Lifespan trajectory of myelin integrity and maximum motor speed

Bartzokis, George; Lu, Po H.; Tingus, Kathleen; Mendez, Mario F.; Richard, Aurore; Peters, Douglas G.; Oluwadara, Bolanle; Barrall, Katherine A.; Finn, J. Paul; Villablanca, Pablo; Thompson, Paul M.; Mintz, Jim

doi:10.1016/j.neurobiolaging.2008.08.015

« Previous Next »Neurobiology of Aging
Volume 31, Issue 9 , Pages 1554-1562, September 2010

Lifespan trajectory of myelin integrity and maximum motor speed

George Bartzokis
- Department of Psychiatry and Biobehavioral Sciences, The David Geffen School of Medicine at UCLA, Los Angeles, CA 90024, United States
- Laboratory of Neuroimaging, Department of Neurology, Division of Brain Mapping, The David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States
- Greater Los Angeles VA Healthcare System, Department of Psychiatry, West Los Angeles, CA 90073, United States
- Corresponding author at: 300 UCLA Medical Plaza, Suite 2200, Los Angeles, CA 90095-6968, United States. Tel.: +1 310 206 3207; fax: +1 310 268 3266.
Po H. Lu
- Department of Neurology, The David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States
Kathleen Tingus
- Department of Neurology, The David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States
Mario F. Mendez
- Greater Los Angeles VA Healthcare System, Department of Psychiatry, West Los Angeles, CA 90073, United States
- Department of Neurology, The David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States
Aurore Richard
- Department of Psychiatry and Biobehavioral Sciences, The David Geffen School of Medicine at UCLA, Los Angeles, CA 90024, United States
Douglas G. Peters
- Department of Psychiatry and Biobehavioral Sciences, The David Geffen School of Medicine at UCLA, Los Angeles, CA 90024, United States
Bolanle Oluwadara
- Department of Psychiatry and Biobehavioral Sciences, The David Geffen School of Medicine at UCLA, Los Angeles, CA 90024, United States
Katherine A. Barrall
- Greater Los Angeles VA Healthcare System, Department of Psychiatry, West Los Angeles, CA 90073, United States
J. Paul Finn
- Department of Radiology, The David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States
Pablo Villablanca
- Department of Radiology, The David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States
Paul M. Thompson
- Laboratory of Neuroimaging, Department of Neurology, Division of Brain Mapping, The David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States
- Department of Neurology, The David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States
Jim Mintz
- Department of Psychiatry, University of Texas Health Science Center San Antonio, San Antonio, TX 78229, United States

Received 29 February 2008; received in revised form 26 July 2008; accepted 21 August 2008. published online 16 October 2008.

Abstract

Objective

Myelination of the human brain results in roughly quadratic trajectories of myelin content and integrity, reaching a maximum in mid-life and then declining in older age. This trajectory is most evident in vulnerable later myelinating association regions such as frontal lobes and may be the biological substrate for similar trajectories of cognitive processing speed. Speed of movement, such as maximal finger tapping speed (FTS), requires high-frequency action potential (AP) bursts and is associated with myelin integrity. We tested the hypothesis that the age-related trajectory of FTS is related to brain myelin integrity.

Methods

A sensitive in vivo MRI biomarker of myelin integrity (calculated transverse relaxation rates (R₂)) of frontal lobe white matter (FLwm) was measured in a sample of very healthy males (N=72) between 23 and 80 years of age. To assess specificity, R₂ of a contrasting early-myelinating region (splenium of the corpus callosum) was also measured.

Results

FLwm R₂ and FTS measures were significantly correlated (r=.45, p<.0001) with no association noted in the early-myelinating region (splenium). Both FLwm R₂ and FTS had significantly quadratic lifespan trajectories that were virtually indistinguishable and both reached a peak at 39 years of age and declined with an accelerating trajectory thereafter.

Conclusions

The results suggest that in this very healthy male sample, maximum motor speed requiring high-frequency AP burst may depend on brain myelin integrity. To the extent that the FLwm changes assessed by R₂ contribute to an age-related reduction in AP burst frequency, it is possible that other brain functions dependent on AP bursts may also be affected. Non-invasive measures of myelin integrity together with testing of basic measures of processing speed may aid in developing and targeting anti-aging treatments to mitigate age-related functional declines.

Keywords: Age, Processing speed, Motor, White matter, Oligodendrocyte, Breakdown, Cognition, Dementia, Risk, Neurodegeneration, Alzheimer, Onset, Frontal lobe, Treatment, Prevention