Adult and Aging Brain - Chapter 8 Important Topics

cognitive control

The ability to suppress impulses in favor of more appropriate responses; it depends on the prefrontal cortex and is better "wired up" in adult brains than in adolescent brains where decision-making is more influenced by emotions and rewards and social influences.

fluid intelligence

Abilities such as solving problems and identifying patterns that depend on rapid processing of new information rather than stored knowledge; it peaks around age 30 and includes working memory and processing speed.

crystallized intelligence

Intelligence that deals with vocabulary and knowledge of facts; it increases until about age 50.

normal and pathological aging

Normal aging involves subtle changes in brain structure and chemistry and function that commonly begin in midlife; pronounced declines in memory and cognition once thought normal are now recognized as separate disease processes and widespread profound neuron loss is not part of normal aging.

selective attention

The ability to focus on a particular stimulus and filter out distractions such as friends' voices in a noisy restaurant; it becomes harder with age.

divided attention

The ability to focus on two tasks at the same time such as holding a conversation while driving; it becomes more challenging with age.

age-related volume loss

Total brain volume begins to decline in the 30s or 40s and declines faster around age 60 with the biggest losses in the prefrontal cortex and cerebellum and hippocampus; in aging it comes from shrinking neurons and retracting dendrites and loss of myelin while in adolescence it comes from synaptic pruning and the death of excess cells.

cortical thinning

The thinning of the cerebral cortex with age; it follows a pattern similar to volume loss and is especially pronounced in the frontal lobes and parts of the temporal lobes.

"last in first out" theory

The theory that the last parts of the brain to develop are the first to deteriorate; studies of age-related changes in white matter support it.

projection fibers

The first long-distance white matter fibers to develop; they connect the cortex to lower parts of the brain and spinal cord.

association fibers

Fibers connecting diffuse areas within a single hemisphere; they are the last to reach maturity and show the steepest functional declines with age.

dendritic spines

Tiny protuberances on dendrites that receive chemical signals; with age dendrites shrink and their branches become less complex and spines are lost.

thin spines and mushroom spines

Two classes of dendritic spines; thin spines are small and slender and highly plastic and extend and retract much more rapidly than the larger mushroom spines; aging targets thin spines which may be involved in working memory but direct evidence of their role in cognitive decline is lacking.

free radicals

Highly reactive molecules produced as harmful byproducts of some metabolic reactions in mitochondria; if left unchecked they can destroy fats and proteins vital to normal cell function and can damage DNA.

metabolic changes in aging

The brain is one of the most metabolically active organs and demands around 20 percent of the body's fuel; with age its ability to take up and use glucose diminishes and mitochondrial metabolism declines even though its energy demands remain high.

immune dysfunction

Changes in which microglia (the brain's resident immune cells) become more reactive with age; they increase the inflammatory response while damping production of helpful anti-inflammatory molecules and a prolonged inflammatory state is harmful to brain health.

impaired protein recycling

With age the cellular machinery that breaks down and recycles damaged proteins and molecules becomes less efficient so damaged molecules build up in cells; brain cells may be especially vulnerable because neurons are not replaced as often as other cells.

healthy aging

A growing area of neuroscience research on lifestyle choices such as diet and exercise that support cognitive health throughout life.

Mediterranean diet and DASH diet

Plant-rich diets (DASH stands for Dietary Approaches to Stop Hypertension) linked in observational studies to a lower likelihood of cognitive decline and dementia because they reduce cardiovascular risk factors such as high blood pressure and high LDL cholesterol.

caloric restriction

Substantially reducing the number of calories eaten without leading to malnutrition; it has been linked to improved cognitive health as well as a longer lifespan.

aerobic exercise

Exercise that improves cognitive function and offsets some declines of aging; it improves neuroplasticity and increases neurogenesis and blood flow and production of neurotrophic factors and is linked to reduced cortical thinning and less shrinkage in the hippocampus.

mental stimulation and social networks

Cognitively demanding work and activities such as reading and puzzles and playing a musical instrument and an active social life are linked to lower rates of cognitive decline; they appear to enhance neuroplasticity by increasing neurogenesis and boosting neurotrophic factors.

gray matter

Portions of the brain that look gray because they are composed mainly of neural cell bodies rather than myelinated fibers; it includes the cerebral cortex and subcortical structures and the brain loses some of it between childhood and adulthood as excess neurons and synapses are pruned away.

white matter

The part of the brain that contains myelinated nerve fibers and gets its color from myelin; it increases as major nerve tracts become wrapped in myelin and reaches its peak volume around age 40.

dementia

A decline in cognitive ability that interferes with a person's day-to-day functioning; it is a risk of aging but not an inevitable part of it.

mitochondria

Organelles that function like cellular power plants and carry out chemical reactions that provide energy for the cell; some of these reactions produce harmful free radicals and damage to mitochondrial DNA accumulates with age.

Alzheimer's disease

A major cause of dementia in the elderly and a neurodegenerative disorder marked by the death of neurons in the hippocampus and cerebral cortex and other regions; the brains of affected people show more signs of oxidative damage than those of healthy people.