Adults well into their 70s can generate hundreds of new neurons a day — just as much as young people — according to a study that disputes previous findings that brain activity slows down as people age.
Researchers at Columbia University in New York found that many older people remain more cognitively and emotionally intact than previously thought. Their findings on the growth and development of the nervous tissue, called neurogenesis, were published Thursday in the journal Cell.
“We found that older people have similar ability to make thousands of hippocampal new neurons from progenitor cells as younger people do,” Maura Boldrini, an associate professor of neurobiology at Columbia University, said in a press release. “We also found equivalent volumes of the hippocampus [a brain structure used for emotion and cognition] across ages. Nevertheless, older individuals had less vascularization and maybe less ability of new neurons to make connections.”
Examining the brains of 28 people who had died suddenly, researchers were able to see formed neurons and blood vessels’ within the entire human hippocampus soon after death for the first time. The hippocampus deals with emotional control and resiliency, as well as memory.
The 28 brains, from previously healthy people between the ages of 14 and 79, were chosen because they did not have cognitive impairment or depression and had not been taking antidepressants.
The researchers report that even the the oldest brains had produced new brain cells. “We found similar numbers of intermediate neural progenitors and thousands of immature neurons,” they wrote in the study.
But they also noticed older individuals form fewer new blood vessels inside the brain and have a smaller pool of progenitor cells. These descendants of stem cells are more constrained in their capacity to differentiate and renew on their own.
“It is possible that ongoing hippocampal neurogenesis sustains human-specific cognitive function throughout life and that declines may be linked to compromised cognitive-emotional resilience,” Maura said.
Previously, researchers found rodents’ and primates’ ability to generate new hippocampal cells declines with age. Until now, it was thought the same is true of humans.
One month ago, researchers at the University of California San Francisco reported in Nature that they couldn’t find neurogenesis after adolescence in humans after studying 59 human subjects who ranged in age from a 14-week-old fetus to a 77-year-old man.
The researchers in Arturo Alvarez-Buylla’s lab have doubts about the conclusions of the Columbia researchers.
“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 told the Los Angeles Times.
The UCSF researchers said they looked not just at protein markers associated with different types of cells, but also analyzed cell shape and structure with light and electron microscopes.
The brain samples by the two groups were obtained different ways. UCSF researchers received brain samples from hospitals in the United States, China and Spain that were not quickly frozen and were preserved with chemicals.
The Columbia researchers’ brains, however, were donated by families of the deceased at the time of death, and immediately frozen and stored at minus-112 degrees Fahrenheit
Boldrini told the Los Angeles Times that his team looked at the entire hippocampus, and the UCSF team was looking at thin slices of the tissue from a small fraction of the brain.
By Allen Cone