Brain breakdown begins in 40s.

• Position: Aging

Unraveling the mysteries of the aging brain is a major goal for science, especially given the exploding population of senior citizens and the obvious desire to preserve function for as long as possible. Now, researchers have uncovered a kind of genetic signature that may contribute to cognitive decline associated with aging.

One of the study's more surprising results was that these gene changes start in the 40s for some individuals. This raises intriguing questions about when and why the brain begins to age and the possibility of developing strategies to protect critical genes early in life in an attempt to preserve brain function and delay the onset of age-related conditions such as Alzheimer's disease.

To investigate age-associated molecular changes, Bruce A. Yankner, professor in the Department of Neurology and Division of Neuroscience at Children's Hospital Boston and Harvard Medical School, and colleagues examined patterns of gene expression in postmortem samples collected from 30 individuals ranging in age from 26 to 106 years. Using a screening technique called transcriptional profiling that evaluates thousands of genes at a time, the researchers identified two groups of genes with significantly altered expression levels in the brains of older individuals. A gene's expression level is an indicator of whether or not the gene is functioning properly.

"We found that genes that play a role in learning and memory were among those most significantly reduced in the aging human cortex," explains Yankner. "These include genes that are required for communication between neurons."

In addition to a reduction in genes important for cognitive function, there was an elevated expression of genes that are associated with stress and repair mechanisms and genes linked to inflammation and immune responses. This is evidence that pathological events may be occurring in the aging brain, possibly...