In stark contrast to earlier findings, adults do not produce new nerve cells in a brain area important to memory and navigation, scientists conclude after scrutinizing 54 human brains spanning the age spectrum.
It would overturn the widely accepted and potentially powerful idea that in people, the memory-related hippocampus constantly churns out new neurons in adulthood.
Adult brains showed no signs of such turnover in that region, researchers reported November 13 at a meeting of the Society for Neuroscience in Washington, D.C. Previous studies in animals have hinted that boosting the birthrate of new neurons, a process called neurogenesis, in the hippocampus might enhance memory or learning abilities, combat depression and even stave off the mental decline that comes with dementia and old age.
The new study may temper those ambitions, at least for people. As expected, fetal and infant samples showed evidence of both dividing cells that give rise to new neurons and young neurons themselves in the hippocampus.
“We were unable to detect young neurons in adult human hippocampus,” study coauthor Shawn Sorrells of the University of California, San Francisco said in his presentation.
A landmark study, published in Nature Medicine in 1998, found newborn neurons in the hippocampi of people who, as part of their cancer treatment, had been dosed with an imaging molecule called BrdU that gets incorporated into the DNA of newly formed neurons.