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This assignment will require you to type directly in this worksheet. Part I will require you to research cognitive related changes during adulthood. In each box, describe 3-4 cognitive changes that generally occur during that age-range (include things such as memory, attention, structural change, processing speed, executive functioning, and neurotransmission).

A minimum of three resources are required. Your textbook may serve as one resource. Make sure the references are current and cited both with your chart and referenced in the reference section.

I’ll be looking to see that you understand the roles that the different brain regions have. You need to include research AND your own thoughts or examples.

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Neuroscience Of 20-Somethings: ‘Emerging Adults’ Show Brain Differences

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Neuroscience Of 20-Somethings: ‘Emerging Adults’ Show Brain Differences

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In the opening scene of Lena Dunham's HBO series Girls, the Horvaths tell their 24-year-old daughter Hannah that they will no longer support her-or, as her mother puts it: "No. More. Money." A recent college graduate, Hannah has been living in Brooklyn, completing an unpaid internship and working on a series of personal essays. The Horvaths intend to give Hannah "one final push" toward, presumably, a lifestyle that more closely resembles adulthood. Hannah protests. Her voice quavers. She tells her parents that she does not want to see them the following day, even though they are leaving town soon: "I have work and then I have a dinner thing and then I am busy-trying to become who I am."

Across the United States-and in developed nations around the world-twenty-somethings like Hannah are taking longer to finish school, leave home, begin a career, get married and reach other milestones of adulthood. These trends are not just anecdotal; sociologists and psychologists have gathered supporting data. Robin Marantz Henig summarizes the patterns in her 2010 New York Times Magazine feature:

"One-third of people in their 20s move to a new residence every year. Forty percent move back home with their parents at least once. They go through an average of seven jobs in their 20s, more job changes than in any other stretch. Two-thirds spend at least some time living with a romantic partner without being married. And marriage occurs later than ever. The median age at first marriage in the early 1970s, when the baby boomers were young, was 21 for women and 23 for men; by 2009 it had climbed to 26 for women and 28 for men, five years in a little more than a generation."

These demographic shifts have transformed the late teens through mid twenties into a distinct stage of life according to Jeffrey Arnett of Clark University, who calls the new phase "emerging adulthood." Arnett acknowledges that emerging adulthood is relevant only to about 18 percent of the global population, to certain groups of twenty-somethings in developed nations such as the United States, Canada, Western Europe, Japan and Australia. To make some broad generalizations, people living in the rest of world-particularly in developing countries-are much more likely to finish formal education in their teens and marry by their early twenties.

Although Arnett primarily studies how society, culture and the economy have created emerging adulthood, some scientists and journalists have wondered whether biology is involved as well. Henig writes that some researchers think a lengthy preamble to adulthood might be "better-suited to our neurological hard-wiring" and that the general ambivalence of twenty-somethings-feeling that they are sort of adults, but not really adults- "reflects what is going on in the brain, which is also both grown-up and not-quite-grown-up." Most recently, The Wall Street Journal ran an article recommending that concerned parents of twenty-somethings should "chill out" because "recent research into how the brain develops suggests that people are better equipped to make major life decisions in their late 20s than earlier in the decade. The brain, once thought to be fully grown after puberty, is still evolving into its adult shape well into a person's third decade, pruning away unused connections and strengthening those that remain, scientists say."

After reading The Wall Street Journal article, a flock of questions began flapping in my own twenty-something mind. What does it mean to have a "fully grown" adult brain anyways and, if my peers and I do not yet have such a brain, exactly how un-grown-up are our noggins, how uncooked our noodles? Were we neurologically unfit to make the important decisions about careers and marriage that some of us have already made? If emerging adulthood is itself an emerging phenomenon, what is its precise relationship to the biology of an organ whose defining characteristics began evolving millions of years ago? And does a Peter Pan brain have any redeeming qualities?

In an ongoing study that kicked off in 1991, Jay Giedd of the National Institute of Mental Health has been tracking the brain development of nearly 4,000 people ranging in age from a few days to 96 years. Every two years, Giedd invites his volunteers to the lab to scan their brains with magnetic resonance imaging (MRI). Giedd and his colleagues have learned that, contrary to neuroscientists' earliest assumptions, the brain continues to markedly rewire itself even after puberty.

Between 12 and 25, the brain changes its structure in a few important ways. Like an overeager forest, neurons in the early adolescent brain become bushier, growing more and more overlapping branches whose twigs reach toward one another, nearly touching except for tiny gaps known as synapses. When an electrical impulse-or action potential-reaches a twig, the neuron flings spurts of chemical messages across the synapse. Over time, depending on how teens busy their minds, twigs around the least used synapses wither, while twigs flanking the most trafficked synapses grow thicker, strengthening those connections. Meanwhile, as neurons in the adolescent brain make and break connections, glia-non-firing brain cells-set to work wrapping neurons in a fatty white tissue known as myelin, considerably increasing the speed at which electrical impulses travel along neurons' branches.

Although these developmental changes continue far longer than researchers initially thought, they are not as dramatic in the twenties as they are in the teens. "In the twenties, the brain is definitely still changing, but it's not rampant biological change," explains Beatriz Luna of the University of Pittsburgh. "Most of the brain's systems are good to go in one's twenties." In an email message, B.J. Casey of Weill Cornell Medical College made a similar remark: "Most of my functional imaging work shows the greatest brain changes between 13 and 17 with relative stability across 20s."

In her own studies, Luna has found that, at least on certain cognitive tasks, people in their early twenties perform just as well as people in their late twenties. She often asks her volunteers to deliberately look away from a flashing light on a screen-a test of impulse inhibition, since flickers attract our attention. "Ten-year-olds stink at it, failing about 45 percent of the time," as David Dobbs put it in his National Geographic feature. "Teens do much better. In fact, by age 15 they can score as well as adults if they're motivated, resisting temptation about 70 to 80 percent of the time...And by age 20, their brains respond to this task much as the adults' do."

In Luna's studies, brain behavior changed in parallel with improving scores. Older volunteers showed higher activity in brain regions involved in identifying errors, such as the anterior cingulate cortex. Related research has shown that older adolescents have stronger bridges of neural tissue connecting the emotional and motor centers of their brains with the prefrontal cortex, an "executive" brain region known for, among many other things, inhibiting impulses and tempering bubbling emotions. Luna and other researchers now think that, more than the growth of any single brain region, this increasing interconnectedness characterizes brain development in the twenties. Of course, that doesn't mean that once someone leaves behind their twenties they will never again lose their cool or act thoughtlessly instead of prudently. Individual variation makes all the difference. Some teens and twenty-somethings are simply more cautious and composed than some adults.

To reflect the ongoing structural changes in the adolescent and twenty-something brain, many journalists and scientists use words and phrases like "unfinished," "work in progress," "under construction" and "half-baked." Such language implies that the brain eventually reaches a kind of ideal state when it is "done." But there is no final, optimal state. The human brain is not a soufflé that gradually expands over time and finally finishes baking at age 30. Yes, we can identify and label periods of dramatic development-or windows of heightened plasticity-but that should not eclipse the fact that brain changes throughout life.

Studies have confirmed, for example, that London taxicab drivers grow larger hippocampi as they learn to navigate London's convoluted roadways. This growth in the hippocampus, a brain region essential for forming new memories, is not explained by youth: According to the Public Carriage Office, 98 per cent of London taxi drivers are over the age of 30 [PDF]. Granted, the hippocampus is one of only two regions thought to grow new neurons in adulthood, but the brain remains remarkably plastic in other ways too. When one part of the brain shrivels-say, from stroke or traumatic injury- nearby regions often adopt their deceased neighbor's functions. When blind people learn to use echolocation, areas of their brains usually devoted to vision learn to interpret the echoes of clicks and taps instead. Neuroplasticity is an everyday phenomenon as well. The adult brain constantly strengthens and weakens connections between its cells. In fact, learning and memory are dependent on such flexibility. Learning a new language or picking up an instrument may be easier when one is young, but adaptability and creativity do not expire on one's 30th birthday.
Brains of our past and present
Mapping structural changes in the brain over time tells us how the brain matures, but not why it matures that way. To answer why we have to think about the benefits that prolonged brain development would have offered our ancestors. After all, the human brain's fundamental phases of development could not have popped into existence in the last 50 years or even thousands of years ago-more likely, they evolved at least a couple million years ago in the Paleolithic, when the human brain began to increase in size and morph into the organ we know today. Keeping the brain extra flexible for a longer period of time may have provided our ancestors with more opportunities to quickly master new skills and adapt to a changing environment. But taking too long to learn how to manage emotions, control impulses and plan ahead may also have impeded survival.

Painting an accurate tableau of the Paleolithic lifestyle is difficult because the evidence is scant, but we can say a few things with confidence. First, although the exact lifespans of early humans are not certain, evidence from the fossil record-as well as death rates among modern hunter-gatherer societies-suggests that most early humans did not live as long as people in developed nations today. Children frequently died in their first years of life. If you made it to 15, you were more likely to live at least another 15 or 20 years, but people who lived past their forties were probably in a minority. Second, early humans likely started having children far sooner than people in industrialized countries today. Paleolithic twenty-somethings, we can safely assume, did not have the luxury of spending a few years after college "finding themselves" while backpacking through India and volunteering on organic farms. Rather, people who survived to their twenties in the Paleolithic probably had to bear the responsibilities of parenthood as well as contribute substantially to their community's survival. These are not exactly circumstances that favor leisurely cognitive development late into one's twenties.

When I described this scenario to Giedd, however, he suggested that widening the window of heightened neuroplasticity to encompass one's twenties may have helped Homo sapiens adapt to rapid shifts in the climate. Unfortunately, as with many hypothesis in evolutionary psychology, scientists do not have a way to objectively test these ideas. Still, if we want to fully understand the brain, we cannot ignore the fact that it evolved in circumstances very different from our own.

For now, let's put the brains of ancient twenty-somethings out of our minds. What about the twenty-somethings of today? Even if the brain's developmental changes are more dramatic in the teens than in the twenties, the best available evidence suggests that a twenty-something's brain boasts a little more adaptability than an older brain. Our twenties might represent a final opportunity to begin mastering a particular skill with a kind of facility we cannot enjoy in later decades. Should people in their twenties buckle down and choose something, anything, to practice while their brains are still nimble? Does the neuroscience suggest that, for all their freedom and fun, gallivanting twenty-somethings neglect their last years of heightened plasticity? Should parents encourage their 20-year-olds to shirk adult responsibilities lest they hamper an advantageous period of self-discovery and wild experimentation?

Solid neuroscience that can directly answer questions like does not yet exist. "It's too soon to tell," Giedd says, "but we're wondering." He and his colleagues plan to compare the brain development of girls who become pregnant in their teens to girls who do not. "Teen pregnancy changes all your priorities and what you do with your time-how do those experiences change the brain?" Arnett agrees that such neuroimaging studies would be useful. "Even in industrialized countries, a lot of people still get married pretty early. You could do brain studies comparing people who experience their twenties differently and contrast how their brains develop."

In the meantime, twenty-somethings can expect increasingly frequent waves of sage advice from academics, bloggers and concerned parents alike. "Watching talking cats on YouTube isn't as good for cognitive development as reading or taking classes," Laurence Steinberg of Temple University told The Wall Street Journal. Truth. In the same article, Jennifer Tanner, co-chair of the Society for the Study of Emerging Adulthood, provides her own pearl: "My advice is, if your parents are currently doing things for you that you could do for yourself, take the controls. Say, 'No. Mom, Let me get my own shampoo.'" Thanks for the tip, Ms. Tanner. I mean, if I were living at home to save money, I wouldn't mind sharing the jumbo size 2-in-1 shampoo and conditioner with my siblings. But I'm pretty sure the vast majority of my peers have a handle on shampoo selection by now. Because we're worth it.

Emerging adulthood is real-it's happening, albeit to a small percentage of the world's population. Whether we can, at this moment in time, meaningfully link this life stage to neuroscience seems a tenuous proposition at best. By itself, brain biology does not dictate who we are. The members of any one age group are not reducible to a few distinguishing structural changes in the brain. Ultimately, the fact that a twenty-something has weaker bridges between various brain regions than someone in their thirties is not hugely important-it's just one aspect of a far more complex identity.

BEFORE YOU GO

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What's Different About Brains Of 20-Somethings?

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In the opening scene of Lena Dunham's HBO series Girls, the Horvaths tell their 24-year-old daughter Hannah that they will no longer support her-or, as her mother puts it: "No. More. Money." A recent college graduate, Hannah has been living in Brooklyn, completing an unpaid internship and working on a series of personal essays.

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Ask those who've entered the thick of middle age what they think about their mental capacities and you're likely to hear a slew of complaints - their brains don't work as quickly as they used to, they're distractable and unfocused, and they can never remember anyone's name.

While some of these complaints reflect real declines in brain function in our middle years, the deficiencies of a middle-aged brain have likely been overstated by anecdotal evidence and even by some scientific studies.

Contrary to its reputation as a slower, duller version of a youthful brain, it seems that the middle-aged mind not only maintains many of the abilities of youth but actually acquires some new ones. The adult brain seems to be capable of rewiring itself well into middle age, incorporating decades of experiences and behaviors. Research suggests, for example, the middle-aged mind is calmer, less neurotic and better able to sort through social situations. Some middle-agers even have improved cognitive abilities.

"There is an enduring potential for plasticity, reorganization and preservation of capacities," says cognitive neuroscientist Patricia Reuter-Lorenz, PhD, of the University of Michigan in Ann Arbor.

Researchers now have an unprecedented wealth of data on the aging brain from the Seattle Longitudinal Study, which has tracked the cognitive abilities of thousands of adults over the past 50 years. These results show that middle-aged adults perform better on four out of six cognitive tests than those same individuals did as young adults, says study leader Sherry Willis, PhD, of the University of Washington in Seattle.

While memorization skills

and perceptual speed both start to decline in young adulthood, verbal abilities, spatial reasoning, simple math abilities and abstract reasoning skills all improve in middle age.

Cognitive skills in the aging brain have also been studied extensively in pilots and air-traffic controllers. Again, older pilots show declines in processing speed and memory capacity, but their overall performance seems to remain intact. In a study published in Neurology (Vol. 68, No. 9) in 2007, researchers tested pilots age 40 to 69 as they performed on flight simulators. Older pilots took longer to learn to use the simulators but did a better job than their younger colleagues at achieving their objective: avoiding collisions.

Many middle-aged people are convinced that they're just not as mentally skilled or even as intelligent as they used to be, Willis says. But it's possible that's an illusion arising from the aspects of cognition that do suffer in middle age.

"They may get the sense they're cognitively slow just because they're perceptually slow or slow with psychomotor skills," she says, when in reality their brains are performing most tasks remarkably well.

Changing strategies

Researchers used to believe that brain activity would slow down with aging so that older brains would show less activity overall than younger ones. But functional neuroimaging studies have overturned that assumption.

For example, psychologist Cheryl Grady, PhD, of the University of Toronto, and her colleagues have found that older adults use more of their brains than young adults to accomplish certain tasks. In a study published in the Journal of Neuroscience (Vol. 3, No. 2) in 1994, Grady reported that performing a face-matching task activates mainly the occipital visual areas in younger adults, but older adults use these areas as well as the prefrontal cortex. (Both groups of adults are equally skilled at the task.)

Several groups, including Grady's, have also found that older adults tend to use both brain hemispheres for tasks that only activate one hemisphere in younger adults. Younger adults show similar bilateralization of brain activity if the task is difficult enough, Reuter-Lorenz says, but older adults use both hemispheres at lower levels of difficulty.

The strategy seems to work. According to work published in Neuroimage (Vol. 17, No. 3) in 2002, the best-performing older adults are the most likely to show this bilateralization. Older adults who continue to use only one hemisphere don't perform as well.

Reuter-Lorenz finds these changes with age encouraging, as they show that the middle-aged brain is capable of altering how it does things in order to accomplish the task at hand. "Compensation through some brain mechanisms may make up for losses in others," she says.

Grady cautions that many studies on the middle-aged brain are preliminary, as this age group "hasn't been studied very much. It certainly hasn't been studied enough." Most functional imaging studies, for example, tend to recruit college students and retirees as study subjects, Grady says. Cognitive characteristics of in-between ages are often simply extrapolated from the two ends of the spectrum.

While a linear continuum may be accurate for many traits, it may not always be a valid assumption. Grady's own work on brain activation during memory tasks, for example, suggests that the middle-aged pattern does fall between those of a young adult and an elderly person.

For example, the amount of white matter in the brain, which forms the connections among nerve cells, seems to increase until age 40 or 50 and then falls off again. "So that suggests that there are some developmental changes that really don't hit their peak until somewhere in middle age," Grady says.

At least the glasses are rose-colored

Emotions and social interactions - even personality - may systematically change as people enter middle age. Many studies have found that people become calmer and less neurotic as they age. "There's a quieting of emotional storms," Reuter-Lorenz says.

Work by cognitive psychologist Mara Mather, PhD, of the University of Southern California in Los Angeles, has found that older adults tend to focus more on positive information and less on negative information than their younger counterparts. In 2004, she and her colleagues reported in Psychological Science (Vol. 15, No. 4) that the amygdala in older adults actually responds less to negative stimuli (such as unpleasant pictures) than it does in young adults. Starting around age 40, people also show a better memory for positive images than for negative ones, and this trend continues until at least age 80.

This "positivity effect" is seen even more strongly in people who are doing exceptionally well cognitively, Mather says, "so it doesn't seem to be something that just goes along with cognitive decline; it seems to be something that's an active process."

These findings fit with many self-reports from middle-aged and older individuals, Mather says. Older adults rank emotional stability and positive affect as more important than younger adults do, and they say that they're better at regulating their own emotions than they were in their youth.

Although scientifically analyzing such qualities as judgment and wisdom is considerably more difficult than measuring psychomotor speed or memory storage capacity, some researchers are trying to do just that. Research over the past several years has reported that middle-aged people are much more expert at many social interactions - such as judging the true intentions of other human beings - than are those either younger or older.

And work by David Laibson, PhD, at Harvard University, found that adults in midlife show better economic understanding and make better financial decisions than either younger or older adults. In fact, the average person's financial judgment seems to peak at 53.

Variability and influences

One of the middle-aged mind's most striking features may not be any one feature or ability, but rather the variation in cognitive skills that's found in this age group. Although differences in cognition obviously exist among individuals at all ages, these differences seem to increase in middle age.

For example, memory and attention frequently suffer in middle age, but some individuals' abilities actually improve in midlife. In Willis's Seattle study, most participants' ability to remember lists of words declined in middle age, but about 15 percent performed better on this task than they did as young adults.

"If you study a wide range of abilities, you begin to realize how very complex cognitive decline is and how many individual differences there are," Willis says.

This variation in behavioral performance is also reflected in expression of genes related to learning and memory. In a study published in Nature in 2004 (Vol. 429, No. 6,994), the brains of adults under age 40 consistently showed little damage and high levels of expression of these genes, while brains from those over 73 showed lots of damage and low gene expression. But in the middle-aged group, results varied widely. Some middle-aged brains were already shutting down, whereas others were indistinguishable from a 30-year-old brain.

"It's a very interesting and heterogeneous group," Grady says.

With more study of middle age in general - especially of those who seem to glide through those years with cognitive abilities intact or even improving - scientists hope to enable many more people to preserve cognitive health into old age.

So far, research suggests that remaining cognitively impressive with age comes from adopting certain behaviors as well as possessing some genetic luck, Willis says. For example, researchers have identified several gene variants that are risk factors for early memory problems. But people who show cognitive improvement in midlife also tend to be more physically, cognitively and socially active than those who don't fare as well.

"Instead of a crisis, middle age should be thought of as a time for a new form of self-investment," Reuter-Lorenz says. "This time of life brings so many new opportunities to invest in your own cognitive and physical resources, so you can buffer against the effects of older age."
Melissa Lee Phillips is a writer in Seattle.

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Ask those who've entered the thick of middle age what they think about their mental capacities and you're likely to hear a slew of complaints - their brains don't work as quickly as they used to, they're distractable and unfocused, and they can never remember anyone's name.

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What's Different About Brains of 20 Somethings

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What's Different About Brains of 20 Somethings

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In the opening scene of Lena Dunham's HBO series Girls, the Horvaths tell their 24-year-old daughter Hannah that they will no longer support her-or, as her mother puts it: "No. More. Money." A recent college graduate, Hannah has been living in Brooklyn, completing an unpaid internship and working on a series of personal essays. The Horvaths intend to give Hannah "one final push" toward, presumably, a lifestyle that more closely resembles adulthood. Hannah protests. Her voice quavers. She tells her parents that she does not want to see them the following day, even though they are leaving town soon: "I have work and then I have a dinner thing and then I am busy-trying to become who I am."

Across the United States-and in developed nations around the world-twenty-somethings like Hannah are taking longer to finish school, leave home, begin a career, get married and reach other milestones of adulthood. These trends are not just anecdotal; sociologists and psychologists have gathered supporting data. Robin Marantz Henig summarizes the patterns in her 2010 New York Times Magazine feature:

"One-third of people in their 20s move to a new residence every year. Forty percent move back home with their parents at least once. They go through an average of seven jobs in their 20s, more job changes than in any other stretch. Two-thirds spend at least some time living with a romantic partner without being married. And marriage occurs later than ever. The median age at first marriage in the early 1970s, when the baby boomers were young, was 21 for women and 23 for men; by 2009 it had climbed to 26 for women and 28 for men, five years in a little more than a generation."

These demographic shifts have transformed the late teens through mid twenties into a distinct stage of life according to Jeffrey Arnett of Clark University, who calls the new phase "emerging adulthood." Arnett acknowledges that emerging adulthood is relevant only to about 18 percent of the global population, to certain groups of twenty-somethings in developed nations such as the United States, Canada, Western Europe, Japan and Australia. To make some broad generalizations, people living in the rest of world-particularly in developing countries-are much more likely to finish formal education in their teens and marry by their early twenties.

Although Arnett primarily studies how society, culture and the economy have created emerging adulthood, some scientists and journalists have wondered whether biology is involved as well. Henig writes that some researchers think a lengthy preamble to adulthood might be "better-suited to our neurological hard-wiring" and that the general ambivalence of twenty-somethings-feeling that they are sort of adults, but not really adults- "reflects what is going on in the brain, which is also both grown-up and not-quite-grown-up." Most recently, The Wall Street Journal ran an article recommending that concerned parents of twenty-somethings should "chill out" because "recent research into how the brain develops suggests that people are better equipped to make major life decisions in their late 20s than earlier in the decade. The brain, once thought to be fully grown after puberty, is still evolving into its adult shape well into a person's third decade, pruning away unused connections and strengthening those that remain, scientists say."

After reading The Wall Street Journal article, a flock of questions began flapping in my own twenty-something mind. What does it mean to have a "fully grown" adult brain anyways and, if my peers and I do not yet have such a brain, exactly how un-grown-up are our noggins, how uncooked our noodles? Were we neurologically unfit to make the important decisions about careers and marriage that some of us have already made? If emerging adulthood is itself an emerging phenomenon, what is its precise relationship to the biology of an organ whose defining characteristics began evolving millions of years ago? And does a Peter Pan brain have any redeeming qualities?

In an ongoing study that kicked off in 1991, Jay Giedd of the National Institute of Mental Health has been tracking the brain development of nearly 4,000 people ranging in age from a few days to 96 years. Every two years, Giedd invites his volunteers to the lab to scan their brains with magnetic resonance imaging (MRI). Giedd and his colleagues have learned that, contrary to neuroscientists' earliest assumptions, the brain continues to markedly rewire itself even after puberty.

Between 12 and 25, the brain changes its structure in a few important ways. Like an overeager forest, neurons in the early adolescent brain become bushier, growing more and more overlapping branches whose twigs reach toward one another, nearly touching except for tiny gaps known as synapses. When an electrical impulse-or action potential-reaches a twig, the neuron flings spurts of chemical messages across the synapse. Over time, depending on how teens busy their minds, twigs around the least used synapses wither, while twigs flanking the most trafficked synapses grow thicker, strengthening those connections. Meanwhile, as neurons in the adolescent brain make and break connections, glia-non-firing brain cells-set to work wrapping neurons in a fatty white tissue known as myelin, considerably increasing the speed at which electrical impulses travel along neurons' branches.

Although these developmental changes continue far longer than researchers initially thought, they are not as dramatic in the twenties as they are in the teens. "In the twenties, the brain is definitely still changing, but it's not rampant biological change," explains Beatriz Luna of the University of Pittsburgh. "Most of the brain's systems are good to go in one's twenties." In an email message, B.J. Casey of Weill Cornell Medical College made a similar remark: "Most of my functional imaging work shows the greatest brain changes between 13 and 17 with relative stability across 20s."

In her own studies, Luna has found that, at least on certain cognitive tasks, people in their early twenties perform just as well as people in their late twenties. She often asks her volunteers to deliberately look away from a flashing light on a screen-a test of impulse inhibition, since flickers attract our attention. "Ten-year-olds stink at it, failing about 45 percent of the time," as David Dobbs put it in his National Geographic feature. "Teens do much better. In fact, by age 15 they can score as well as adults if they're motivated, resisting temptation about 70 to 80 percent of the time...And by age 20, their brains respond to this task much as the adults' do."

In Luna's studies, brain behavior changed in parallel with improving scores. Older volunteers showed higher activity in brain regions involved in identifying errors, such as the anterior cingulate cortex. Related research has shown that older adolescents have stronger bridges of neural tissue connecting the emotional and motor centers of their brains with the prefrontal cortex, an "executive" brain region known for, among many other things, inhibiting impulses and tempering bubbling emotions. Luna and other researchers now think that, more than the growth of any single brain region, this increasing interconnectedness characterizes brain development in the twenties. Of course, that doesn't mean that once someone leaves behind their twenties they will never again lose their cool or act thoughtlessly instead of prudently. Individual variation makes all the difference. Some teens and twenty-somethings are simply more cautious and composed than some adults.

To reflect the ongoing structural changes in the adolescent and twenty-something brain, many journalists and scientists use words and phrases like "unfinished," "work in progress," "under construction" and "half-baked." Such language implies that the brain eventually reaches a kind of ideal state when it is "done." But there is no final, optimal state. The human brain is not a soufflé that gradually expands over time and finally finishes baking at age 30. Yes, we can identify and label periods of dramatic development-or windows of heightened plasticity-but that should not eclipse the fact that brain changes throughout life.

Studies have confirmed, for example, that London taxicab drivers grow larger hippocampi as they learn to navigate London's convoluted roadways. This growth in the hippocampus, a brain region essential for forming new memories, is not explained by youth: According to the Public Carriage Office, 98 per cent of London taxi drivers are over the age of 30 [PDF]. Granted, the hippocampus is one of only two regions thought to grow new neurons in adulthood, but the brain remains remarkably plastic in other ways too. When one part of the brain shrivels-say, from stroke or traumatic injury- nearby regions often adopt their deceased neighbor's functions. When blind people learn to use echolocation, areas of their brains usually devoted to vision learn to interpret the echoes of clicks and taps instead. Neuroplasticity is an everyday phenomenon as well. The adult brain constantly strengthens and weakens connections between its cells. In fact, learning and memory are dependent on such flexibility. Learning a new language or picking up an instrument may be easier when one is young, but adaptability and creativity do not expire on one's 30th birthday.
Brains of our past and present
Mapping structural changes in the brain over time tells us how the brain matures, but not why it matures that way. To answer why we have to think about the benefits that prolonged brain development would have offered our ancestors. After all, the human brain's fundamental phases of development could not have popped into existence in the last 50 years or even thousands of years ago-more likely, they evolved at least a couple million years ago in the Paleolithic, when the human brain began to increase in size and morph into the organ we know today. Keeping the brain extra flexible for a longer period of time may have provided our ancestors with more opportunities to quickly master new skills and adapt to a changing environment. But taking too long to learn how to manage emotions, control impulses and plan ahead may also have impeded survival.

Painting an accurate tableau of the Paleolithic lifestyle is difficult because the evidence is scant, but we can say a few things with confidence. First, although the exact lifespans of early humans are not certain, evidence from the fossil record-as well as death rates among modern hunter-gatherer societies-suggests that most early humans did not live as long as people in developed nations today. Children frequently died in their first years of life. If you made it to 15, you were more likely to live at least another 15 or 20 years, but people who lived past their forties were probably in a minority. Second, early humans likely started having children far sooner than people in industrialized countries today. Paleolithic twenty-somethings, we can safely assume, did not have the luxury of spending a few years after college "finding themselves" while backpacking through India and volunteering on organic farms. Rather, people who survived to their twenties in the Paleolithic probably had to bear the responsibilities of parenthood as well as contribute substantially to their community's survival. These are not exactly circumstances that favor leisurely cognitive development late into one's twenties.

When I described this scenario to Giedd, however, he suggested that widening the window of heightened neuroplasticity to encompass one's twenties may have helped Homo sapiens adapt to rapid shifts in the climate. Unfortunately, as with many hypothesis in evolutionary psychology, scientists do not have a way to objectively test these ideas. Still, if we want to fully understand the brain, we cannot ignore the fact that it evolved in circumstances very different from our own.

For now, let's put the brains of ancient twenty-somethings out of our minds. What about the twenty-somethings of today? Even if the brain's developmental changes are more dramatic in the teens than in the twenties, the best available evidence suggests that a twenty-something's brain boasts a little more adaptability than an older brain. Our twenties might represent a final opportunity to begin mastering a particular skill with a kind of facility we cannot enjoy in later decades. Should people in their twenties buckle down and choose something, anything, to practice while their brains are still nimble? Does the neuroscience suggest that, for all their freedom and fun, gallivanting twenty-somethings neglect their last years of heightened plasticity? Should parents encourage their 20-year-olds to shirk adult responsibilities lest they hamper an advantageous period of self-discovery and wild experimentation?

Solid neuroscience that can directly answer questions like does not yet exist. "It's too soon to tell," Giedd says, "but we're wondering." He and his colleagues plan to compare the brain development of girls who become pregnant in their teens to girls who do not. "Teen pregnancy changes all your priorities and what you do with your time-how do those experiences change the brain?" Arnett agrees that such neuroimaging studies would be useful. "Even in industrialized countries, a lot of people still get married pretty early. You could do brain studies comparing people who experience their twenties differently and contrast how their brains develop."

In the meantime, twenty-somethings can expect increasingly frequent waves of sage advice from academics, bloggers and concerned parents alike. "Watching talking cats on YouTube isn't as good for cognitive development as reading or taking classes," Laurence Steinberg of Temple University told The Wall Street Journal. Truth. In the same article, Jennifer Tanner, co-chair of the Society for the Study of Emerging Adulthood, provides her own pearl: "My advice is, if your parents are currently doing things for you that you could do for yourself, take the controls. Say, 'No. Mom, Let me get my own shampoo.'" Thanks for the tip, Ms. Tanner. I mean, if I were living at home to save money, I wouldn't mind sharing the jumbo size 2-in-1 shampoo and conditioner with my siblings. But I'm pretty sure the vast majority of my peers have a handle on shampoo selection by now. Because we're worth it.

Emerging adulthood is real-it's happening, albeit to a small percentage of the world's population. Whether we can, at this moment in time, meaningfully link this life stage to neuroscience seems a tenuous proposition at best. By itself, brain biology does not dictate who we are. The members of any one age group are not reducible to a few distinguishing structural changes in the brain. Ultimately, the fact that a twenty-something has weaker bridges between various brain regions than someone in their thirties is not hugely important-it's just one aspect of a far more complex identity.

BEFORE YOU GO

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What's Different About Brains Of 20-Somethings?

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In the opening scene of Lena Dunham's HBO series Girls, the Horvaths tell their 24-year-old daughter Hannah that they will no longer support her-or, as her mother puts it: "No. More. Money." A recent college graduate, Hannah has been living in Brooklyn, completing an unpaid internship and working on a series of personal essays.

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Cite our Text

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The Teen Brain: Still Under Construction

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Publications about Brain Anatomy and Physiology

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Lists NIMH Publications about Brain Anatomy and Physiology.

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Abstract

Ageing causes changes to the brain size, vasculature, and cognition. The brain shrinks with increasing age and there are changes at all levels from molecules to morphology. Incidence of stroke, white matter lesions, and dementia also rise with age, as does level of memory impairment and there are changes in levels of neurotransmitters and hormones. Protective factors that reduce cardiovascular risk, namely regular exercise, a healthy diet, and low to moderate alcohol intake, seem to aid the ageing brain as does increased cognitive effort in the form of education or occupational attainment. A healthy life both physically and mentally may be the best defence against the changes of an ageing brain. Additional measures to prevent cardiovascular disease may also be important.

Keywords: ageing, brain, cognition

The effects of ageing on the brain and cognition are widespread and have multiple aetiologies. Ageing has its effects on the molecules, cells, vasculature, gross morphology, and cognition. As we age our brains shrink in volume, particularly in the frontal cortex. As our vasculature ages and our blood pressure rises the possibility of stroke and ischaemia increases and our white matter develops lesions. Memory decline also occurs with ageing and brain activation becomes more bilateral for memory tasks. This may be an attempt to compensate and recruit additional networks or because specific areas are no longer easily accessed. Genetics, neurotransmitters, hormones, and experience all have a part to play in brain ageing. But, it is not all negative, higher levels of education or occupational attainment may act as a protective factor. Also protective are a healthy diet, low to moderate alcohol intake, and regular exercise. Biological ageing is not tied absolutely to chronological ageing and it may be possible to slow biological ageing and even reduce the possibility of suffering from age related diseases such as dementia.

Physical changes

Cognitive change

The most widely seen cognitive change associated with ageing is that of memory. Memory function can be broadly divided into four sections, episodic memory, semantic memory, procedural memory, and working memory.18 The first two of these are most important with regard to ageing. Episodic memory is defined as "a form of memory in which information is stored with 'mental tags', about where, when and how the information was picked up".19 An example of an episodic memory would be a memory of your first day at school, the important meeting you attended last week, or the lesson where you learnt that Paris is the capital of France. Episodic memory performance is thought to decline from middle age onwards. This is particularly true for recall in normal ageing and less so for recognition.20 It is also a characteristic of the memory loss seen in Alzheimer's disease (AD).18

Semantic memory is defined as "memory for meanings", for example, knowing that Paris is the capital of France, that 10 millimetres make up a centimetre, or that Mozart composed the Magic Flute.19 Semantic memory increases gradually from middle age to the young elderly but then declines in the very elderly.20 It is not yet clear why these changes occur and it has been hypothesised that the very elderly have less resources to draw on and that their performance may be affected in some tasks by slower reaction times, lower attentional levels, slower processing speeds, detriments in sensory and or perceptual functions, or potentially a lesser ability to use strategies.20,21,22,23

There have been studies investigating different types of memory in ageing using neuropsychological testing and neuroimaging. However, it must be pointed out that it is sometimes methodologically difficult to separate some of these functions, for example episodic memory encoding and semantic memory retrieval.24 Despite this studies are beginning to examine performance on memory tasks with ageing and by neuroimaging. A review article focusing in this area highlighted the changes in regional brain activation.24 Older brains tend to show more symmetrical activation, either because they have increased activation in a hemisphere that is less activated than in younger adults or because they show reduced activation in the areas most activated in younger adults. This has been shown for visual perception and in memory tasks.24 The observed changes in activation in the left and right prefrontal cortex are in keeping with changes in memory performance, particularly episodic memory, as this is thought to be based in this area.24 It has also been suggested that the actual level of brain activation, as shown in neuroimaging, may be related more directly to the levels of memory performance.25 A review of studies using electroencephalograms to examine event related potentials in response to stimuli also contribute some support for increased symmetry in brain activation with age.26

The increased symmetrical hemispheric activation is a robust finding and has been referred to as HAROLD or hemispheric asymmetry reduction in older adults. It is not clear whether this change is an attenuation of the response seen in younger subjects, an inability to recruit specific areas, or an attempt to compensate for the ageing process.21,23,25 This change in activation occurring in the frontal lobes fits with changes in memory performance and with the possible white matter changes referred to above, however, other factors such as changes in neurotransmitter or hormone levels also require consideration.

Mechanisms of change

Another factor to consider with regard to the ageing brain and its cognitive performance is hormonal influence. It is known that sex hormones can affect cognitive processes in adulthood and that changes in sex hormones occur in ageing particularly in women at menopause. Women also have a higher incidence of AD even when longer life expectancy is taken into account.14 AD is characterised by failing memory and there has been a suggestion that oestrogen therapy may increase dopaminergic responsivity32 and play a protective part in AD.33,34 It must be remembered though that the use of HRT has recently been shown to have cancer risks.35 Growth hormone levels also decline with age and may be associated with cognitive performance although the evidence is far from clear.36

The ageing brain may also suffer from impaired glucose metabolism20 or a reduced input of glucose or oxygen as cerebrovascular efficiency falls, although reduction in glucose may partly be attributable to atrophy rather than any change in glucose metabolism.37 Change in vasculature is important and another common finding in elderly brains related to ischaemia are white matter lesions and stroke.

Vascular factors and dementia

Increasing evidence points to vascular factors not only contributing to cognitive problems in ageing but also to the two most common dementias seen in this population. The prevalence of dementia increases almost exponentially with increasing age with around 20% of those aged 80 affected rising to 40% of those aged 90.39

Protective factors

Conclusion

That the brain changes with increasing chronological age is clear, however, less clear is the rate of change, the biological age of the brain, and the processes involved. The brain changes that may affect cognition and behaviour occur at the levels of molecular ageing, intercellular and intracellular ageing, tissue ageing, and organ change. There are many areas of research under investigation to elucidate the mechanisms of ageing and to try to alleviate age associated disorders, particularly dementias that have the biggest impact on the population. In terms of personal brain ageing the studies suggest that a healthy lifestyle that reduces cardiovascular risk will also benefit the brain. Medical care in this area may even offer limited protection in terms of cognitive decline but this needs to be shown for antihypertensives, antiplatelet, and anticholesterol agents. It is also important to take note of the limitations in studies on the ageing brain. Many studies are cross sectional in nature, have small numbers of participants with wide ranges in chronological age, lack control for risk factors or protective factors, take no account of education that may improve performance on cognitive tests, and finally lack assessment with regard to depression that may also affect performance. It must be remembered that the brains of an elderly group may show cohort effects related to wider environmental influences, for example, lack of high energy foods while growing up.2 It is also extremely difficult to separate out and measure single cognitive processes to fully understand any changes.106

Future studies need to take full account of these factors and "cross sequential", a combination of cross sectional and longitudinal studies, have been proposed.3 It is clear that our understanding of the ageing brain continues to grow but still requires much research that is especially important given the numbers of elderly people in society and their potential levels of cognitive impairment. Where appropriate, randomised controlled trials of therapeutic measures may, in future, lead the way to greater understanding.

Abbreviations

AD - Alzheimer's disease

WML - white matter lesion

VaD - vascular dementia

Footnotes

Funding: none.

Conflicts of interest: none.

References

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21. Cabeza R. Commentary: neuroscience frontiers of cognitive ageing: approaches to cognitive neuroscience of ageing. In: Dixon R, Bäckman L, Nilsson L, eds. New frontiers in cognitive ageing. Oxford: Oxford University Press, 2004179-198.

27. Mukherjee J, Christian B, Dunigan K.[ et al Brain imageing of ¹⁸F‐Fallypride in normal volunteers: blood analysis, distribution, test‐retest studies, and preliminary assessment of sensitivity to ageing effects on dopamine D‐2/D‐3 receptors. Synapse 200246170-188. [ PubMed] Google Scholar]

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Articles from Postgraduate Medical Journal are provided here courtesy of BMJ Publishing Group

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Ageing causes changes to the brain size, vasculature, and cognition. The brain shrinks with increasing age and there are changes at all levels from molecules to morphology. Incidence of stroke, white matter lesions, and dementia also rise with age, as ...

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Chapter 1 Changes in Cognitive Function in Human Aging

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Chapter 1 Changes in Cognitive Function in Human Aging

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A. Attention

Attention is a basic but complex cognitive process that has multiple sub-processes specialized for different aspects of attentional processing. Some form of attention is involved in virtually all other cognitive domains, except when task performance has become habitual or automatic. Declines in attention can therefore have broad-reaching effects on one's ability to function adequately and efficiently in everyday life. The construct of attention defies simple definition, however, and it has been partitioned in a variety of ways by different researchers and theorists. The divisions used here are those that have been investigated most extensively in normal aging (for a comprehensive review of attention and aging, see [ 3]).

1. Selective Attention

Selective attention refers to the ability to attend to some stimuli while disregarding others that are irrelevant to the task at hand. For example, in visual search tasks, people are asked to search a visual display for a target letter that is surrounded by other nontarget letters. The task can be made more difficult by increasing the similarity of targets and distractors (e.g., search for an F in a background of Es), or by increasing the number of relevant or irrelevant features that are part of the search criteria. In another task - the Stroop task - people are asked to name the color of ink in which an incongruent color word is printed, (e.g., the word "red" printed in green). Here, the word information tends to interfere with color naming, causing errors and an increase in response times. To perform well in these kinds of tasks, people have to select the relevant stimulus or dimensions for processing and ignore the irrelevant ones. Although findings are not entirely consistent across studies and may differ across tasks, in general older adults appear to be slower than younger adults in responding to the targets, but are not differentially affected by distraction [ 3, 4]. Thus, deficits found in many of these tasks can be largely attributed to a general slowing of information processing in older adults rather than to selective attention deficits per se.

2. Divided Attention and Attention Switching

Divided attention has usually been associated with significant age-related declines in performance, particularly when tasks are complex. Divided attention tasks require the processing of two or more sources of information or the performance of two or more tasks at the same time. For example, people may have to monitor stimuli at two different spatial locations, or they may be asked to make semantic judgments about visually presented words while simultaneously monitoring for the occurrence of an auditorily presented digit [ 5]. The cost of dividing attention is assessed by comparing performance under dual task conditions to performance when the tasks are performed separately. Results suggest that older adults are more affected by the division of attention than young adults, particularly when the attentional demands of the two tasks are high. In addition, older adults seem less able to allocate resources appropriately when instructions are given to vary task priority [ 6]. These findings cannot be completely accounted for by a general slowing of information processing, but instead are usually explained in terms of declining processing resources associated with normal aging. Such limited resources are over-extended in older adults when attention must be divided between two or more sources. Similarly, the performance of older adults is slowed to a greater degree than that of young adults when attention must be switched from one task to another, requiring a change of mental set [ 4].

There is evidence that age deficits in divided attention and attention switching can be reduced by practice or extended training [ 7] and by aerobic exercise [ 8]. The exact mechanism of such improvements, however, is unclear. In the case of task-specific training, it is possible that some aspects of the tasks become automatic with practice, thus requiring fewer attentional resources. Alternatively, participants may develop strategies with extensive training that reduce the attentional demands of the tasks. It has been hypothesized that cardiovascular fitness may improve the efficiency of neural processes or may provide increased metabolic resources for task performance. Interestingly, the enhancement effects of aerobic exercise appear to be greatest on tasks involving executive control of attention [ 9], which depend largely on prefrontal cortex.

3. Sustained Attention

Sustained attention refers to the ability to maintain concentration on a task over an extended period of time. Typically, vigilance tasks are used to measure sustained attention, in which people must monitor the environment for a relatively infrequent signal, such as a blip on a radar screen. In general, older adults are not impaired on vigilance tasks.

4. Attention: Summary and Implications

Older adults show significant impairments on attentional tasks that require dividing or switching of attention among multiple inputs or tasks. They show relative preservation of performance on tasks that require selection of relevant stimuli; and although they are slower than young adults, they are not differentially impaired by distraction. They also are able to maintain concentration for an extended period of time. The tasks on which older adults show impairments tend to be those that require flexible control of attention, a cognitive function associated with the frontal lobes. Importantly, these types of tasks appear to be amenable to training and show benefits of cardiovascular fitness.

Attentional deficits can have a significant impact on an older person's ability to function adequately and independently in everyday life. One important aspect of daily functioning affected by attentional problems is driving, an activity that, for many older people, is essential to independence. Driving requires a constant switching of attention in response to environmental contingencies. Attention must be divided between driving, monitoring the environment, and sorting out relevant from irrelevant stimuli in a cluttered visual array. Research has shown that divided attention impairments are significantly associated with increased automobile accidents in older adults [ 3, 10]. Given the previously noted findings of the effects of practice, extended training on driving simulators under divided attention conditions may be an important remedial activity for older people.

B. Working Memory

Working memory is a multidimensional cognitive construct that has been hypothesized as the fundamental source of age-related deficits in a variety of cognitive tasks, including long-term memory, language, problem solving, and decision making. In fact, the majority of theories of cognitive aging seem to implicate working memory. Although there are several models of working memory, all agree that it is a limited capacity system that involves the active manipulation of information that is currently being maintained in focal attention (for reviews, see [ 11-13]). Short-term or primary memory, on the other hand, involves the simple maintenance of information over a short period of time. For example, one might maintain a phone number in short-term memory by simple rehearsal of the number. Older adults show minimal or no deficits in short-term memory and can typically hold about 7 ± 2 digits in mind as long as the digits are being rehearsed. Repeating the numbers backwards, however, requires an active reorganization or manipulation of the information held in short-term memory. This task thus requires working memory and shows impairments with age. In some sense, working memory is really a divided attention task - the contents of short-term memory must be maintained while simultaneously being manipulated or processed for some other purpose. Given the previously discussed findings of divided attention deficits with increased age, it is not surprising that older adults are impaired in working memory.

In the original working memory model of Baddeley and Hitch [ 14], the manipulation of information in short-term memory was handled by a central executive, and deficits in working memory were viewed as deficits in executive control, a function attributed primarily to prefrontal cortex. Recent neuroimaging research [ 15] has confirmed a role for dorsolateral prefrontal cortex (PFC) in the manipulation and updating of information in working memory, with left PFC involved more in verbal tasks and right PFC in visuospatial tasks. In recent years, however, the role of the central executive has been expanded to cover a range of executive control functions other than those associated strictly with working memory. These are elaborated in a later chapter section.

Although there is a general consensus that working memory is impaired in older adults, there is disagreement concerning the mechanisms involved, and much of the research has focused on testing a variety of theories. The next subsection outlines the main theories of working memory.

1. Theories of Working Memory

Three theories of cognitive aging have been articulated within the context of working memory deficits, although they may apply more broadly across other cognitive domains: (1) one theory proposes a reduction of attentional resources, (2) one focuses on reduced speed of information processing, and (3) one ascribes problems to a failure of inhibitory control (for review, see [ 16]).

a. Attentional Resources

Theories of age-related decline in working memory generally assume some reduction in processing resources. Craik and colleagues [ 17, 18] have suggested that the resource limitation is attentional and reflects a reduction in mental energy. Tasks with high attentional demands show impairments, whereas tasks requiring little or no attention (i.e., that are relatively automatic) are largely intact. Working memory tasks by their very nature involve divided attention and are therefore more likely to strain the limited resources of older adults. This theory is intuitively appealing, but it seems more descriptive than explanatory. The construct of attentional resources is poorly defined; and although neurophysiological correlates such as arousal or neural efficiency have been suggested [ 3], they have not been demonstrated empirically.

b. Speed of Information Processing

Salthouse [ 19] has suggested that speed of processing might be considered a resource, and that age-related deficits in working memory and other cognitive tasks can be explained in terms of a general slowing of information processing. There is little disagreement that older adults are slower than younger adults and that slowing of fundamental cognitive processes may have detrimental effects on more complex tasks. Debate has focused, instead, on whether a generalized slowing can account for the bulk of the empirical findings or whether more process-specific components are also needed. Salthouse [ 20, 21] has demonstrated in numerous studies that slowing of information processing can account for a large proportion of the age-related variance in a variety of cognitive tasks, including working and long-term memory, and has argued that speed of processing is a cognitive primitive. Other investigators [ 22], however, have suggested that speed of processing and working memory provide independent contributions to higher-level cognition, and that working memory deficits must therefore be accounted for in terms of something other than speed. Finally, at some level, slowed processing, like attentional resources, is more a descriptor of aging cognition than an explanation for cognitive deficits and says nothing about what causes slowing with age. Here too, therefore, discovery of neurophysiological correlates may help to clarify mechanisms.

c. Inhibitory Control

Hasher, Zacks, and May [ 23, 24] proposed that a lack of inhibitory control might account for cognitive deficits associated with aging. Specifically, failure to suppress irrelevant information in working memory may effectively reduce its capacity, denying access to relevant information. For example, working memory span tasks involve the successive presentation across trials of increasingly long strings of digits or words. Age deficits could be attributable to the failure to delete from working memory digits or words from prior trials, thus reducing the "working space" for new stimuli [ 25]. Although considerable data suggest that older adults experience more interference from irrelevant information under some conditions [ 26], findings are mixed and other data fail to support an inhibitory deficit account [ 3]. It may be that there are different kinds of inhibition or that age-related effects are task- or paradigm-specific.

2. Working Memory: Summary and Implications

Older adults exhibit significant deficits in tasks that involve active manipulation, reorganization, or integration of the contents of working memory. Although the mechanisms underlying these age-related deficits are as yet poorly understood, the effects of such deficits are very likely far-reaching. Many complex everyday tasks such as decision-making, problem-solving, and the planning of goal-directed behaviors require the integration and reorganization of information from a variety of sources. It seems likely that attention, speed of information processing, and the ability to inhibit irrelevant information are all important functions for effective performance of these higher-level cognitive tasks. Whether these functions might be subsumed under a domain-general executive controller that is impaired by normal aging -something akin to the central executive in Baddeley's model of working memory - or whether there may be multiple control processes that are independently affected by aging, is currently an issue under investigation. The brain regions that are active during working memory tasks are also beginning to be identified in a variety of functional neuroimaging studies. Results suggest that different areas are activated in young and old adults, particularly within the prefrontal cortex, indicating that younger and older adults are performing these tasks differently [ 12]. An understanding of age-related neurophysiological changes may help to account for these differences.

C. Long-Term Memory

The cognitive domain that has probably received the most attention in normal aging is memory (for reviews, see [ 13, 27]). Many older adults complain of increased memory lapses as they age, and a major focus of research has been to try to distinguish memory declines attributable to normal aging from those that are indicative of pathological aging, particularly Alzheimer's disease. Like attention, memory is not a unitary construct; some kinds of memory remain relatively intact with age while others show significant declines. Long-term memory, unlike short-term and working memory, requires retrieval of information that is no longer present or being maintained in an active state. This information could have occurred a few minutes ago or been acquired many years ago. The next subsections review age-related changes in various kinds of long-term memory.

1. Episodic Memory

Episodic memory refers to memory for personally experienced events that occurred in a particular place and at a particular time. This kind of memory allows one to think back through subjective time - what Tulving calls mental time travel [ 28] -and it usually evokes an "I remember" response. Episodic memory may be distinctly human; it is the most advanced form of memory and is ontogenetically the latest to develop. It also seems the most susceptible to brain damage and the most affected by normal aging.

The episodic memory problems experienced by older adults may involve deficient encoding, storage, or retrieval processes. At the input stage, older adults may encode new information less meaningfully or with less elaboration, so that memory traces are less distinctive, more similar to others in the memory system, and thereby more difficult to retrieve [ 29]. Alternatively, older people may attend to focal or salient information but fail to take account of peripheral detail, or they may fail to integrate contextual aspects of an experience with central content - what is sometimes referred to as a source memory problem [ 30]. Many of the common everyday memory lapses reported by normal older adults, such as forgetting where they parked their cars, likely involve poor encoding. These kinds of memory failures have generally been attributed to reduced use of effortful encoding strategies, which depend particularly on prefrontal brain regions. Another possibility is that noticing and integrating the various aspects of an experience involve divided attention and require working memory.

Older adults may also experience problems at the level of storage or consolidation. This aspect of episodic memory critically depends on medial temporal lobe structures, particularly the hippocampus. Consolidation is thought to involve the binding of various aspects of experience into a composite memory trace. What may be particularly critical for episodic memory and impaired in older adults is the extent to which an event is bound to its spatial and temporal context.

Finally, considerable evidence points to retrieval as a source of episodic memory problems in aging. Although it is clear that retrieval is at least partly dependent on encoding (i.e., well-encoded information is easier to retrieve), there are also effortful retrieval processes that appear to be impaired by aging. Older adults tend to show deficits on tests of free recall, to a somewhat lesser degree in cued recall, but minimally in recognition memory. Craik [ 18] has argued that the requirement to self-initiate strategic search processes in recall taxes the limited resources of older people. To the extent that environmental support can be provided at retrieval as well as at encoding (by providing good cues or using recognition tests, for example), the resource demands of encoding and retrieval are reduced and age differences are minimal. Similarly, Jennings and Jacoby [ 31] have demonstrated that recollection, which requires effortful retrieval of episodic detail, is impaired with age, whereas the more automatic judgments of familiarity are intact. Evidence from functional neuroimaging and neuropsychological studies suggests that these more strategic retrieval processes depend on the prefrontal cortex, as well as the hippocampus [ 32, 33].

2. Semantic Memory

Semantic memory refers to one's store of general knowledge about the world, including factual information such as "George Washington was the first president of the United States" and knowledge of words and concepts. Such information is not tied to the space or time of learning, and its retrieval is generally prefaced with "I know." Normally aging older adults do not have significant impairments in semantic memory. In fact, their knowledge of the world often exceeds that of young people. In addition, although access to information may be somewhat slower (particularly for words and names), the organization of the knowledge system seems unchanged with age (for review, see [ 34]). Semantic memories are believed to be stored in a variety of regions in posterior neocortex.

3. Autobiographical Memory

Autobiographical memory involves memory for one's personal past and includes memories that are both episodic and semantic in nature. The bulk of the evidence suggests that recent memories are easiest to retrieve, those from early childhood are most difficult to retrieve, and there is a monotonic decrease in retention from the present to the most remote past, with one exception. Events that occurred between the ages of 15 and 25 are recalled at a higher rate - what is referred to as the reminiscence bump - a finding that has usually been attributed to the greater salience or emotionality of the memories during this time period. This general pattern holds across all ages, suggesting that autobiographical memory is largely preserved with age (for review, see [ 35]). More detailed analyses of the nature of the autobiographical information retrieved, however, has suggested that although memory for personal semantics is intact in old age, memory for specific episodic or contextual details about one's personal past may be impaired. In a recent study, Levine et al. [ 36] observed that although older adults reported the gist of autobiographical event memories as well as young people, they reported fewer details. There may be exceptions to this finding, however. Recent studies of flashbulb memory have demonstrated that older adults remember as much as young adults about the details and circumstances surrounding highly emotional public events such as the death of Princess Diana or the 9/11 attack on the World Trade Center in New York City [ 37, 38].

4. Procedural Memory

Procedural memory refers to knowledge of skills and procedures such as riding a bicycle, playing the piano, or reading a book. These highly skilled activities are acquired more slowly than episodic memories through extensive practice. Once acquired, procedural memories are expressed rather automatically in performance and are not amenable to description (i.e., it is not easy to say "how" one reads). When talking about procedural memory or knowledge, one is likely to say, "I know how to." In general, older adults show normal acquisition of procedural skills in both motor and cognitive domains and retain them across the lifespan. With high levels of expertise, there is often little slowing of skilled performance with age (at least until the very oldest ages), although some individual components of the skill may decline. So, for example, although the finger movements of a skilled typist slow down with age, overall typing speed is maintained because other aspects of the skill adjust (e.g., scanning further ahead in the text to be typed) [ 39]. Procedural memory depends on several brain regions, including the basal ganglia and the cerebellum.

5. Implicit Memory

Implicit memory refers to a change in behavior that occurs as a result of prior experience, although one has no conscious or explicit recollection of that prior experience. For example, laboratory experiments have shown that it is easier to identify a degraded stimulus (e.g., from a brief exposure or partial information) if the stimulus was seen previously, even if one does not remember the prior occurrence. This "priming" probably occurs ubiquitously in everyday life and appears relatively intact in normal aging, although there are some inconsistencies in the literature (for review, see [ 40]). The most extensively studied form of implicit memory is perceptual priming, which occurs in response to a perceptual cue. Perceptual priming is modality specific and depends on sensory processing areas of the brain (e.g., in the visual domain, priming involves extra-striate regions of the visual cortex). Conceptual priming, which requires semantic processing and is observed in response to a conceptual cue, is also preserved in many older adults, and has been associated with left frontal and left temporal cortical regions.

6. Prospective Memory

Much of what we have to remember in everyday life involves prospective memory - remembering to do things in the future, such as keep appointments, return a book to the library, or pay bills on time (for review, see [ 41]). Older adults do quite well on these daily tasks, using a variety of external aids such as calendars and appointment books to remind themselves of these activities. Certain habitual tasks such as taking medications at the appropriate times each day, however, may create difficulties for older people. For these tasks, there often are no salient reminders or cues in the environment, and so the tasks require the kinds of self-initiated activities that seem to be particularly problematic for older adults. Prospective memory may also rely on some aspect of working memory to maintain future intentions over time and likely also involves divided attention, both functions that show age-related deficits. Prospective memory and episodic memory tend not to be correlated and probably depend on different regions of the prefrontal cortex.

7. Long-Term Memory: Summary and Implications

Aging principally affects episodic memory, namely memory for specific events or experiences that occurred in the past. Although many older adults believe that their memories for remote events are better than their memories for recent events, it is likely that older memories have become more semantic or gistlike, retaining the general core information but lacking details, particularly spatial and temporal context. These older memories have often joined the realm of things that we now "know." More problematic for older adults is remembering context or source information: where or when something was heard or read, or even whether something actually happened or was just thought about, what has been called "reality monitoring" [ 42]. Encoding and retrieval of these kinds of specific or peripheral details about a prior event may be particularly demanding of attentional resources, and good cues for the retrieval of such information may often be lacking. Although semantic memory is largely preserved in old age, the fact that what is retrieved from semantic memory is general knowledge, not specific detail, may contribute to the absence of age differences. The exception to this pattern might be the retrieval of a person's name or a specific word for a specific context, both of which show deficits in normal aging. The specificity of the information to be retrieved may therefore be a critical determinant of age differences [ 43]. There is some suggestion that age-related deficits in memory may be reduced for emotionally arousing events or materials [ 38], and so emotional or personal investment in an experience may be an important variable in episodic memory in older adults. High levels of emotion or stress, however, generally have negative effects on memory.

D. Perception

Most people view perception as a set of processes that occurs prior to cognition. However, the boundaries between perception and cognition are unclear, and much evidence suggests that these domains are interactive with top-down cognitive processes affecting perception and perceptual processing having a clear impact on cognition. Evidence indicates that perceptual function is reduced in most older adults and is not always correctable by external aids (for review, see [ 44]). This suggests, at the very least, that researchers should pay careful attention to and control for sensory and perceptual deficits when conducting cognitive experiments. Evidence from a range of large-scale aging studies has demonstrated that a significant proportion of the age-related variance in several cognitive tasks can be accounted for by hearing and vision loss and that once these sensory differences are statistically controlled, there are no longer age differences in cognitive functioning [ 45]. Baltes and Lindenberger [ 45] proposed that overall neural degeneration may account for both sensory and cognitive deficits - what has been called the common cause hypothesis. Alternative explanations have also been proposed, however. For example, Schneider and Pichora-Fuller [ 44] suggested that perception and cognition are part of a highly integrated system and draw on a common pool of attentional resources. When parts of this system are stressed, such as when auditory or visual acuity are compromised and are essential to a task, other parts of the system will be negatively affected.

Declining sensory and perceptual abilities have important implications for the everyday lives of older adults. Hearing loss can isolate older people, preventing them from engaging in conversation and other social interactions. Visual impairments can limit mobility and interact with attentional deficits to make driving a particularly hazardous activity. As older people develop strategies to compensate for declining sensory abilities, the ways in which they perform other cognitive tasks may also be altered and may be less efficient. Retraining and practice on these tasks may help the adjustment and improve performance.

A. Speech and Language

Speech and language processing are largely intact in older adults under normal conditions, although processing time may be somewhat slower than in young adults. In fact, there is evidence that discourse skills actually improve with age. Older people often tell well-structured elaborate narratives that are judged by others to be more interesting than those told by young [ 46]. They usually have more extensive vocabularies; and although they exhibit the occasional word-finding difficulty, older adults are easily able to provide circumlocutions to mask the problem. They are skilled conversationalists and appear to have few difficulties in processing ongoing speech. As noted above, however, some older adults have hearing loss and so, in conversational settings, may be required to interpret a weak or distorted acoustic signal. Even under these conditions, older people seem able to maintain good levels of comprehension by effectively using context to interpret the message [ 47]. Nevertheless, this compensatory top-down processing may have negative consequences for other cognitive operations and may be at least partly responsible for reducing the functional capacity of working memory. The converse relation has also been proposed, however, namely that the well-documented reduced working memory capacity in older adults limits the comprehension of syntactically complex text. The fact that comprehension of text is often measured by recall, a cognitive function known to be impaired in aging, complicates still further the interpretation of comprehension deficits. Older adults also experience problems with comprehension when individual words are presented at a very rapid rate, but they show sharply reduced impairments when such words form meaningful sentences. Here also, older people seem able to engage intact top-down processes to bolster deficiencies in bottom-up processing. They thus appear to retain good language skills well into older age. Deficits that occur under difficult processing conditions seem primarily attributable to sensory loss or working memory limitations, not to impairments in basic language capacities per se (for a comprehensive review, see [ 48]).

B. Decision Making

Relatively little research has been done on the effects of aging on decision-making. Most of the work has highlighted the potential impact of attentional and working memory limitations on the ability to make decisions, but also has incorporated ideas involving motivation, relevance, emotional investment, and prior knowledge as important moderators of those effects, particularly in real-life contexts. Decision-making seems to be a domain that makes clear demands on processing resources, but in everyday life those demands may be reduced by life-relevant knowledge or expertise in the problem-solving domain. For example, research has shown that when making decisions about healthcare alternatives, buying a car, or buying insurance, older adults often come to the same kinds of decisions as younger adults but reach their conclusions in a different way. They tend to rely more on prior knowledge about the problem domain and less on new information, whereas young people, who likely have less knowledge about these issues, tend to sample and evaluate more current information and consider more alternatives before making their decisions (for review, see [ 49]).

Older adults, again possibly because of working memory limitations, tend to rely on expert opinion to a greater degree than young adults. Although this strategy may work reasonably well when the expert is well-qualified (e.g., a physician for medical decisions), it may leave older people susceptible to things such as investment scams. Poor decision-making may also be a result of episodic memory decline, particularly the loss of memory for details or source. For example, remembering that "Stock ABC is a good investment," without remembering where one heard such information, could lead to a bad decision.

C. Executive Control

In the past decade, there has been an increasing focus on executive control as a primary contributor to cognitive decline with age. Executive control is a multi-component construct that consists of a range of different processes that are involved in the planning, organization, coordination, implementation, and evaluation of many of our nonroutine activities. This so-called central executive [ 14, 50] plays a key role in virtually all aspects of cognition, allocating attentional resources among stimuli or tasks, inhibiting distracting or irrelevant information in working memory, formulating strategies for encoding and retrieval, and directing all manner of problem-solving, decision-making, and other goal-directed activities. Executive control is particularly important for novel tasks for which a set of habitual processes is not readily available. Executive function depends critically on prefrontal cortex, which exerts its broad-reaching controlling influence via extensive reciprocal connections with posterior cortical regions. A parsimonious explanation of cognitive aging ascribes a causal role to executive control deficits - what has been called the frontal lobe hypothesis of aging [ 51]. In support of this hypothesis, both structural and functional neuroimaging studies have revealed a preferential decline in older adults in volume and function of prefrontal brain regions [ 52].

# data[].attributes.attachment_link.title
Changes in Cognitive Function in Human Aging

# data[].attributes.attachment_link.description
As people age, they change in a myriad of ways - both biological and psychological. Some of these changes may be for the better, and others are not. This book primarily concerns the normally aging brain, the neuroanatomical and neurophysiological changes that occur with age, and the mechanisms that account for them.

# data[].attributes.headline
Microstructural maturation of the human brain from childhood to adulthood

# data[].attributes.subject
Microstructural maturation of the human brain from childhood to adulthood

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# data[].attributes.body
https://www.liberty.edu/courseapps/book/psychology-201/module-6/section-2-title/article-title-1/

# data[].attributes.body
https://link.springer.com/chapter/10.1007/978-3-319-47143-3_7

# data[].attributes.headline
Continuity of Cognitive Change across Adulthood

# data[].attributes.subject
Continuity of Cognitive Change across Adulthood

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https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4740316/

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