As the brain ages there are significant changes. The most obvious change is the decrease in weight and volume . For example, the male brain my lose about 80 gm of weight between ages 21 and 55 . By 86 the loss is about 140 gm. compared with young adult (19-21) weight. Some of the structural changes in the aging occur in the frontal lobes, putamen and thalamus They include some thinning of the cortex, decreases in the number of neurons; decrease in synapses; loss of subcortical volume; swelling and break down of myelin sheaths of some glial cells . Before 70, the formation of new synapses keeps the brain functioning almost normally in the elderly. However, after 70 there is significant increase in the loss of neurons and synapses ; This is an effect probably related to the known neurotoxicity of calcium.
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The structural changes that take place in the brains of the aged (70+) are at first compensated for by the formation of new synapses. However, by 85, changes in cerebral cortex, putamen, and thalamus may result in significant neural functional deficits.; Some skills that may be significantly affected are reaction time; decision making; speed of perception; spatial ability and working memory. Later, verbal fluency and mathematical ability decline. Finally, the ability to learn from experiences is impacted. These changes can be hastened and worsened by drugs, poor nutrition, hormone imbalances, dehydration, alcohol, brain injury and depression.