Age-related slowing in cognitive processing speed is associated with myelin integrity in a very healthy elderly sample

Abstract

Performance on measures of cognitive processing speed (CPS) slows with age, but the biological basis associated with this cognitive phenomenon remains incompletely understood. We assessed the hypothesis that the age-related slowing in CPS is associated with myelin breakdown in late-myelinating regions in a very healthy elderly population. An in vivo magnetic resonance imaging (MRI) biomarker of myelin integrity was obtained from the prefrontal lobe white matter and the genu of the corpus callosum for 152 healthy elderly adults. These regions myelinate later in brain development and are more vulnerable to breakdown due to the effects of normal aging. To evaluate regional specificity, we also assessed the splenium of the corpus callosum as a comparison region, which myelinates early in development and primarily contains axons involved in visual processing. The measure of myelin integrity was significantly correlated with CPS in highly vulnerable late-myelinating regions but not in the splenium. These results have implications for the neurobiology of the cognitive changes associated with brain aging.

Keywords:

• Healthy aging
• Cognition
• Information processing speed
• Myelin
• White matter
• Magnetic resonance imaging
• Alzheimer's disease
• Dementia

Acknowledgments

This work was supported by Grant K23–AG028727 from the National Institute of Aging (NIA), a grant from the Alzheimer's Association (NIRG–07–60424), National Institutes of Health (NIH) grants (MH 0266029; AG027342), the Alzheimer's Disease Research Center Grant P50 AG–16570, and the California Alzheimer's Disease Centers. Additional support for the study came from the Risk Control Strategies Inc. (RCS) Alzheimer's Foundation and the Department of Veterans Affairs.

Disclosures: The authors have nothing to disclose.