Chapter 8: Adult & Aging Brain

One risk of aging is _________________, a decline in cognitive ability that interferes with a person's day-to-day functioning. While aging is inevitable, dementia and disability are not. In fact, neuroscientists believe our brains can remain ________________________ as we age.

dementia relatively healthy

Main types of changes in aging brain

-structural (cortical thinning, grey matter/white matter volume change) -chemical (change in amounts of neurotransmitters and receptors) -neuronal (change in numbers of neurons and synapses)

An adult brain differs from an adolescent brain in many ways. Between childhood and adulthood, a human brain loses gray matter as excess neurons and synapses are pruned away, although the rate of loss slows down by a person's late ______s. At the same time, some brain regions strengthen their connections with each other, and the major nerve tracts become wrapped in insulating myelin, which increases the brain's _______________.

20 white matter

Your brain is one of the most metabolically active organs, demanding around _____ percent of the body's fuel. Its enormous energy requirements might make the brain even more vulnerable than other tissues to the ______________ changes that occur in aging. While the brain's energy demands remain high, its energy supply can no longer keep pace; the brain's ability to take up and use _____________ diminishes and _______________ metabolism declines.

20% metabolic glucose, mitochondrial

Some studies suggest that cognition starts declining as early as the _____s and _____s, while other studies indicate that cognition improves into the ____s or _____s, before declining.

20s and 30s 50s and 60s

Intelligence peaks during early to middle adulthood, roughly ages _____ to _____.

25 to 60

Studies using brain imaging techniques have revealed that total brain volume begins to decline when people are in their _____s or ____s, and starts declining at a greater rate around age _____.

30s and 40s 60

Around age ____, the white matter in the human brain has reached its peak volume.

40

Physical activity might even slow the progression of ___________________ and dementia, and higher levels of physical activity have been linked to improvements in some markers of structural brain health, such as reduced ______________ and less shrinkage in the _________________

Alzheimer's disease cortical thinning, hippocampus

Specific nutrients have been linked to improved cognitive performance and lower rates of dementia. Antioxidants, such as vitamins ___ and ___, _________________, and _________________ have received considerable attention, with observational studies showing that high dietary intake of these compounds is beneficial. However, the results of lifestyle intervention studies using supplements have been more mixed.

C, E, flavonoids, omega-3-fatty acids

_______________— substantially reducing the number of calories eaten without leading to malnutrition— has been linked to improved cognitive health as well as a longer lifespan.

Caloric restriction

Different cognitive abilities have distinctive patterns of maturation. ________________, which includes abilities like solving problems and identifying patterns, peaks around age _____. By contrast, ____________________, which deals with vocabulary and knowledge of facts, increases until about age ____. Some scientists speculate that there is no single age at which ___________________________________________-

Fluid intelligence, 30 Crystallized intelligence, 50 all (or even most) of our cognitive functions are at their peak

______________ dysfunction often occurs in conjunction with the metabolic changes seen in aging. ______________, the brain's resident immune cells, perform many important jobs: ________________, _____________, and _____________. These _____________ responses are protective, but a prolonged inflammatory state is __________________________

Immune Microglia defending against pathogens, cleaning up cellular debris, and helping maintain and remodel synapses. inflammatory harmful to brain health

Observational studies have found that people who follow plant-rich diets such as the ____________________ diet or ____________________________ (________) are less likely to develop cognitive decline and ______________.

Mediterranean Dietary Approaches to Stop Hypertension (DASH) dementia

__________ stimulation and large ______________ networks can also improve cognitive function in aging. In lab studies, mice housed in cognitively stimulating environments with many opportunities for social interaction perform better on learning and memory tests as they age compared to mice housed in standard cages. Much like physical exercise, cognitive stimulation appears to enhance _________________ by increasing __________________ and boosting levels of important _________________.

Mental, social neuroplasticity neurogenesis, neurotrophic factors

Why does the brain age (4)?

Oxidative stress/ DNA damage Immune dysfunction Impaired Protein Recycling Aging of other body systems

The most important brain area to become fully "wired up" in adulthood is the ____________________As a result, ___________________ is less influenced by emotions, rewards, and social influences compared to the adolescent brain

Prefrontal Cortex decision-making

Selective attention

The ability to focus on a particular stimulus and filter out distractions, ex. listening to your friends in a noisy restaurant

Divided attention

The ability to focus on two tasks at the same time, ex. holding a conversation while driving

Dendritic spines

The tiny protuberances that receive chemical signals

______________________ — the ability to hold a piece of information in mind and manipulate it (for example, looking up a phone number and reciting it as you dial) — also declines with age. Some studies suggest that a slow decline starts as early as age _____. Working memory is an example of ______________ intelligence

Working memory 30

Growing evidence shows that _______________ exercise can improve cognitive function and offset some of the declines seen in aging. Numerous studies have found that people who engage in regular physical activity show improved ___________, improved ___________, and a reduced risk of developing _____________.

aerobic learning, memory, dementia

Although neurogenesis was once believed to halt after __________, we now know of two brain regions that continue to add new neurons throughout life: the __________________ and the ________________ of the hippocampus.

birth olfactory bulbs, dentate gyrus

Exercise can also improve _____________ and increase production of ________________ factors that support new neurons and synapses. For humans, starting exercise later in life can be beneficial, but the studies suggest that adopting an exercise program _______________ could yield even more ________________ benefits.

blood flow neurotrophic earlier in life, neuroprotective

Changes in the aging brain occur within the context of other changes throughout the body. Researchers speculate that worsening ______________ health, for example, could contribute to, or even drive, many changes seen in the aging brain.

cardiovascular

Strong evidence now suggests that habits and choices that keep your body healthy also benefit your mind. Poor ________________ health puts a person at increased risk of age-related cognitive impairment.

cardiovascular

The loss of thin dendritic spines could impair neuronal ______________ and contribute to _____________ decline. So far, direct evidence of their role in cognitive decline is lacking, and more studies are needed.

communication cognitive

Pronounced decline in memory and cognitive ability, once thought to be part of normal aging, are now recognized as separate ________________________ in the aging brain. Although the brain loses some neurons as we age, a widespread and profound loss of neurons is not part of _____________________.

disease processes normal aging

Also, the cellular machinery involved in breakdown and recycling processes degrades with age, reducing the __________ of the "_______________" systems.

efficiency, waste removal

Cortical thinning is especially pronounced in the ____________ lobes and parts of the _____________ lobes.

frontal, temporal

The effect of synaptic changes on cognitive decline is believed to be _________________ than the effects of structural and chemical changes.

greater

A growing area of neuroscientific research focuses on understanding "_________________," which includes lifestyle choices, such as ________ and _____________, which support cognitive health throughout life.

healthy aging diet, exercise

Evidence from rodent studies confirms that exercise increases neurogenesis: Older mice allowed to run on a wheel have higher rates of neurogenesis in the __________________ than sedentary mice, and they perform better on learning and memory tests.

hippocampus

Several changes at the level of ________________________ can also contribute to the decreased volume seen in aging brains. The changes in aging are due to _____________ neurons, retraction and decreased complexity of ___________, and loss of ___________. In contrast, the volume loss in adolescence is primarily driven by synaptic pruning and the death of excess cells.

individual neurons shrinking dendrites myelin

Aging is a dynamic, gradual process. While it can be characterized by resilience in both physical and neurological health, too often aging increases the risk of ____________ and ___________.

injury, disease

Subtle changes in cognition are a normal part of the aging process, with ___________________ being the most common.However, while _____________ declines with age, ______________________ remains largely intact.

memory decline declarative memory, non-declarative memory

Every cell in your body contains organelles called __________________, which function a bit like cellular power plants, carrying out chemical reactions that provide energy for cell use. Some of these metabolic reactions produce harmful byproducts called _____________, highly reactive molecules which, if left unchecked, can destroy fats and proteins vital to normal cell function and can damage DNA as well.

mitochondria free radicals

Studies of brain cells have shown that damage to their __________________ DNA accumulates with age. In addition, the brains of people with mild cognitive impairment and _______________ show more signs of oxidative damage than the brains of healthy people. Studies in rodents also link increased oxidative damage to _______________ impairments.

mitochondrial Alzheimer's disease memory

The formation of new _____________ declines with age.

neurons

Exercise exerts its neuroprotective effects in the brain by improving _________________ — the brain's ability to form and reorganize connections between neurons in response to changes in behavior and environment. Scientists also believe that exercise increases _________________ which, in turn, enhances _________________.

neuroplasticity neurogenesis, neuroplasticity

Your body has natural defense mechanisms to neutralize free radicals. Unfortunately, these mechanisms decline with age, leaving aging tissues more vulnerable to __________________ damage by the free radicals.

oxidative

DNA damage that accumulates over a lifetime could contribute to aging processes throughout the brain and body, and DNA damage due to _________________ has received a great deal of attention.

oxidative stress

Cells normally break down and recycle damaged proteins and molecules, using a process that is usually efficient but not __________. Over time, damaged molecules can ___________ in cells and prevent them from functioning normally. Because neurons in the brain are not ___________________ as cells in other parts of the body (for example, bone marrow, intestinal lining, hair follicles), brain cells might be even more vulnerable to this buildup of damaged molecules.

perfect build up replaced as often

Studies suggest that the rate of neurogenesis _______________ with age in mice, but recent human studies suggest a more _______________ decline. It is not yet clear whether neurogenesis appreciably affects cognition in the aging human brain, but mouse studies indicate that strategies that boost neurogenesis can ______________ cognitive function.

plummets, modest enhance

In the ______________ and __________________, scientists have observed alterations in dendrites. With increasing age, the dendrites shrink, their branches become less ________________, and they lose dendritic __________________

prefrontal cortex, hippocampus complex spines

Excessive buildup of abnormal _____________ in the brain contributes to age-related neurodegenerative diseases like __________ and ________________. Buildup of proteins and other cell components can also contribute to cellular degeneration in the __________ brain.

protein Alzheimer's, Parkinson's healthy

Microglia become more _____________ with age, increasing the _______________ response in the brain while also damping production of helpful _______________ molecules. Mouse studies suggest that ___________ microglial activity also contributes to cognitive impairments.

reactive, inflammatory, anti-inflammatory excessive

The amount of neurotransmitters and the number of their _____________ might also decline with age. Several studies have reported that less _____________ is synthesized in the aged brain, and there are fewer receptors to bind the neurotransmitter. Less robust evidence indicates that the amount of _____________ might also decline with age.

receptors dopamine, serotonin

A study in __________________ observed that the aging process targets a certain class of spines called ______________. These small, slender protuberances are also highly ______________ structures, extending and retracting much more rapidly than the larger "______________" class of spines. This has led scientists to speculate that thin spines might be involved in ___________________, which requires a high degree of synaptic ______________.

rhesus monkeys thin spines plastic, mushroom working memory, plasticity

The aging brain also undergoes numerous changes at synapses. Although the synaptic changes are ______________ and subtle.

selective

Certain aspects of attention can also become more difficult as our brains age. Activities requiring ______________ and _____________ attention become more challenging with age

selective, divided

People who perform cognitively-demanding work or engage in stimulating activities such as reading, solving puzzles, or playing a musical instrument have lower rates of cognitive decline with aging. An active ________________ has also been shown to be beneficial for cognition as we age.

social life

Many different theories have been advanced to explain why neurons, and cells in general, age. One possibility is that changes in gene expression play a role. Researchers have found that genes important for _________________ are expressed less in the brains of older people than in the brains of younger adults. The underexpressed genes also showed more signs of ____________.

synaptic plasticity damage

Our cerebral cortex, the wrinkled outer layer of the brain containing neuron cell bodies, ________ as we age. ___________________ follows a pattern similar to volume loss, with some regions of the brain affected more than others.

thins Cortical thinning

Studies of individual brain regions suggest that the volume loss is not ____________ throughout the brain. Some areas appear to shrink _________, and __________, than other areas. The _______________, _______________, and ________________ show the biggest losses, which worsen in advanced age

uniform more, faster prefrontal cortex, cerebellum, hippocampus

Diets rich in _______________, ____________, _______________, and low in __________ and ___________ products, can reduce cardiovascular risk factors linked to cognitive impairment, such as ______________________ and high levels of __________________.

vegetables, fruits, whole grain meat, dairy high blood pressure, LDL cholesterol

The temporal and frontal lobes are among the areas that demonstrate the most pronounced declines in both ________________ and _____________ ___________. These are the areas that took the _______________ to reach maturity. This finding has led to a "________________" theory of brain aging, which holds that the _______ parts of the brain to develop are the _______ to deteriorate.

volume, cortical thickness longest last in, first out last, first

Interestingly, studies of age-related changes in ____________________ support the "last in, first out" hypothesis. The first of the brain's long-distance fibers to develop are the _______________ fibers that connect the ___________ to lower parts of the _______________ and _____________. Fibers connecting diffuse areas within a single hemisphere — _____________ fibers — are the last to reach maturity, and show the ______________ functional declines with age.

white matter projection fibers cortex, brain and spinal cord association steepest

Much of the added white matter represents increased connections between _____________________ brain areas. During childhood and adolescence, most brain networks are ______________ organized, with areas near each other working together to accomplish a cognitive task. In adulthood, the brain's organization is more widely distributed, with distant areas connected and working together.

widely separated locally