Not long ago, brain scientists believed that old brains didn’t make many new connections. They thought that our brains slow down as we age because we don’t make enough new neurons to replace those that naturally die.
In recent years, though, the results of some studies have challenged that theory, suggesting that even older brains continue to make many new neurons. Not all studies have found this, though, so it’s been a controversial topic. Now, even more sophisticated research has settled the question—at least for a key part of the brain responsible for learning and memory.
And the answer is…yes, healthy older brains make as many new neurons as younger brains do in a key part of the brain that is responsible for learning and memory. But there’s a catch: Just making new neurons is not enough to keep our minds fit. The new research sheds a little light on that, too—and what you can do about it.
The Brain’s Learning and Memory Center
Researchers from Columbia University Medical School set out to determine whether new neurons continue to be generated in a specific region of the hippocampus, the part of the brain that is responsible for learning and memory. They examined brains from deceased patients that had been preserved quickly enough after death to not have undergone too many physical changes. The deceased patients ranged in age from 14 to 79. (To reduce any influence from disease, brain donors were confirmed to not have cognitive impairment or any neurologic or psychiatric illnesses and to have no history of using medications that would affect reasoning or other thinking.)
Using specialized techniques and equipment, the researchers were able to “count” how many new blood vessels were being formed at the times of these patients deaths…and the quantities of different types of cells in several different parts of the hippocampus, each with different functions.
Results: The total volume of the dentate gyrus, the part of the hippocampus responsible for cognitive processing and making and recalling memories, was the same in brains that were in their eighth decade as in their second. Also, young neurons and specialized glia cells, which are essential to the function of neurons, were just as plentiful in older brains as in young ones.
The remarkably preserved specimens and the rigorous control of this study may account for why it found clear evidence of new neuron growth when some other studies haven’t. But it’s also worth noting again that the researchers excluded people with cognitive impairment such as dementia or neuropsychiatric illnesses such as depression. So it’s not known whether everyone’s brain keeps making so many new neurons and thus new connections. But it is evidence that our brains have the ability to keep significantly regenerating neurons, not only using old neurons—well throughout life.
What Older Brains Often Lack
What was different about older brains in the study? One thing stood out: Older brains did not have as many new blood vessels compared with younger brains. To function optimally, neurons need the nourishment and oxygen that is carried to them through blood vessels.
A key takeaway: Your brain can keep refreshing itself with new neurons—but it’s up to you to make sure that it gets the cardiovascular nourishment it needs. That means doing everything you can to stay physically fit and reduce your risk of heart disease and diabetes. If you keep the blood flowing, your brain might continue to help you remember well and learn new things for many, many years.