Glossary: Alzheimers

Content provided by the Faculty of the Harvard Medical School

Glossary

acetylcholine: A neurotransmitter in the brain that is in low supply in people with Alzheimer's disease.

agnosia: An impairment of sensory perception.

amyloid precursor protein (APP): A normal brain protein that, when fragmented under certain circumstances, produces beta-amyloid.

aphasia: An impairment in the ability to use language.

apolipoprotein E (ApoE): A cholesterol-carrying protein that may be involved in Alzheimer's disease.

apraxia: An impairment in motor skills and coordination.

beta-amyloid: An abnormal protein deposited in the brain in Alzheimer's disease.

catastrophic reaction: Strong emotional reaction to a minor event.

cholinergic neurons: Nerve cells that produce acetylcholine.

Creutzfeldt-Jakob disease: A rare, rapidly progressive dementia caused by an infectious agent known as a prion.

delirium: Mental impairment with altered consciousness.

dementia: Impairment of memory and other cognitive abilities.

dopamine: A neurotransmitter in the brain involved in the regulation of movement.

excitotoxins: Brain chemicals that in excessive amounts can damage neurons.

free radicals: Reactive molecules that can damage tissue.

frontotemporal lobar degeneration: A brain disorder that can cause dementia, aphasia, neurotic behavior, and gradual changes in personality and emotional control.

Huntington's disease: An inherited disorder characterized by involuntary writhing movements and dementia.

infarct: An area of dead or dying tissue caused by lack of circulation.

limbic system: An area of the brain containing the amygdala and hippocampus; involved in memory and emotions.

mild cognitive impairment: A condition in which memory or, less commonly, another cognitive function is below normal but does not interfere with daily functioning. Considered a transitional state between normal forgetfulness and dementia.

neuritic plaques: Clumps of degenerating neuronal axons and dendrites surrounding an amyloid core that are found in Alzheimer's disease.

neurofibrillary tangles: Abnormal twisted fibers inside neurons in Alzheimer's disease.

neurons: Nerve cells, such as those in the brain.

neurotransmitters: Chemicals that transmit nerve impulses from one neuron to another.

normal-pressure hydrocephalus: A condition characterized by an excess of cerebrospinal fluid in the brain; can cause symptoms of dementia, loss of bladder control, and difficulty walking.

Parkinson's disease: A movement disorder resulting from dopamine deficiency; dementia occurs in 15%–20% of cases.

plaques: See neuritic plaques.

prion: The smallest known infectious agent; unlike a virus or bacterium, it's made up entirely of protein and contains no nucleic acid.

serotonin: A neurotransmitter in the brain that's involved in regulating sleep and sensory perception. A lack of serotonin has been linked to depression.

sundowning: The appearance or worsening of behavior problems in the evening.

tangles: See neurofibrillary tangles.

tardive dyskinesia: Involuntary writhing movements of the facial muscles and tongue caused by high doses of antipsychotic drugs over long periods of time.

vascular cognitive impairment: Dementia caused by numerous infarcts, caused by a series of tiny strokes. Also called vascular dementia and multi-infarct dementia.

Last updated:	January 23, 2007