What Happens in the Brain of an Alzheimer's Patient?

What happens in the brain of Alzheimer's patient to cause all of the cognitive and behavioral symptoms of the sickness? Alois Alzheimer was the first to find the strange plaques and tangles; characteristics of sickness in the brain of one of his patient during an autopsy. For years, Alzheimer's disease could only be diagnosed with a high degree of accurate post-mortem. Now researchers are learning more about what exactly is happening in the brain of Alzheimer's patient to cause sickness.

The brains of Alzheimer's patient contain neurofibrillary tangles inside neurons and clumps of fibers called neurotic plaques outside of neurons. These tangles and plaques, first described by Alois Alzheimer in 1907, are the main cause of Alzheimer disease. Brain damage occurs as a result of neurons being clogged with microscopic filaments, which are made up of an abnormal type of Tau protein. Clogged neurons are no longer able to do their job and pass along the impulses they receive from the environment. Therefore, disabled neurons are one cause of cognitive impairments associated with Alzheimer's disease. Brain damage due to neurofibrillary tangles is also found in associated disease such as Parkinson's disease.

However, tangles and plaques are not unique for the development and progression of Alzheimer. Studies now indicate that dementia in Alzheimer's patient is caused by the shrinkage and death of neurons and synaptic loss, not by tangles and plaques themselves. However, according to a leading hypothesis, amyloid deposits play an early role by setting in motion a cascade of biochemical events that cause the cells to shrink and die.

Experts also believe that decreased levels of the neurotransmitter acetylcholine, a chemical that bridges synapses between neurons that effect memory, also contributes to memory loss of Alzheimer's disease.