Glossary

Acetylcholine: A neurotransmitter that plays a role in concentration, learning and memory by helping brain cells communicate with each other. close window

Acquisition: The first step in memory formation, acquisition is the process of learning new information. close window

Age-Related Cognitive Decline: The slight loss of memory and speed of information processing that occurs with normal aging. close window

Alien limb: A feeling that a limb is not part of one’s body. Sometimes the limb may move on its own in an uncontrollable fashion. close window

Amnesia: A disturbance in the memory of information stored in long-term memory, in contrast to short-term memory, manifested by total or partial inability to recall past experiences. close window

Amygdala: A brain structure anterior to the hippocampus that is involved in emotional processing and formation of long-term memories. close window

Amyloid: A group of abnormal proteins that cause disorders of the brain, heart, kidney, and other organs. Alzheimer's disease is characterized by deposits of a certain form of the beta sub-type of amyloid within the brain. close window

Aphasia: Impaired or absent comprehension or production of, or communication by, speech, writing, or signs, due to an acquired lesion of the dominant cerebral hemisphere. close window

Apraxia: An inability to correctly perform learned skilled movements. close window

Ataxia: Wobbliness. Ataxia is incoordination and unsteadiness due to the brain’s failure to regulate the body’s posture and regulate the strength and direction of limb movements. Ataxia is usually a consequence of disease in the brain, specifically in the cerebellum which lies beneath the back part of the cerebrum. close window

Axon: A long projection from a neuron that transmit signals to other neurons. close window

Basal Ganglia: The basal ganglia are a group of structures deep within the brain involved in voluntary movement, eye movement, and cognition. For a picture and further discussion, see WWAMI Medical Education Program. close window

Caudate and Putamen: The caudate and putamen are structures of the basal ganglia. Taken together, they are called the striatum. The striatum is involved in movement planning. close window

Cerebral Cortex: The outer layer of nerve cells surrounding the cerebrum that carries out all aspects of higher thinking, such as analyzing and organizing information and storing and retrieving memories. close window

Cerebrum: The largest part of the brain; it is responsible for learning and other conscious mental functions. close window

Cholinesterase Inhibitors: These medicines inhibit the dismantling of a neurotransmitter (see glossary) called Acetylcholine, with the result that concentrations of acetylcholine in the brain rise. The enzymes that dismantle acetylcholine are called cholinesterases. Alzheimer's disease is characterized by low levels of acetylcholine in the brain. close window

Chorea: Chorea is the term for the uncontrollable movements of the arms, legs, trunk and face often seen in Huntington’s Disease. close window

Cognitive functions: All of the brain mechanisms involved with thinking, learning and remembering. close window

Compassionate-use basis: Certain US FDA-approved medications may be used outside of their approved application if a physician feels that it may be of potential benefit to a patient. close window

Computed Tomography: Imaging anatomic information from a cross-sectional plane of the body, each image generated by a computer synthesis of x-ray transmission data obtained in many different directions in a given plane. close window

Consolidation: The second step in memory formation, in which the brain transforms temporary memories into long-term ones. close window

Declarative Memory: The conscious or explicit acquisition and recollection of facts and events. close window

Dementia: A progressive decline of mental functions resulting in memory loss and confusion that interfere with a person's routine, daily activities; A group of brain activities that includes short-term memory, planning and staying focused on a task. close window

Dendrites: Small branching parts of a neuron, which receive chemical messages from other neurons and relay them to the body of the neuron. close window

De novo mutation: A mutation that occurs for the first time in the person. affected with the disease. Although this change has not been passed from the affected person's parents, once it occurs, it can be passed to the affected person's children. close window

Dysphagia: Difficulty in swallowing. Dysphagia is due to problems in nerve or muscle control. It is common, for example, after a stroke. Dysphagia compromises nutrition and hydration and may lead to aspiration pneumonia and dehydration. close window

Dystonia: An involuntary, sustained muscle contraction that frequently causes twisting and repetitive movements or abnormal postures. close window

Explicit Memory: One of three classifications of memory, a type of long-term memory involving information retrieval. close window

Extrapyramidal System: That part of the nervous system that regulates subconscious control of skeletal muscle through the basal ganglia. Symptoms that result from impairment of this system include, but are not limited to, weakness, abnormal muscle reflexes, and increased muscle tone. close window

Frontal Lobes: The frontal lobes are the front part of the brain and are involved in planning, organization and initiation of movement. See Centre for Neuro Skills for a picture and more information on the frontal lobes. close window

Gait: How a person walks. close window

Gliosis: Activation of neuroglia in the area of a degenerative lesion. close window

Hashimoto’s Encephalopathy: A neurologic illness in which patients may present with a rapidly progressive dementia often with motor and psychiatric features. Seizures are relatively common. Patients have elevated levels of either anti-thyroglobulin and/or anti-thyroperoxidase (also called anti-TPO or anti-microsomal) antibodies. close window

Hippocampus: A peninsula-shaped structure in the middle of the brain that is crucial for learning as well as for consolidating long-term explicit memories. close window

Huntingtin: The Huntington gene codes for the protein huntingtin, which is present in all humans, with the greatest abundance in the brain and testes. The protein expressed in people with Huntington’s disease is chemically different from the protein in people who do not carry the mutation. close window

Hydrocephalus: A condition in which the cerebral ventricles in the brain are dilated. This occurs most often because of an obstruction in the cerebrospinal fluid pathways. close window

Iatrogenic: Cases acquired as the result of accidental transmission from one patient to another by medical or surgical procedures. close window

Implicit Memory: One of three classifications of memory, it is the information you recall unconsciously in order to do things like tie your shoe, ride a bicycle, or drive a car. It is also known as procedural memory. close window

Long-Term Memory: A memory that lasts several hours or longer. close window

Magnetic Resonance Imaging (MRI): A diagnostic and research tool that uses magnetic fields to help form images of the brain. close window

Mutation: A change in the DNA code producing a disease causing form of a gene. close window

Myoclonus: An involuntary, shock-like movement of a limb or other body part that lasts a second or less. The affected limb may appear as though it is twitching or jumping. close window

Neurodegenerative Disease: A progressive neurological disease leading to loss of a specific population of nerve cells in the brain, spinal cord, or less frequently, peripheral nerves or muscles. Usually these diseases are caused by a genetic mutation in a specific neuronal protein that leads to a loss of function of that protein or slow accumulation of insoluble material in or around the cell. Examples of neurodegenerative diseases include: Huntington’s disease, Parkinson’s disease, Alzheimer's disease, frontotemporal dementia, Creutzfeldt-Jakob disease and spinocerebellar ataxias. close window

Neuron: The morphologic and functional unit of the nervous system, consisting of the nerve cell body, the dendrites, and the axon. close window

Neuropsychology: Specialty of psychology concerned with the study of the relationships between the brain and behavior, including the use of psychological tests and assessment techniques to diagnose specific cognitive and behavioral deficits. close window

Nondeclarative Memory: The nonconscious or implicit ability to express and practice learned information. close window

Neurotransmitters: These are chemical substances used for communication between one nerve cell and the next. There are many neurotransmitters, although there are only a few that are very common and account for a lot of the communication functions in the brain. Some of the most commonly studied neurotransmitters are dopamine, acetylcholine, serotonin, glutamate and norepinephrine, GABA (gamma-amino-butyric acid), glycine. close window

Penetrance: The proportion of individuals with a specific genotype that express the associated phenotype. close window

Pleocytosis: An increased number of white blood cells in a bodily fluid, such as cerebrospinal fluid (CSF), indicative of an inflammatory, infectious, or malignant condition. close window

Polymorphism: A change in the DNA code that does not alter the functioning of a gene and therefore does not cause a disease. Some polymorphisms can confer some susceptibility or resistance to disease. close window

Positron Emission Tomography (PET): An imaging technique that shows changes in blood flow as well as concentrations of oxygen and other substances in brain tissue. close window

Recovered Memory: An occurrence that someone recalls long after it is thought to have taken place. close window

Prodromal Symptoms: Any symptom affecting a system other than the nervous system preceding the first neurologic symptom or sign. close window

Rapidly Progressive Dementia: A dementing illness in which the time course from first symptom to dementia is less than two years, and often less than one year. close window

Retrieval: The act of trying to recall something, the third step in memory formation. Retrieval involves the reactivation of particular nerve-cell pathways that encoded a given piece of information. close window

Schizophrenia: A common type of psychosis, characterized by abnormalities in perception, content of thought, and thought processes (hallucinations and delusions) and by extensive withdrawal of interest from other people and the outside world, with excessive focusing on one's own mental life; now considered a group or spectrum of disorders rather than a single entity, with distinction sometimes made between process schizophrenia and reactive schizophrenia. close window

Semantic Memory: One of three classifications of memory; it involves common knowledge of such things as historical figures, public events, and frequently used words. It is also called general memory. close window

Short-Term Memory: A memory that lasts anywhere from a few seconds to a few hours; it is the kind of memory that is mostly likely to be forgotten several hours or longer. close window

Single Photon Emission Computed Tomography (SPECT): tomographic imaging of metabolic and physiologic functions in tissues; the image being formed by computer synthesis of photons of a single energy emitted by radionucleotides administered in suitable form to the patient. close window

Synapse: The microscopic space between the dendrites of two neurons across which chemical neurotransmitters carry messages from one neuron to the other. close window

Thalamus: A brain structure above the hippocampus which helps with memory consolidation. close window

Trinucleotide codon: DNA is made up of nucleotides abbreviated A,T,G,C. In the Huntington gene there is a series of C-A-G repeats (each one is a tri nucleotide codon). People with the disease have more C-A-G repeats than people without the disease. These C-A-G repeats may possibly lead to neurotoxicity. See the HOPES program at Stanford for further description. close window

Vacuolation: A neuropathologic term that replaces the older terminology of “spongiform change.” This term describes fluid-filled vesicles (vacuoles) that are seen at dendrite terminals in the neuropil. This is considered to be a classic neuropathologic feature of prion diseases. close window