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A study of brains aged between 43 and 87 suggests we may continue to make new brain cells throughout our lives. The finding could mean that adult brains are more capable of recovering from damage than we thought.

Although many of our tissues and organs renew themselves throughout our lives, it is thought that neurogenesis – the growth of new neurons – rarely occurs in adults. Now María Llorens-Martín at the Severo Ochoa Molecular Biology Centre in Spain and her colleagues have studied brain tissue samples from 13 deceased adults, looking for signs of new brain cells.

New neurons are made in the hippocampus – a region of the brain key to learning and memory – and as they mature from young to old, they make certain proteins. To identify these new cells, the team used four types of antibodies to detect these proteins, and found that they were all drawn to thousands of neurons across the samples.

When the team examined the cells making these proteins, they found a variety of neuron shapes and sizes. Llorens-Martín says this indicates these neurons are in the process of maturing, and therefore suggests they were made later in life.

“There is neurogenesis in older brains, and it is important for forming new memories,” says Llorens-Martín. “Even people in their 90s have to store new memories every day, so I’m not surprised we found this.”

Arturo Alvarez-Buylla at the University of California, San Francisco, doesn’t agree. “The morphology they show is all mature cells. My hunch is that these have been there for a long time,” he says. Evidence for new neuron growth in adults is not consistent, he says, and to truly prove that these are forming in adult brains, we would need to have a method that detects when cells are born – a technique currently missing from the neurology toolbox.

“I think what they’ve seen is cells that are either maturing very slowly so still have a trace of the protein from when they were formed, or for some reason they are upregulating this protein to modify the cell later in life,” says Alvarez-Buylla.

The hippocampus is one of the brain regions most affected by ��������𾱳����’s disease. Llorens-Martín and her team also examined brain tissue from 45 people with ��������𾱳����’s who died between age 52 and 97. They saw that these brains had fewer cells making the proteins associated with maturing neurons. Those who had more severe Alzheimer’s when they died had fewer of these proteins than those who had milder symptoms.

“Immature neurons are crucial for certain types of learning,” says Llorens-Martín. It is unclear whether having fewer new neurons leads to Alzheimer’s symptoms, or if it is the other way round, she says.