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Cited by 577Neurogenesis and neuroplasticity mechanismsNeurological Disease Mechanisms and TreatmentsNeuroinflammation and Neurodegeneration Mechanisms

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

Peters, Alan·2002·Journal of Neurocytology
DOI 10.1023/a:1025731309829
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Abstract

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

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  • Electron microscopy studies of non-human primate brain aging have revealed major alterations specifically in the white matter, particularly in the disruption of the myelin sheath.

    “Electron microscopy studies of non-human primate brain aging have revealed major alterations specifically in the white matter, particularly in the disruption of the myelin sheath.51”

    From Molecular and spatial signatures of mouse brain aging at single-cell resolution (2023) · cites this paper as [51]

  • Aging is associated with axonal degeneration characterized by accumulation of organelles and increase of neurofilaments in axoplasm, myelin splitting and degeneration, increase of cellular debris, and proliferation and activation of glial cells.

    “For example, aging is associated with axonal degeneration characterized by accumulation of organelles and increase of neurofilaments in axoplasm, myelin splitting and degeneration, increase of cellular debris, and proliferation and activation of glial cells (Peters, 2003).”

    From NODDI in clinical research (2020) · cites this paper as Peters, 2003

  • Some vacuoles resemble 'myelin balloons,' which are fluid-containing myelin structures observed in aged animals and believed to result from degenerating axons.

    “By EM, some of these vacuoles (Fig. 6, labeled “v”) resemble “myelin balloons,” which are fluid-containing myelin structures observed in aged animals and believed to result from degenerating axons (48).”

    From Microglia depletion exacerbates demyelination and impairs remyelination in a neurotropic coronavirus infection (2020) · cites this paper as [48]

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Authors
Peters, A.
Affiliations
Boston University (US)
Corresponding author
Peters, Alan
ORCID
Peters, Alan
Venue
Journal of Neurocytology
Publisher
Springer Science and Business Media LLC
Published
2002-09
Volume
31
Issue
8-9
Pages
581-593
ISSN
  • 0300-4864 (ISSN-L)
  • 1573-7381
DOI
10.1023/a:1025731309829
OpenAlex
W2126587429
Cited by
577
References
71
Citations by year
2026: 14 · 2025: 32 · 2024: 36 · 2023: 26 · 2022: 43 · 2021: 36 · 2020: 34 · 2019: 29 · 2018: 27 · 2017: 18 · 2016: 24 · 2015: 23 · 2014: 27 · 2013: 19 · 2012: 22
FWCI
0.43
Type
journal article
Language
en
Open access
closed
Licence
Locations
  • Journal of Neurocytology (publishedVersion)
  • PubMed (publishedVersion)
Funders
National Institute on Aging (1PO AG 00001)
Topics
  • Life Sciences › Neuroscience › Developmental Neuroscience › Neurogenesis and neuroplasticity mechanisms
  • Life Sciences › Neuroscience › Neurology › Neurological Disease Mechanisms and Treatments
  • Life Sciences › Neuroscience › Neurology › Neuroinflammation and Neurodegeneration Mechanisms
Keywords
normal aging, myelin degeneration, nerve fiber loss, white matter, cognitive decline, conduction velocity, oligodendrocytes, microglial phagocytosis, optic nerve, anterior commissure, cortical neurons
MeSH terms
Aging, Animals, Cognition Disorders, Gliosis, Humans, Myelin Sheath, Nerve Degeneration, Nerve Fibers, Myelinated, Neural Conduction, Oligodendroglia

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