Scientists find signs of new brain cells in adults as old as 79

Do we continue to add new neurons to our brain circuitry throughout our lives? Or does our neuron count remain fixed once we reach adulthood?The scientific debate rages on.

In a report published last week in Cell Stem Cell, scientists from Columbia University present new evidence that our brains continue to make hundreds of new neurons a day, even after we reach our 70s, in a process known as neurogenesis.

To come to this conclusion, lead author Dr. Maura Boldrini, a research scientist at Columbia University's department of psychiatry, and her colleagues looked at the brains of 28 deceased people aged 14 to 79. Their goal was to see whether aging affects neuron production.

Previous research had shown that neurogenesis slows down in aging mice and non-human primates. Boldrini's group wanted to see whether a similar pattern occurred in humans.
In each brain sample the researchers looked for evidence of neurons in various stages of development, including stem cells, intermediate progenitor cells that would eventually become neurons, immature neurons that had not fully developed, and new neurons.

The team looked only at the hippocampus, in part because it is one of the few areas of the brain that previous research has shown can produce new neurons into adulthood. This region is involved in emotional control and resiliency, as well as memory, Boldrini said.
In all their samples the researchers found similar numbers of neural progenitor cells and immature neurons, regardless of age.
 
This led them to conclude that the human brain continues to make neurons even into old ageHowever, the researchers did uncover some differences in the brains of young people and older people.

Specifically, they found that development of new blood vessels in the brain decreases progressively as people get older. They also discovered that a protein associated with helping new neurons to make connections in the brain decreased with age.

We don't find fewer of the new neurons or fewer of the progenitors of new neurons, but we find that new neurons might make fewer connections," Boldrini said.This might explain why some older people suffer from memory loss or exhibit less emotional resiliency, she said.
These new findings were published one month after a team of researchers from the University of California, San Francisco reported in Nature that it was unable to find any evidence of neurogenesis after adolescence in humans at all.

In an email statement, that group, which works out of developmental neuroscientist Arturo Alvarez-Buylla's lab, said that while they found the new study's evidence of declining blood vessel growth in the adult hippocampus interesting, they are not convinced that Boldrini and her colleagues found conclusive evidence of adult neurogenesis.

"Based on the representative images they present, the cells they call new neurons in the adult hippocampus are very different in shape and appearance from what would be considered a young neuron in other species, or what we have observed in humans in young children," they wrote. 

They added that in their study, they looked not just at protein markers associated with different types of cells, as Boldrini and her team did, but also performed careful analysis of cell shape and structure using light and electron microscopes.
The debate continues (www.thespec.com)

By Deborah Netburn