The effects of normal aging on myelin and nerve fibers: A review

摘要: It was believed that the cause of cognitive decline exhibited by human and non-human primates during normal aging a loss cortical neurons. is now known significant numbers neurons are not lost other bases for have been sought. One contributing factor may be changes in nerve fibers. With age some myelin sheaths exhibit degenerative changes, such as formation splits containing electron dense cytoplasm, on balloons. suggested lead to because they conduction velocity, resulting disruption timing neuronal circuits. Yet degeneration occurs, redundant increasing thickness suggest sheaths, continuing aging. Another indication this oligodendrocytes increase number with age. In addition stereological studies shown fibers from white matter cerebral hemispheres humans, while optic nerves anterior commissure monkeys. likely fiber also contributes decline, consequent decrease connections between Degeneration itself does seem result microglial cells undertaking phagocytosis. These probably only activated when large lost, can occur nerve.