UCLA neuroscientists using a new MRI analysis technique to examine myelin sheaths that insulate the brain's wiring report that as people age, neural connections that develop last degenerate first.
The computer-based analysis method is unique in its ability to examine specific brain structures in living people at millimeter resolution.
Published online by the Neurobiology of Aging earlier this year and scheduled to appear in the August 2004 print edition of the peer-reviewed journal, the study offers new insights into the role of myelin in brain aging and its contribution to the onset of Alzheimer's disease. In addition, the success of the MRI analysis technique opens new opportunities for studying the impact of lifestyle on brain aging and for developing medications that could slow aging or prevent Alzheimer's disease.
"The study increases our understanding of the role of myelin in brain development and degeneration, and demonstrates the usefulness of this MRI method for examining the single most powerful risk for Alzheimer's disease by far - age," said Dr. George Bartzokis, the study's lead investigator and visiting professor of neurology at the David Geffen School of Medicine at UCLA. He also is director of the UCLA Memory Disorders and Alzheimer's Disease Clinic and clinical core director of the UCLA Alzheimer's Disease Research Center.
Myelin is a sheet of lipid, or fat, with very high cholesterol content - the highest of any brain tissue. The high cholesterol content allows myelin to wrap tightly around axons, speeding messages through the brain by insulating these neural "wire" connections.
As the brain continues to develop in adulthood and as myelin is produced in greater and greater quantities, cholesterol levels in the brain grow and eventually promote the production of a toxic protein that together with other toxins attacks the brain. This toxic environment disrupts brain connections and eventually also leads to the brain/mind-destroying plaques and tangles visible years later in the cortex of Alzheimer's patients.
"The brain is not a computer, it is much more like the Internet," Bartzokis said. "The speed, quality and bandwidth of the connections determine its ability to process information, and all these depend in large part on the insulation that coats the brain's connecting wires.