Slow decay of myelin in brain causes ageing symptoms

October 18th, 2008 - 1:31 pm ICT by IANS  

Washington, Oct 18 (IANS) Middle age is the time when people begin to lose myelin, the fatty sheath of “insulation” that coats our nerve cells and allows quicker responses. George Bartzokis, professor at the Semel Institute for Neuroscience and Human Behaviour, University of California - Los Angeles (UCLA) and his colleagues compared how quickly a group of males aged between 23 and 80 years could perform a task and then correlated their performances with their brains’ myelin integrity.

The researchers found a striking correlation between the speed of the task and the integrity of myelination over the range of ages. Put another way, after middle age, we start to lose the battle to repair the myelin in our brain, and our motor and cognitive functions begin a long, slow downhill slide.

The myelination of brain circuits follows an inverted U-shaped trajectory, peaking in middle age. Bartzokis and others have long argued that brain ageing may be primarily related to the process of myelin breakdown, according to an UCLA press release. The findings have been reported online in Neurobiology of Aging.

“Studies have shown us that as we age, myelin breakdown and repair is continually occurring over the brain’s entire neural network,” said Bartzokis, who is also a member of UCLA’s Ahmanson-Lovelace Brain Mapping Centre.

“But in older age, we begin losing the repair battle. That means the average performance of the networks gradually declines with age at an accelerating rate,” he added.

In the study, each of the 72 participants had a magnetic resonance imaging (MRI) scan that measured the myelin integrity in the vulnerable wiring of their brain’s frontal lobes. The maximum finger-tapping speed over a 10-second period was measured just before MRI evaluation.

The results supported what had been suspected, that finger-tapping speed and myelin integrity measurements were correlated and “had lifespan trajectories that were virtually indistinguishable”, according to Bartzokis. And yes, they both peaked at 39 years of age and declined with an accelerating trajectory thereafter.

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