Posted on 10/17/2008 1:13:32 PM PDT by decimon
It's more than just achy joints and arthritis, researchers say
During this year's baseball playoffs, Chicago White Sox outfielder Ken Griffey Jr., 38, threw a picture-perfect strike from center field to home plate to stop an opposing player from scoring. The White Sox ultimately won the game by a single run and clinched the division title.
Had Griffey been 40, it could be argued, he might not have made the throw in time. That's because in middle age, we begin to lose myelin — the fatty sheath of "insulation" that coats our nerve axons and allows for fast signaling bursts in our brains.
Reporting in the online version of the journal Neurobiology of Aging, Dr. George Bartzokis, professor of psychiatry at the UCLA Semel Institute for Neuroscience and Human Behavior at UCLA, and his colleagues compared how quickly a group of males ranging in age from 23 to 80 could perform a motor task and then correlated their performances to 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 aging may be primarily related to the process of myelin breakdown.
"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 Center and the UCLA Laboratory of Neuro Imaging. "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."
The researchers proposed that cognitive, sensory and motor processing speeds are all highly related to this decline. To test their hypothesis, they used one of the simplest and best understood tests of central nervous system processing speed: how fast an individual can tap their index finger.
It's well known that the speed of a movement increases with the frequency of neuronal action potential (AP) bursts in the brain. AP is an electrical discharge that travels over the axons connecting nerves, whether it's Ken Griffey Jr.'s brain ordering his arm to throw or the brain telling a finger to tap. Fast movements require high-frequency AP bursts that depend on excellent myelin integrity over the entire axon network involved in controlling that movement.
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 (the number of taps over a period of 10 seconds) was measured just before the MRI measure was obtained.
The results supported what the researcher had 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.
Bartzokis said these observations are consistent with the hypothesis that "maximum motor speeds depend upon high frequency AP bursts that, in turn, depend on the myelin integrity of the neural networks involved in the task."
"Beginning in middle age," he said, "the process of age-related myelin breakdown slowly erodes myelin's ability to support the very highest frequency AP bursts. That may well be why, besides achy joints and arthritis, even the fittest athletes retire and all older people move slower than they did when they were younger."
"The results are pretty striking," Bartzokis said. "The nearly identical trajectory across the lifespan for both measures of myelin integrity and fine motor speed supports the notion that myelin health underlies maximum AP burst frequency."
Significantly, the research suggests that the myelin breakdown process should also reduce all other brain functions for which performance speed is dependent on higher AP frequencies, including memory; it also supports the suggestion that myelin breakdown is a biological process of aging underlying the erosion of physical skills and cognitive decline, including the onset of such age-driven disorders as Alzheimer's disease.
There is, however, some good news, according to Bartzokis.
"Since in healthy individuals brain myelin breakdown begins to occur in middle age, there is a decades-long period during which therapeutic interventions could alter the course of brain aging and possibly delay age-driven degenerative brain disorders such as Alzheimer's," he said. "Non-invasive, serial evaluations of myelin integrity could be used to monitor the effects of new and current treatments that may slow the process of myelin breakdown as early as midlife."
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Other authors of the study included Po H. Lu, Kathleen Tingus, Mario F. Mendez, Aurore Richard, Douglas G. Peters, Bolanle Oluwadara, Katherine A. Barrall, J. Paul Finn, Pablo Villablanca, Paul M. Thompson, and Jim Mintz. The authors report no conflict of interest.
The study was supported by the National Institutes of Health, the RCS Alzheimer's Foundation, Sidell-Kagan Foundation; and the U.S. Department of Veterans Affairs.
The Semel Institute for Neuroscience and Human Behavior at UCLA is an interdisciplinary research and education institute devoted to the understanding of complex human behavior, including the genetic, biological, behavioral and sociocultural underpinnings of normal behavior, and the causes and consequences of neuropsychiatric disorders. In addition to conducting fundamental research, institute faculty members seek to develop effective treatments for neurological and psychiatric disorders, improve access to mental health services, and shape national health policy regarding neuropsychiatric disorders.
BZZZTTT! The FAA just raised the top age for airline pilots to 65. There is no age limit for commercial pilots/flight instructors/air taxis/ag fliers. This would not have happened had this article been true.
In fact I think the largest part of the brain by weight is the fatty acid components in the neural linings.
You need EPA and DHA your whole life.
Eat yur fish!
It’s brain food!
med/health bump
So what are the finger tapping rates and how do they relate to age?
"Cholesterol is good!"
What, is my name Craig? What so I know about tapping? ;-)
Very interesting. I have MS which causes destruction of myelin. That finger tapping test is part of a regular neuro exam. I can tap my finger on one hand, just fine, but on the other hand, the finger tapping is erratic, gets slower toward the end of the ten seconds, and not rhythmic at all...obviously because I have lesions affecting one side but not the other.
I don't see what one has to do with the other.
Also, independently, and perhaps a bit more relevant to your comment, I doubt that airline pilots are best measured by the speed of their reflexes. They can be a couple of a tenths of a second slow; what matters is that they are right, the chances of which experience in the cockpit can improve.
I don't mind flying behind an old pilot, so long as they are a good pilot.
Ping! For Later!
Wait a minute! What am I pinging and why? Is this about Obama HUSSEIN? Yikes, Thats Terrifying!
Just an editorial question because you posted the article.
BTW, are you? ;-)
Most of what we are is in our genes, and there is damn little that we can do about it.
Not me. I don't even have a stance.
Sorry to see you have MS and hope you find something to alleviate it.
Can you tell us what is that tapping test? A rapid tapping for some time period?
From the article:”To test their hypothesis, they used one of the simplest and best understood tests of central nervous system processing speed: how fast an individual can tap their index finger.”
How the test is administered is they have you take your index finger and tap it on a table for a specified period of time. First with one hand, then with the other. They observe if the tapping is equal on both sides, or if the tapping is impeded or erratic.
Some neuros just have you tap your thumb and forefinger together for a time.
Here’s a video of the test, the finger to thumb tap (scroll down to the Hand Rapid Alternating Movement video):
http://library.med.utah.edu/neurologicexam/html/coordination_normal.html
Thanks. I wasn’t sure if there was more to it.
thanks, bfl
Some years ago, I knew an older lady who was developing an “idiopathic neuropathy”, the loss of sensation in her toes, spreading to her feet, attributed to a breakdown of the myelin sheath around the nerves, and subsequent damage to them.
An herbalist recommended that she take, and continue to take, an extract of “milky oat seed”, in that it would generally arrest further decline. However, it would only help restore a small percentage of the damaged myelin sheath, and she would have to take it for the rest of her life, assuming the underlying neuropathy continued.
Interestingly, within a week her “pretty numb” feet developed a painful burning sensation, indicative of some nervous improvement, which settled down after a few days and left her with a little more feeling than she had, previously.
Unfortunately, out of laziness, I guess, she eventually discontinued taking the milky oat seed extract, and the neuropathy returned, leaving her with two numb feet and “drop foot” (loss of control of the foot). So now she must wear supporting braces and use a walker.
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