Brain Shrinkage in Old Age and in Alzheimer's Disease
Alzheimer's disease is a degenerative disease of the brain. Because of this the appearance of the brain changes dramatically as the disease progresses.
Alzheimer's disease (AD) most frequently occurs in older people. But even the ‘normal' brain undergoes changes during our lifetime. The brain weighs around 350 grams at birth and increases to around 1,375 grams (about 3 pounds) by the age of 20. In fact the brain quadruples in size in the first three years of life. Then things begin to deteriorate! Brain weight starts to decline between the ages of 45 and 50 years. The brain decreases by about 11 per cent from its maximum weight in early adulthood.
In the older brain tissue loss is most obvious on its surface. There is unmistakable shrinkage in the natural convolutions in brain tissue. Changes are most marked in the forebrain and less so in the cerebellum (the area at the back of the brain mainly responsible for balance and dexterity of movement).
In the young brain the ratio of gray to white matter is 1:28. This declines to around 1:13 in the brains of people in their sixties.
In Alzheimer's disease brain shrinkage is due to the death of neurons (nerve cells). This is caused by two major types of lesion, amyloid plaques and neurofibrillary tangles , that result from abnormal processing of proteins in the brain. The brain's cortex shrinks, the hippocampus area of the cortex is most dramatically affected. The ventricles within the brain enlarge.
For More Information
Click here to see the physical effects of brain damage that occurs with Alzheimer's disease.
Dr David Roeltgen has written a great sharepost called "Learn Your Lobes: An Introduction to the Brain". Click here for his information about what areas are affected by Alzheimer's disease and how this impacts on behavior.