A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A

Alzheimer's disease (AD)
A progressive degenerative disease of the brain that causes impairment of memory and other cognitive abilities.
Amyloid precursor protein (APP)
The larger protein from which beta-amyloid is formed.
ApoE gene
A gene that codes for a protein that carries cholesterol to and within cells; different forms of the ApoE gene are associated with differing risks for late-onset Alzheimer's disease. This gene may be referred to as a risk factor gene or a "susceptibility gene" because one form of the gene, called APOE4, is associated with the risk of developing late onset AD.
Amnestic
Characterized by memory problems; amnestic MCI is a subtype in which memory problems are the most important feature.
Aricept® (Donepezil)
One of a group of drugs called cholinesterase inhibitors approved by the U.S. Food and Drug Administration to treat the symptoms of Alzheimer's disease. Other approved drugs of the type commonly being prescribed are Razadyne® (galantamine) and Exelon® (rivastigmine). Another medication called Namenda® (mementine) is a different type of drug, an N-methyl D-asparate (NMDA) antagonist, and is prescribed to delay some of the symptoms of moderate to severe Alzheimer's disease.
Assisted Living
Facilities for adults who need help with everyday tasks such as dressing, eating, bathing, or using the bathroom, but who don't require full-time nursing care. Some facilities have special units for memory-impaired residents. Health insurance often does not cover these types of facilities, but long-term care insurance may.
Axon
The extension from a neuron that transmits outgoing signals to other neurons.
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B

Beta-amyloid
Derived from the amyloid precursor protein and found in plaques, the insoluble deposits outside neurons. May also be called A-beta.
Beta-amyloid plaque
A largely insoluble deposit found in the space between nerve cells in the brain. The plaques in Alzheimer's disease are made of beta-amyloid and other molecules, surrounded by non-nerve cells (glia) and damaged axons and dendrites from nearby neurons.
Biomarkers
Blood-brain barrier
A barrier that prevents most large molecules, red and white blood cells, and disease-causing organisms (such as bacteria) in the bloodstream from moving into the brain. The barrier is formed by a type of glial cell aided by tight junctions that act like little "spot welds" between adjacent endothelial cells that constitute the lining of brain blood vessels.
Brain-derived neurotrophic factor (BDNF)
A growth factor that stimulates survival, growth, and adaptability of some neurons. Increased levels in some brain regions are related to physical exercise, in animal experiments.
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C

Capillaries
Billions of tiny blood vessels in the brain that carry oxygen, glucose (the brain's principal source of energy), nutrients, and hormones like insulin to brain cells so they can do their work, and remove carbon dioxide and cell waste products.
Cerebral cortex
The outermost layer of the cerebral hemispheres sometimes referred to as the gray matter. It is composed of neurons and nerve fibers and associated support cells called glia.
Cerebrospinal fluid (CSF)
The fluid found in and around the brain and spinal cord. Its function is to transport substances to and away from the brain itself and to cushion the brain hydraulically. Measuring cerebrospinal fluid and its contents helps scientists understand chemistry of the brain. CSF is collected by a procedure called lumbar puncture.
Cholesterol
Chromosomes
Thread-like structures in the nucleus of a cell that contain the DNA. Sequences of DNA make up genes. Most human cells have twenty-three pairs of chromosomes containing a total of approximately thirty thousand genes.
Clinical trial
A research study involving humans; these studies rigorously test the safety, side effects, and the effectiveness of a medication or behavioral treatment.
Cognition
Conscious thought and mental activity, including learning, perceiving, making decisions, and remembering.
Cognitive reserve
The brain's ability to operate effectively even when some damage to cells or brain cell communications has occurred.
Computed tomography (CT) scan
A diagnostic procedure that uses special X-ray equipment and computers to create cross-sectional pictures of the body.
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D

Delusion
An abnormal mental state characterized by false beliefs that persist despite the facts. People with Alzheimer's may experience delusions that cause them to feel suspicious or paranoid.
Dementia
A broad term referring to a decline in cognitive function that interferes with daily life and activities. Alzheimer's disease is one form of dementia.
Dendrite
A branch-like extension of a neuron that receives messages from other neurons.
Diabetes
Chronic metabolic disorder in which the body doesn't produce or properly use insulin, a hormone that is made in the pancreas and is essential for the healthy functioning of all cells in the body.
Disease-modifying drug
DNA (deoxyribonucleic acid)
DNA forms two long, intertwined, thread-like strands called chromosomes. Each cell has 46 chromosomes in 23 pairs, which are found in the nucleus. The DNA in chromosomes is made up of four chemicals, or bases, strung together in various sequence patterns. The DNA in nearly all cells of an individual is identical. Each chromosome contains many thousands of segments, called genes.
Dominant and recessive genes
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E

Early-onset Alzheimer's disease
A rare form of AD that usually affects people between ages thirty and sixty. It is called familial AD (FAD) if it runs in the family.
Entorhinal cortex
An area within the brain where damage from AD often begins.
Epidemiological study
A study of the causes, distribution, and control of disease in populations, with emphasis on investigating relationships between personal characteristics (demographic, socioeconomic, lifestyle, biological and genetic) and occurrence of disease.
Enzyme
A protein that causes or speeds up a biochemical reaction.
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F

Free radical
A highly reactive molecule (typically oxygen or nitrogen) that combines easily with other molecules because it contains an unpaired electron. The combination with other molecules sometimes damages cells.
Functional MRI (fMRI)
An adaptation of an MRI (see magnetic resonance imaging) technique that measures brain activity during a mental task, such as one involving memory, language, or attention.
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G

Genetic risk factor
A variant in a cell's DNA that does not cause a disease by itself but may increase the chance that a person will develop a disease.
Genome-wide association study
Glial cell
A type of brain cell that supports, protects, or nourishes neurons. One form of glia are called microglia and they appear to be part of an inflammatory response that helps the brain clear accumulating beta amyloid.
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H

Hallucination
A false perception experienced by some people with Alzheimer's, in which they see, hear, smell, taste and/or feel something that isn't there.
Hippocampal formation
A structure in the brain that plays a major role in learning and memory and is involved in converting short-term to long-term memory. Also called the hippocampus.
Hospice Care
End-of-life care focused on providing comfort and support rather than curing disease, and which is provided by health professionals and volunteers. Hospice care can take place at home, at a hospice center, in a hospital or in a skilled nursing facility. Medicare provides a hospice benefit.
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I

Inflammation
The process by which the body responds to cellular injury by attempting to eliminate foreign matter and damaged tissue.
Insulin resistance
A condition in which the pancreas makes enough insulin, but the cells do not respond properly to it; characterizes and precedes type 2 diabetes.
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L

Late-onset Alzheimer's disease
The most common form of AD. It occurs in people aged sixty and older.
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M

Magnetic resonance imaging (MRI)
A diagnostic and research technique that uses magnetic fields to generate a computer image of internal structures in the body.
Memory
Metabolism
All the chemical processes that take place inside the body. In some metabolic reactions, complex molecules are broken down to release energy. In others, the cells use energy to make complex compounds out of simpler ones (like making proteins from amino acids).
Microtubule
An internal support structure for cells including a neuron that guides organelles and molecules from the body of the cell to the end of the axon.
Microglia
Mild cognitive impairment (MCI)
A condition in which a person has cognitive problems greater than those expected for his or her age. Amnestic MCI includes memory problems, but not the personality or other cognitive problems that characterize AD.
Mutation
A permanent change in the DNA of a cell that can affect the structure of a protein to such an extent that it causes a disease.
Myelin
Whitish layers of compacted glial cell membranes that surround and insulate an axon, allowing the axon to transmit electrical messages more rapidly from the cell body to the synapse.
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N

Neurodegenerative disease
A disease characterized by a progressive decline in the structure and function of brain tissue. These diseases include AD, Parkinson's disease, frontotemporal lobar degeneration, and dementia with Lewy bodies. They are usually more common in older people.
Neurofibrillary tangle
A collection of twisted and hyperphosphorylated tau found in the cell body, axons, and dendrites of a neuron in AD.
Neurologist
A physician trained in diagnosing and treating diseases of the nervous system, including diseases of the brain, spinal cord, nerves and muscles.
Neuron
A nerve cell.
Neurotransmitter
A chemical messenger between neurons. These substances are released by the axon of one neuron and excite or inhibit activity in a neighboring neuron.
Nonamnestic
Not characterized by memory problems; nonamnestic MCI is characterized by declines in other cognitive skills, and is not thought to be an early stage of Alzheimer's disease.
Normal Aging
Nucleus
The structure within a cell that contains the chromosomes and controls many of the cell's activities.
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O

Oligomers
Clusters of a small number of beta-amyloid peptides.
Oxidative damage
Damage that can occur to cells when they are exposed to too many free radicals.
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P

Pathology
Structural and functional changes to cells and tissues of the body that result from a disease process.
Pathology of Alzheimer's disease
Pittsburgh Compound B (PiB)
The radioactive tracer compound used during a PET (see Positron Emission Tomography) scan of the brain to show beta-amyloid deposits.
Positron Emission Tomography (PET)
An imaging technique using radioisotopes that allows researchers to observe and measure activity in different parts of the brain by monitoring blood flow and concentrations of substances such as oxygen and glucose, as well as other specific constituents of brain tissues.
Protein-misfolding disease
Proteins
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S

Sundowning
Behavioral problems such as restlessness, agitation, and irritability that occur in people with dementia typically at the end of the day and sometimes into the night. Doctors are not certain what causes sundowning, but it can be troubling for caregivers.
Support Group
A group that provides members with information and assistance by sharing experiences and concerns, and factual information. Some are moderated by health professionals, while others have peer leaders. Caregivers often find support groups helpful, and they may meet in person or sometimes online. There are now groups to address the special issues of people who are diagnosed at the earliest stages of Alzheimer's disease.
Susceptibility Genes
See genetic risk factor.
Synapse
The tiny gap between nerve cells across which neurotransmitters and nerve signals pass.
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T

Tau
A protein that helps to maintain the structure of microtubules in normal nerve cells. Abnormal tau is a principal component of the paired helical filaments in neurofibrillary tangles.
Transgenic
An animal that has had a gene (such as the human APP gene) inserted into its chromosomes for the purpose of research. Mice carrying a mutated human APP gene often develop plaques in their brains as they age.
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Alzheimer's Disease (AD)

A progressive degenerative disease of the brain that causes impairment of memory and other cognitive abilities.

Amyloid Precursor Protein (APP)

The larger protein from which beta-amyloid is formed.

ApoE Gene

A gene that codes for a protein that carries cholesterol to and within cells; different forms of the ApoE gene are associated with differing risks for late-onset Alzheimer's disease. This gene may be referred to as a risk factor gene or a "susceptibility gene" because one form of the gene, called APOE4, is associated with the risk of developing late onset AD.

Beta-Amyloid

Derived from the amyloid precursor protein and found in plaques, the insoluble deposits outside neurons. May also be called A-beta.

Beta-Amyloid Plaque

A largely insoluble deposit found in the space between nerve cells in the brain. The plaques in Alzheimer's disease are made of beta-amyloid and other molecules, surrounded by non-nerve cells (glia) and damaged axons and dendrites from nearby neurons.

Cognitive Reserve

The brain's ability to operate effectively even when some damage to cells or brain cell communications has occurred.

Dementia

A broad term referring to a decline in cognitive function that interferes with daily life and activities. Alzheimer's disease is one form of dementia.

Functional MRI (fMRI)

An adaptation of an MRI (see magnetic resonance imaging) technique that measures brain activity during a mental task, such as one involving memory, language, or attention.

Hippocampal Formation

A structure in the brain that plays a major role in learning and memory and is involved in converting short-term to long-term memory. Also called the hippocampus.

Inflammation

The process by which the body responds to cellular injury by attempting to eliminate foreign matter and damaged tissue.

Insulin Resistance

A condition in which the pancreas makes enough insulin, but the cells do not respond properly to it; characterizes and precedes type 2 diabetes.

Magnetic Resonance Imaging (MRI)

A diagnostic and research technique that uses magnetic fields to generate a computer image of internal structures in the body.

Mild Cognitive Impairment (MCI)

A condition in which a person has cognitive problems greater than those expected for his or her age. Amnestic MCI includes memory problems, but not the personality or other cognitive problems that characterize AD.

Neurodegenerative Disease

A disease characterized by a progressive decline in the structure and function of brain tissue. These diseases include AD, Parkinson's disease, frontotemporal lobar degeneration, and dementia with Lewy bodies. They are usually more common in older people.

Oligomers

Clusters of a small number of beta-amyloid peptides.

Oxidative Damage

Damage that can occur to cells when they are exposed to too many free radicals.

Pittsburgh Compound B (PiB)

The radioactive tracer compound used during a PET (see Positron Emission Tomography) scan of the brain to show beta-amyloid deposits.

Pittsburgh Compound B (PiB)

The radioactive tracer compound used during a PET (see Positron Emission Tomography) scan of the brain to show beta-amyloid deposits.

Synapse

The tiny gap between nerve cells across which neurotransmitters and nerve signals pass.

Tau

A protein that helps to maintain the structure of microtubules in normal nerve cells. Abnormal tau is a principal component of the paired helical filaments in neurofibrillary tangles.

Tangles

A protein that helps to maintain the structure of microtubules in normal nerve cells. Abnormal tau is a principal component of the paired helical filaments in neurofibrillary tangles.

Memory

Normal Aging

Genetic Risk Factor

Dominant and Recessive Genes

Genes and Proteins

Protein-Misfolding Disease

Cholesterol

Biomarkers

Disease-Modifying Drug

Transgenic Mice

An animal that has had a gene (such as the human APP gene) inserted into its chromosomes for the purpose of research. Mice carrying a mutated human APP gene often develop plaques in their brains as they age.

Pathology

Microglia

Insulin & Insulin Resistance

Susceptibility Gene

A variant in a cell's DNA that does not cause a disease by itself but may increase the chance that a person will develop a disease.

Susceptibility Genes

A variant in a cell's DNA that does not cause a disease by itself but may increase the chance that a person will develop a disease.

Genome-Wide Association Study

Vascular Disease

Genetics

Genetics

Normal Aging