adults. This may explain why many teens stay up late and struggle with getting up in the morning. Teens should get about 9-10 hours of sleep a night, but most teens don\u2019t get enough sleep. A lack of sleep makes paying attention hard, increases impulsivity, and may also increase irritability and depression.\r\n","rendered":"
    \"Brain<\/p>\n

    Figure 1<\/strong>. Research shows that as early at 4-6 months, infants utilize similar areas of the brain as adults to process information. Image from research article conducted by Ben Deen, Hilary Richardson, Daniel D. Dilks, Atsushi Takahashi, Boris Keil, Lawrence L. Wald, Nancy Kanwisher & Rebecca Saxe.”Article\u00a0|\u00a0<\/span>OPEN<\/abbr>\u00a0|\u00a0<\/span>Published:\u00a010 January 2017
    Organization of high-level visual cortex in human infants”. Image retrieved from\u00a0https:\/\/www.quantamagazine.org\/infant-brains-reveal-how-the-mind-gets-built-20170110\/.<\/p>\n<\/div>\n

    The\u00a0nervous system<\/span>\u00a0is composed of two basic cell types: glial cells (also known as glia) and neurons. Glial cells<\/strong> are traditionally thought to play a supportive role to neurons, both physically and metabolically.\u00a0Glial cells<\/span>\u00a0provide scaffolding on which the nervous system is built, help neurons line up closely with each other to allow neuronal communication, provide insulation to neurons, transport nutrients and waste products, and mediate immune responses.\u00a0Neurons<\/span><\/strong>, on the other hand, serve as interconnected information processors that are essential for all of the tasks of the nervous system. This section briefly describes the structure and function of neurons.<\/p>\n

    Communication within the central nervous system (CNS), which consists of the brain and spinal cord, begins with nerve cells called\u00a0neurons<\/strong>. Neurons connect to other neurons via networks of nerve fibers called\u00a0axons<\/strong>\u00a0and\u00a0dendrites<\/strong>. Each neuron typically has a single axon and numerous dendrites that are spread out like branches of a tree (some will say it looks like a hand with fingers). The axon of each neuron reaches toward the dendrites of other neurons at intersections called\u00a0synapses<\/strong>, which are critical communication links within the brain. Axons and dendrites do not touch, instead, electrical impulses in the axons cause the release of chemicals called\u00a0neurotransmitters<\/strong>\u00a0which carry information from the axon of the sending neuron to the dendrites of the receiving neuron.<\/p>\n

    \"Parts<\/p>\n

    Figure 2.<\/strong> Neuron.<\/p>\n