The precise cause of Alzheimer's disease is currently unknown. Researchers have many theories as to what might be the cause and what actually happens to the brain, but have been unable to pin point one reason. For those who wish to find out about the latest research on Alzheimer's I recommend Alzheimer Web run by Dr. David Small a prominent Melbourne University researcher in this area. The photos (micrographs) of Alzheimer's disease on this page are from this site.
	Researchers believe that Alzheimer's disease may be the result of one or all of the following: a slow virus an auto immune reaction (the body attacks itself) a biochemical imbalance in the brain By looking at the brains of Alzheimer patients under the microscope, researchers have found that they have abnormal deposits of a protein called "amyloid."
An amyloid plaque.

Amyloid found between the brain cells are called "plaques" and within cells are called "tangles". These can be seen below. Amyloid is not normally found in the brain and it has been found to come from a larger precursor protein. The precursor protein, called APP (Amyloid Precursor Protein) is normally found in the brain, but for some unknown reason is cut, much like one can cut a large piece of string (APP) into two smaller pieces of string. Amyloid is a small piece of APP correctly called "beta A4 amyloid protein." Researchers are currently trying to determine what cuts APP so that they may be able to find a treatment to stop this process.

Studies have shown that this amyloid is neurotoxic (it poisons brain cells) and is the reason why the brain deteriorates. It has also been found that amyloid interferes with normal brain functioning. Especially with the release of a chemical called "acetyl choline". Acetyl choline is one of the chemicals (neurotransmitter) used by the brain to transmit messages between brain cells. When amyloid prevents the production of transmitter it is like cutting all the wires in a computer, all the electronic bits can't talk to each other so the computer doesn't work properly. Researchers are are now trying to find ways to increase the level of acetyl choline in the brain.

Amyloid deposits are especially found in two specific areas of the brain called the "temporal lobe" and the "frontal lobe." This helps us understand some of the symptoms of Alzheimer's disease. The temporal lobe is involved in storing memory so damage to the temporal lobe causes the memory loss of Alzheimer's disease. The frontal lobe is involved in personality, thus damage to it can result in a change in personality.

Many other new theories keep appearing from research such as; Alzheimer's disease being related to previous head injury, aluminium toxicity in food and even poor dietary intake of vitamin E and zinc. None of these theories have been exclusively proven as yet.

Amyloid Plaques seen in the brain of a patient who has died of Alzheimer's disease.

Neurofibrillary tangles, a second feature of the Alzheimer's brain.

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5 Sep 1997 : M. Lograsso (michael@scientist.com), V. Rane, C. Feeney, T. Stark.