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Myelin breakdown mediates age-related slowing in cognitive processing speed in healthy elderly men

Po H Lu1, Grace J Lee, Todd A Tishler

  • 1Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States. plu@mednet.ucla.edu

Brain and Cognition
|December 1, 2012
PubMed
Abstract

Insights

Myelin breakdown in late-myelinating brain regions significantly slows cognitive processing speed (CPS) in healthy older men. This age-related cognitive decline is linked to myelin integrity in specific brain areas, not others.

Area of Science:

  • Neuroscience
  • Aging Research
  • Cognitive Science

Background:

  • Investigating age-related cognitive decline in healthy elderly men.
  • Focusing on myelin integrity in late-myelinating regions as a potential mediator.
  • Minimizing confounding factors like Alzheimer's disease and cerebrovascular disease.

Purpose of the Study:

  • To test if myelin breakdown in late-myelinating regions mediates age-related slowing of cognitive processing speed (CPS).
  • To examine the role of myelin integrity in specific white matter tracts.
  • To differentiate the impact of aging on different myelination timelines.

Main Methods:

  • Utilized in vivo MRI to measure myelin integrity (R(2)) in late-myelinating white matter (LMWM) and early-myelinating white matter (splenium of the corpus callosum; SWM).
  • Assessed cognitive processing speed (CPS) using the Trail Making Test in 38 healthy elderly men (mean age 66.3).
  • Analyzed correlations and mediation effects between myelin integrity (R(2)) and CPS.

Main Results:

  • A significant correlation was found between LMWM R(2) and CPS (r=.515, p=.0009).
  • No significant association was observed between SWM R(2) and CPS (p=.409).
  • LMWM R(2) significantly mediated the relationship between age and CPS (p=.037), while SWM R(2) did not.

Conclusions:

  • Age-related slowing of CPS in healthy older adults is mediated by myelin breakdown in vulnerable late-myelinating regions.
  • Myelin integrity in early-myelinating regions (splenium) does not appear to mediate this age-related cognitive slowing.
  • Findings highlight the specific vulnerability of late-myelinating white matter to aging processes affecting cognition.

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