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The most recent memories and learned experiences that the brain registers appear to be the very connections that degenerate first. A new MRI analysis technique developed at UCLA and published in an upcoming Neurobiology of Aging Journal shows that the myelin sheaths that insulate the brain's wiring deteriorate in old age and to a greater extent in Alzheimer's patients. The study found specifically that the myelin in the brain's splenium and genu regions of the corpus callosum are particularly vulnerable. The splenium, which develops early in life, is important in vision amd the genu develops later for decision making, memory, impulse control and other higher functions.
The UCLA team found that the brain connections deteriorated three times as fast in the genu compared to the splenium. The study also notes that myelin deterioration is far greater throughout the brain of patients with Alzheimer's disease than in healthy older adults. The late myelinating regions are much more vulnerable and may be why the highest levels of reasoning and new memories are the first to go when one develops Alzheimer's disease, while movement and vision are unaffected until very late in the disease process.
The MRI technique is a safe, non-invasive technology that can assess the development and degeneration of the brain's myelin in specific regions. Now that we can measure how brain aging proceeds in vulnerable regions, we can measure what treatments will slow aging down and thus begin to look for ways to prevent Alzheimer's disease.
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