Inside the Brain
A tour of how the mind works
Alzheimer's Changes the Whole Brain
Alzheimer's disease leads to nerve cell death and tissue loss throughout the brain. Over time, the brain shrinks dramatically, affecting nearly all its functions.
These images show:
A brain without the disease.
A brain with advanced Alzheimer's.
How the two brains compare.
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Under the Microscope
Scientists can also see the terrible effects of Alzheimer's disease when they look at brain tissue under the microscope. Scientists are not absolutely sure what causes cell death and tissue loss in the Alzheimer's brain, but the plaques and tangles in the figures below are prime suspects.
Alzheimer's tissue has many fewer nerve cells and synapses than a healthy brain.
Plaques, abnormal clusters of protein fragments, build up between nerve cells.
Dead and dying nerve cells contain tangles, which are made up of twisted strands of another protein.
More About Plaques
Plaques form when protein pieces called beta-amyloid (BAY-tuh AM-uh-loyd) clump together. Beta-amyloid comes from a larger protein found in the fatty membrane surrounding nerve cells.
Beta-amyloid is chemically "sticky" and gradually builds up into plaques.
The most damaging form of beta-amyloid may be groups of a few pieces rather than the plaques themselves. The small clumps may block cell-to-cell signaling at synapses. They may also activate immune system cells that trigger inflammation and devour disabled cells.
More About Tangles
Tangles destroy a vital cell transport system made of proteins. This electron microscope picture shows a cell with some healthy areas and other areas where tangles are forming.
In healthy areas:
- Orderly, parallel strands for delivering key materials to the cells
- A protein called tau helps keep the strands straight
In areas where tangles are forming:
Nutrients and other essential supplies can no longer move through the cells, which eventually die.
- Tau collapses into twisted strands called tangles
- The strands can no longer stay straight and disintegrate
Progression Through the Brain
Plaques and tangles (shown in the blue-shaded areas) tend to spread through the cortex in a predictable pattern as Alzheimer's disease progresses. The rate of progression varies greatly. On average, a person with Alzheimer's lives four to eight years after diagnosis, but can live as long as 20 years, depending on other factors. The course of the disease depends in part on age at diagnosis and whether a person has other health conditions.
Earliest Alzheimer's - changes may begin 20 years or more before diagnosis.
Mild to moderate Alzheimer's stages - generally last from 2 - 10 years.
Severe Alzheimer's - may last from 1 - 5 years.
Earliest Alzheimer's Stages
In the earliest stages, before symptoms can be detected with current tests, plaques and tangles begin to form in brain areas involved in:
Learning and Memory
Thinking and Planning
Mild to Moderate Alzheimer's
In mild to moderate stages, brain regions important in memory and thinking and planning develop more plaques and tangles than were present in early stages. As a result, individuals develop problems with memory or thinking serious enough to interfere with work or social life. They may also get confused and have trouble handling money, expressing themselves and organizing their thoughts. Many people with Alzheimer's are first diagnosed in these stages.
As Alzheimer's progresses, individuals may experience changes in personality and behavior and have trouble recognizing friends and family members.
Plaques and tangles also spread to areas involved in:
Speaking and Understanding Speech
Your sense of where your body is in relation to objects around you
Severe Alzheimer's Disease
In advanced Alzheimer's disease, most of the cortex is seriously damaged. The brain shrinks dramatically due to widespread cell death. Individuals lose their ability to communicate, to recognize family and loved ones and to care for themselves.