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the dana sourcebook of brain science resources for teachers and students fourth edition david balog editor new york · washington d.c.

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from the dana foundation william safire chairman edward f rover president edward bleier wallace l cook charles a dana iii steven e hyman m.d ann mclaughlin korologos lasalle d leffall jr m.d hildegarde e mahoney donald b marron l guy palmer ii herbert j siegel the dana foundation 745 fifth avenue suite 900 new york ny 10151 900 15th street nw washington dc 20005 this publication is provided by the dana foundation free to participating schools the dana foundation is a private philanthropic organization with particular interests in science health and education please note additional copies or classroom sets may be ordered through www.dana.org also access the online edition at www.dana.org isbn 10 1-932594-19-1 isbn 13 978-1-932594-19-5 library of congress cataloging-in-publication data the dana sourcebook of brain science resources for secondary and post-secondary teachers and students david balog editor 4th ed p cm includes bibliographical references and index isbn 1-932594-19-1 alk paper 1 brain i balog david 1957qp376.d36 2006 612.8 2 dc22 2006007158 copyright 2006 dana press a dana press publication jane nevins editor in chief

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contents preface 5 6 8 scientific lives 1 revealing the workings the wonder of the human brain 2 genes and the brain 19 23 26 27 28 31 3 stem cells and brain research 4 advances in brain research the role of nature innate gifts and hereditary factors new frontiers in neural imaging listening to learn 29 32 34 neuroimmunology a connection with the brain my brain made me do it out of the blue 33 35 37 38 39 behind the scenes in the adolescent brain defining stroke or brain attack what exactly are antidepressants the science of attracting axons the developing nervous system vision the final key to spinal cord regeneration allostatic load scenario 4 too little is as bad as too much research and future treatments for alzheimer s disease how your brain forms memories the power of emotions use it or lose it imagine a world 45 47 44 42 41 40

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5 suggested activities 56 6 important books on the brain an annotated bibliography of fiction and non-fiction 67 83 7 tracing shakespeare s insights through modern brain science a note on sources of information on the brain a glossary of key brain science terms maps of the brain 110 116 127 99 93 resources on the web acknowledgments index 129

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preface lynn wecker ph.d scientific consultant the dana sourcebook of brain science fourth edition b ecause of new and improved brain research techniques neuroscientists neurologists psychiatrists and neurosurgeons are learning more every day about what has been called the most complex structure in the known universe the human brain we are steadily gaining understanding about how the brain functions thinks feels imagines and remembers much of who we are and how we live depends on maintaining a healthy active brain modern medicine is bringing new hope in the form of treatments for those whose brain has been compromised by disease or trauma the dana sourcebook of brain science resources for teachers and students is designed to introduce readers to brain science its history our current understanding of this complex system and future directions we are confident that you will find this book our fourth edition both informative and useful 5

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scientific lives part one a life of research advancing our knowledge of how the brain works editor s note one way to study the brain is to become a researcher conducting experiments analyzing data publishing results and teaching a leading scientist and researcher on depression and mental health huda akil ph.d is gardner quarton distinguished university professor of neuroscience and psychiatry and co-director of the mental health research institute at the university of michigan dr akil is former president of the society for neuroscience the world s largest organization of scientists devoted to the study of the brain huda akil ph.d a leader in emotions research and an advocate for neuroscience education dr huda akil is a national advocate for the inclusion of neuroscience education in schools she knows firsthand from teaching school-age children and adolescents that the brain fascinates them young people are intensely huda akil ph.d interested in how their minds function and change as they develop first-graders have asked me `what happens in our brains when we dream `where do the memories go when we forget older students have profound questions about emotions psychoactive drugs brain-related illnesses consciousness in short all the questions that occupy neuroscientists sometimes these questions are intellectual or philosophical but often they are intensely personal after some of my high-school 6 talks students have asked me about friends who had died of suicide family members suffering from alzheimer s classmates addicted to drugs and other topics dr akil describes her own love of science as a great gift she was about twelve and living in her native city of damascus syria when the french nun who ran the library suggested that she read a book on the life of marie curie who pioneered the therapeutic uses of radium early in the 20th century i was fascinated by both what she discovered and the fact that a young woman from a remote place could become so successful i began to read everything i could on scientific discovery for young women today dr akil says there are excellent opportunities for pursuing scientific careers they typically demonstrate a great deal of talent and dedication i do feel however that the career paths of men and women scientists are somewhat different in that women peak a bit later possibly because of the demands of child bearing and rearing i hope that young women keep this in mind as they assess their careers and that institutions bear it in mind in their evaluations and willingness to support women in her study of depression dr akil thinks many genes likely interact to produce a vulnerability to an illness and none of these genes need be abnormal rather combinations of variants of genes can result in different likelihoods of being prone or resistant to a given disorder and of course the impact of the environment is critical says dr akil understanding emotionality is extremely challenging it embodies the problems and the excitement of neuroscience j

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scientific lives part two treating patients with brain diseases and disorders editor s note in addition to conducting research and teaching brain scientists can also be hands-on doctors and surgeons benjamin s carson sr m.d one of the world s leading neurosurgeons is director of pediatric neurosurgery at johns hopkins medical institutions he is professor of neurosurgery oncology plastic surgery and pediatrics at the johns hopkins university school of medicine benjamin s carson sr m.d a brain surgeon talks about second chances not long ago doctors whose practices focused on the brain had few tools to intervene significantly in their patients lives that has changed quickly brain doctors are now aggressively treating patients for stroke benjamin carson m.d seizures acute trauma psychoses addiction and even some neurodegenerative disorders one of these pioneers is dr benjamin carson during his career he has gained international distinction for successful delicate high-risk surgeries such as hemispherectomies removing one side of the brain to treat those suffering from otherwise untreatable severe multiple seizures dr carson speaks often to young students and emphasizes his own transition from poor inner-city kid in detroit with failing grades to one of the most prestigious positions at one of the world s most renowned medical institutions is it ever too late if you miss the boat the first time around well i have to tell you when i was a youngster many people would have said it was too late for me no one certainly would have thought that i was going to grow up to be a physician his mother sonya was determined to help and she ordered ben and his brother curtis to read two books each week which she with only a third-grade education pretended to review once my mother made us start reading what a tremendous change took place says dr carson becoming a successful student didn t protect him from racist treatment nor from his rage against it in high school a teacher scolded ben s white classmates for letting a black student win the outstanding-achievement award then one day ben tried to stab a student who had changed the station on a radio the student had a large metal belt buckle and the knife blade struck it and broke frightened by his anger ben ran home and prayed for hours devoutly religious like his mother he says he has not lost his temper since dr carson went on to win a college scholarship later i bombed out of my first set of comprehensive medical exams the counselor suggested that there were a lot of things i could do besides medicine dr carson at that point thought back to his mother s earlier encouragement to read i decided to concentrate on reading which then made medical school a snap taking advantage of how we learn is incredibly important dr carson believes in today s students he is president and co-founder of the carson scholars fund which recognizes young people of all backgrounds for exceptional academic and humanitarian accomplishments he says we need to start putting our resources where it counts and honoring our academic superstars j 7

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chapter 1 revealing the workings the wonder of the human brain do each of the following in succession this is not a test 1 visualize a place you d like to be maybe it s lounging on a sunny summer day at the beach maybe it s in your living room watching a favorite movie create the image of that place in your mind and hold it for a minute or two listen to the sounds in the room around you really listen what do you hear low voices in conversation muffled laughter in the hall phones and computers ringing and beeping see how many sounds you can differentiate silently tap your fingers on the desk one tap one finger at a time in succession then reverse the order of tapping then tap each finger twice in succession then in reverse then three times starting at 100 count backward by 7s remember some event from your past the first time you rode a bike all by yourself your grandmother baking your favorite cookies the first time you kissed someone other than a relative put yourself back in that place and recall everything you can about it who was there with you what were you wearing what emotions were you feeling now pinch yourself pick a tender spot on the inside of your elbow and pinch the skin just hard enough to feel pain 2 3 4 5 6 8

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revealing the workings the wonder of the human brain i n performing these six tasks you ve just activated a good portion of your brain even something as simple as tapping your fingers in succession requires a phenomenal act of coordination among millions of nerve cells throughout the brain all acting together in perfect timing to produce the signals that command your fingers to move if you had been lying inside a pet or fmri scanner tools of modern neuroscience that enable scientists to take images of the living brain as it works the scans would the brain weighing approximately three pounds makes us distinctively human it encases 100 billion or more nerve cells and can send signals to thousands of show distinct areas of your brain other cells at a rate of about 200 miles an hour lighting up as you did each task tapping your fingers in succession would activate groups of neurons in at least four recalling a memory from your past will likely distinct areas of the brain the prefrontal cortex activate the hippocampus an inner-brain structure where your brain makes the conscious decision to involved in memory as well as other areas of the do the task the premotor cortex where you formubrain that correspond to the type of memory for late the instructions for doing the task the motor example remembering the first time you rode a cortex a sort of relay station that sends those bike a motor task will light up the motor area of instructions on to the arm and hand muscles that the brain recalling the smell of grandma s cookmove the fingers and the cerebellum which superies would activate the olfactory center vises the whole process and adjusts your actions lastly when you pinched yourself pain as necessary in response to external cues such as receptors in the nerves of the skin sent signals where your hand is in relation to the desk all of back to the brain to alert it to the location and this takes place in a mere fraction of a second intensity of the pain and to initiate corrective not such a simple task after all from the action if necessary i.e stop pinching if the brain s perspective pain was intense the brain might release endortask number one visual imagery lights up phins natural hormones that block the transmisthe visual cortex in the back of the brain as well as sion of pain signals narcotic drugs such as pathways leading to it from the eyes along the morphine imitate the action of these natural optic nerve differentiating individual sounds endorphins to fight pain around you activates the auditory cortex and associated areas tapping your fingers stimulates your the most complex achievement motor cortex which is involved in movement and of nature muscle coordination counting backward by 7s is you ve just taken a brief tour of your brain it has a complex cognitive task and it calls upon the taken scientists hundreds of years to figure out brain s center for higher thoughts in the prethe bits of information you ve just learned in a frontal cortex few minutes if that seems like a long time for a note terms in italics are defined in a glossary of key brain science terms beginning on page 99 9

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the dana sourcebook of brain science little bit of information consider the complexity of the problem the human brain is as neuroscientist joseph ledoux ph.d says in the emotional brain the most sophisticated machine imaginable or unimaginable it is composed of more than 100 billion nerve cells each of which forms as many as 10,000 connections with other neurons a typical brain weighs about three pounds just two percent of the total body weight of a 150pound person but the brain uses between 20 percent and 25 percent of the body s oxygen and a substantial amount of the calories we consume in the form of the blood sugar glucose the brain is also a nonstop factory of neurotransmitters that are critical to every thought and feeling we experience about half of the 30,000 or so genes in the human genome are committed to building and operating the central nervous system the brain and spinal cord tem result in more hospitalizations than any other disease group including heart disease and cancer brain damage by stroke they report is one of the three greatest medical sources of death depression causes the greatest disability for adults under the age of 45 and suicides continue to outnumber homicides by almost two to one the aging of our population makes alzheimer s and other neurodegenerative diseases an increasing public health concern at the beginning of the lifespan autism and related disorders have now been estimated at 1 in 166 births roughly a tenfold increase in the past decade evolution of the brain the modern human brain is the product of millennia of evolutionary tinkering says dr ledoux to figure out how it works we need to pick the brain apart in the hope that we will see what evo about half of the 30,000 or so genes in the human genome are committed to building the central nervous system the brain and spinal cord in the process of deciphering the genetic code that is written in our dna learning the blueprint of our bodies is also likely to pave the way for a better understanding of the brain-based disorders and diseases that plague mankind and open new avenues for treating these disorders this is an undertaking with enormous implications because more than 60 million americans are afflicted with a brain disorder conditions that range from learning disabilities to depression to traumatic brain injury that s nearly one in five of us look around you if there are 25 students in your class statistically 5 of you will be personally affected every one of us will personally know or care for someone who is affected by a brain disease or disorder today leading brain researchers report that the more than 1,000 disorders of the nervous sys10 lution was up to when it put the device together for centuries picking the brain apart was literally how scientists learned how the brain worked actually they usually picked apart the brains of other animals for clues as to how the human brain worked as it turns out the human brain is remarkably similar to the brains of other mammals from rats right up to our closest cousins in the evolutionary tree the great apes in evolutionary terms most of the structures in our brain are in fact primitive that is they have existed in much the same form for eons these include the parts of the brain that control functions basic to survival such as breathing heart rate and digestion such functions are centralized in the brain stem located in the base of the brain where the spinal cord meets the brain continued on page 12

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revealing the workings the wonder of the human brain brain imaging a closer look computer technology has opened a window on the living brain before the early 1970s only neurosurgeons had seen a living human brain rapid advances in computer-generated imaging have allowed brain scientists and doctors to go inside the head and examine the structure and function of the brain in the living patient advances in the next few decades are expected to allow scientists to investigate how brain circuits work how one part of the brain modifies the functions of other parts and how these circuits adapt to new situations or damage to existing circuits j measuring metabolism positron emission tomography or pet allows scientists to recreate images of the living functioning human brain these images demonstrate that certain areas of the brain activate as the brain performs specific language tasks magnetic resonance imaging or mri employs powerful magnets to produce sharp anatomical three-dimensional images of the brain and all other parts of the body in just one example of their use neurosurgeons employ mris of the brain to plan surgery for epilepsy patients expanding on conventional mri by detecting variations in the response of hydrogen atoms when oxygen is present in the blood functional magnetic resonance imaging or fmri creates images that show which areas of the brain are working during specific tasks behaviors or thoughts here image b represents the brain areas at work in a sighted person reading a one-syllable word in braille in image c a visually-disabled person reads the same word in braille and shows brain activity in additional areas suggesting that the brain of the visually impaired person has reorganized its sensory pathways the graphs represented by d and e plot the data of the experiment 11

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the dana sourcebook of brain science continued from p 10 left h.m with a severe memory disorder in which he could learn but not retain new information he couldn t recall having met someone moments what makes human brains so special after that person had left the room by observing clearly humans have so-called specialized funch.m s behavior and correlating it to the missing tions that rats or even great apes do not so what parts of his brain scientists were able to learn makes humans so special the key seems to lie in which parts of the brain were responsible for certhe prefrontal cortex the forward-most section of tain behaviors his case single-handedly shaped the cerebral cortex which is the brain s outermost the course of memory research for decades layer of gray matter this is the brain s command while h.m and legions of other brain-injury and control center where higher cognitive funcsurvivors spurred important advances in undertions are centralized including the abilities for standing the brain for much of scientific history thinking reasoning believing planning and the brain was a black box a mystery so profound social consciousness things that set us apart from it was long considered to be the realm of philosoother animals the prefrontal cortex is more highphy or religion not science the 15th-century ly developed in humans than in any other priphilosopher rené descartes promoted the idea mate and it may not even exist in other that the mind was separate from the brain or mammals this is an area of continuing scientific body an idea that has stubbornly persisted even exploration in this age of modern medicine argues antonio in addition to examining the brains of other damasio m.d ph.d in descartes error indeed animals scientists have made great strides in medical science has only recently begun to recogunderstanding brain function by observing people nize the links between psychological phenomena who have suffered trauma to the brain some of and physical health or the power of the mind to the most important breakthroughs in the biology influence healing in the body of memory systems in the brain for example came the drive to understand the brain s mysterfrom the study of a young man known as h.m ies picked up speed as scientific methods who underwent a radical surgery in which large advanced as the 19th century ended two sciensections of his temporal lobes were removed to contists an italian physician named camillo golgi trol epileptic seizures the surgery worked but it and a spanish anatomist named santiago ramón y cajal forever changed our understanding of the brain and shared the 1906 nobel prize in physiology or medicine for their work while golgi s theories about brain function were later disproved his techniques in which he stained brain tissue with silver nitrate and other substances to reveal its inner structure are still used today just as important golgi opened scientists eyes to the true complexity of the human brain notes bruce s mcewen ph.d a scientists study the brains of other mammals to understand structures that bear remarkable similarity to the human brain particularly those located in leading neuroscientist at rockefeller the brain stem university golgi they say was the 12

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revealing the workings the wonder of the human brain first to see the brain as a network of connected cells even though he was wrong about how the cells were connected his work spurred others including cajal to look at the brain differently cajal advanced what later became known as the neuron theory which proposed that nerve cells were not structurally connected as golgi thought but were separate cells connected in some other unknown way advantage of the fact that nerve cells metabolize the sugar glucose to derive the energy needed to perform their roles in brain function by measuring changes in glucose uptake by nerve cells pet enables scientists to determine which areas of the brain are activated during specific tasks such as the finger-tapping exercise discussed earlier the introduction of pet got people thinking about other strategies for mapping the brain and mri magnetic resonance imaging soon followed rather than measuring how much glucose cells metabolize mri uses intensely powerful magnets and radio-wave pulses to capture images of the brain s structure standard mri and function fmri standard mri relies on the fact that molecules within cells when placed in the strong magnetic field of an mri scanner line up in a certain fashion much like the needle on a compass lines up with the earth s magnetic field when pulses of radio waves are applied to tissues with such alignment the nuclei of individual molecules resonate the signals back in varying patterns that correspond to the chemical makeup of each area of tissue being studied scientists can then reconstruct anatomical images based on the patterns of resonance in recent years sophisticated computer techniques have enabled brain imagers to take mri to the next level creating images that depict brain function in addition to anatomical structure using a standard mri scanner scientists can track which areas of the brain are active when a specific region of the brain is active neurons in that area use more oxygen fmri takes advantage of the different magnetic properties of oxygenated and deoxygenated blood blood that has not been used by brain cells and blood that has been used the relative concentrations of oxygenated and deoxygenated blood are measured and charted onto standard mr images of the brain to show which areas are working chemical electrical pulses spark brain cell communication over the next couple of decades scientists began to tease out the details of nerve cell communication they learned that the connections cajal had hypothesized to be the underpinnings of all human behavior were actually formed through a complex chemical signaling process in this relay race of life they learned one cell squirts out a neurotransmitter a chemical messenger that crosses the synaptic gap between nerve cells and latches onto receptors on the surface of a neighboring cell it wasn t long before dozens of neurotransmitters were discovered and systematically analyzed to determine their roles in cognition behavior and disease processes by the 1970s it had become clear that brain function was the result of a complex interplay of chemical transmitters jolted into action by electrical impulses the pulses were generated by ion channels within the neuron which acted like the starting gun for the relay race of interneuronal communication today scientists continue to elaborate the processes of cell-to-cell communication in exquisite detail and a new arm of science has evolved that is now exploring the events that occur beyond the receptor within the postsynaptic cell the 1970s and 1980s were important decades for brain science the development of pet positron emission tomography during this period enabled scientists to capture anatomical images of the living functioning human brain and to begin to inventory the neurotransmitters involved in various behaviors or brain disorders pet takes brain function the sum of many parts imaging techniques such as pet and fmri have revolutionized the field of brain science enabling 13

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the dana sourcebook of brain science changes that can lead to mental deterioration in later life now new evidence suggests the brain may be even more plastic than previously thought turning one of the oldest tenets of neuroscience on its head scientists recently discovered that nerve cells can regenerate making the idea of brain repair following trauma or disease thinkable revealed at the end of the 20th century this scientific breakthrough is sure to influence brain science for at least the next century here is an image of a single neuron taken from a rat brain isolated in culture scientists estimate that the human brain has more than 100 billion neurons and about one quadrillion one with 15 zeros connections between neurons constructing the world s most sophisticated machine there is perhaps no time in the human life cycle during which plasticity is more important than in the period of nervous system development a newborn baby s brain scientists have learned is not just a miniature version of an adult s instead it is a work in progress the world s most sophisticated machine in construction phase like the scaffolding that shapes the framework of a building an initial framework of interneuronal wiring is present at birth pre-set by nature via the genetic blueprints provided by the mother and father the materials are also there babies are born with virtually all of their lifetime store of nerve cells see developments in stem cell research p 23 what remains is the finish work of the brain s communications architecture the fine-tuning of a quadrillion cell-to-cell connections in humans the fine-tuning phase unfolds over several developmental years nurture largely directs the completion of the wiring process literally shaping the structure of the brain according to a child s early sensory experiences during critical periods or stages of brain development these early experiences stimulate neural activity in certain synaptic connections which in turn become stronger and thrive a pruning process ruled by a philosophy of use it or lose it ensues during which synapses that are not routinely stimulated may wither and die within that period windows of opportunity during which the brain may be specially the precise mapping of brain functions and structures and permitting scientists to search out the roots of brain disorders or injuries in addition they have helped advance a systems view of brain function according to this view no one structure or area of the brain acts alone to drive a specific behavior or mental task while certain brain areas may be specialized for certain tasks brain function relies on networks of interconnected neurons these specialized pathways enable the brain to analyze and assimilate information from external e.g sensory as well as internal e.g hormonal cues in order to respond with appropriate physical and psychological behaviors systems neuroscience helps explain how people such as victims of stroke or head trauma whose brains have been injured in a discrete site can over time redevelop the functions lost as a result of the injury nerve cells in their brains in effect forge new pathways bypassing the injured site and forming new connections as if finding a new route to get to work after discovering that a bridge is out on the usual route this ability to adapt which scientists call plasticity seems to be particularly strong in young brains but old brains routinely learn new tricks scientists have found plasticity in fact plays a critical role in the entire life cycle of the brain from its development in infancy to its continual reshaping as learning occurs to its ability to adapt to age-related 14

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revealing the workings the wonder of the human brain primed for learning certain skills such as language open according to the developmental schedule of the brain regions underlying those skills since it s well known that humans can continue to learn and modify behavior throughout life it s clear that the windows never really slam shut even though they may become a bit sticky children who fail to get the stimulation they need for proper brain development can become tragedies in the 1990s studies of romanian orphans whose cries for comfort were never oped the prefrontal cortex for example the brain s center for reason advance planning and other higher functions does not reach maturity until the early 20s since this part of the brain seems to act as a kind of cerebral brake to halt inappropriate or risky behaviors some scientists believe sluggish development may explain difficulties in resisting impulsive behavior that some adolescents exhibit at times the brain also has ultimate control over the ebb and flow of powerful hormones such as adrenaline testosterone and numerous studies have also shown that babies who are held and caressed regularly do better developmentally and may reap the benefits throughout life answered or whose smiles were never encouraged found lingering impairments in the children s basic social and thinking abilities and in their physical development numerous studies have also shown that babies who are held and caressed regularly do better developmentally and may reap the benefits throughout life the first few years of life are especially important as they are periods of rapid change in the synapses but new understandings about the developing brain indicate that the process of finetuning connections among neurons continues to varying degrees into adolescence in fact brain development probably never really ends older adults are also capable of forming new synaptic connections and do when they learn new things but the rapid-paced period during which external stimuli are critical to normal brain-building generally begins to dwindle around the mid-teen years estrogen which themselves play critical roles in the changing adolescent body the teenage brain is also struggling to adapt to a shift in the circadian rhythm the brain s internal biological clock which drives the sleepwake cycle the secretion of melatonin sets the timing for this internal clock a hormone the brain produces in response to the daily onset of darkness in one study researchers found that the further along in puberty teens were the later at night their melatonin was secreted in practice that means teens natural biological clock is telling them to go to sleep later and to stay asleep longer the aging brain attitude counts while the teenage brain faces its share of challenges as it weathers the storm of adolescence aging undoubtedly poses the greatest challenge to the normal life cycle of the brain but contrary to popular belief the slow march of mental decline many people associate with aging is not inevitable while many people do experience memory lapses as they age even as early as their 15 growing pains in the teenage brain adolescence marks a turning point of sorts for the brain as some of its structures are nearing maturity while others are not yet fully devel-

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