Dr. Maura Boldrini from New York's Columbia University, the study's primary author said that "the exciting part is that the neurons are there throughout a lifetime,” and that "it seems that indeed humans are different from mice – where [neuron production] goes down with age really fast – and this could mean that we need these neurons for our complex learning abilities and cognitive-behavioral responses to emotions."
Boldrini and her colleagues studied the hippocampus of 28 men and women aged from 17 to 79, all of whom were healthy prior to their death. Using certain techniques, they studied the degree of blood vessel formation, its volume, and the number of cells involved at each stage of maturity, in a region called the dentate gyrus, which is where neurons are formed.
“According to mice studies there are these pluripotent stem cells that are a pool of cells that don’t normally do anything, they are quiescent, and then they can undergo division,” said Boldrini. She also added that "those daughter cells are the ones that exponentially divide and make many more cells and differentiate towards becoming a neuron.”
While the team noticed that many of the original cells ended up dying off, they also found that there were plenty of newer neurons forming at the time of death, regardless of the person's age.
However, the researchers noted that these neurons weren't completely identical to the original ones. “Even though we make these new neurons, they might be less plastic, or maybe making fewer connections or migrating less,” said Boldrini.
The researchers noted that this decrease in brain plasticity might explain why typically healthy persons may end up becoming more emotionally vulnerable as they age. However, they also note that the new cells being formed may help protect the brain against emotional or cognitive decline.
According to Boldrini, it's now important to find out what occurs in the brains of those with emotional issues of who suffer from Alzheimer's. This is because if any differences in the formation of cells are observed, it could end up offering researchers new targets for treatment.
Dr. Niels Haan from Cardiff University was very enthusiastic about the findings, and said that "we know from work in animal models that adult-born neurons are required for various learning and memory processes, and there is some evidence suggesting neurogenesis is disrupted in human psychiatric conditions,” and he believes that "this is a promising area for potential treatments.”