This just in from the journal Cell: Your hippocampus, a key region for memory in your brain, makes a few hundred new neurons every day.
Does this mean you can now drink Tequila shots with impunity because you can more than make up for the brain cells you damage? Nope, no reason to think so. But the findings in Cell could have implications for future research in areas from antidepressants to Alzheimer’s disease.
Mainly, the new study helps cement the long-controversial claim that new neurons keep a-borning in the human brain all through life. And it does so in a creative new way, using carbon-14 left in humans by above-ground nuclear tests in the mid-20th century to measure the ages of brain cells.
I asked Prof. Joshua Sanes, director of Harvard University’s Center for Brain Science, to explain what the study could mean — why it matters whether our hippocampi keep making new neurons or not. His reply, lightly edited:
The basic dogma of neurobiology has been that you’re born with all the neurons you’re ever going to get, and then everything goes downhill from there.
But there was heated debate about this, and eventually, it was found in experimental animals that you do actually get new neurons throughout life — but weirdly, only in a few places. Where would depend on the species, but for mammals like us, it’s your olfactory bulb — what the heck that is about, nobody has any idea — and the other place is the hippocampus.
The hippocampus has proven to be critical to memory, and I’m not sure whether you’d say memories are stored there, but they certainly seem to be made there. You probably know about the famous patient HM: When he lost his hippocampus, he lost his ability to make memories.
So the idea arose that maybe if you’re making new neurons in the hippocampus, that’s to help you make new memories. In mice, there’s some evidence that favors that idea. I think nobody thinks it’s going to be as simple as that — that every time you need a new memory, you make a new neuron — but there are lots of experiments where they prevent the making of new neurons and somehow degrade memory in mice. And it seems that a lot of the things that a mouse does can affect how many new neurons are made, or at least how many of the new neurons that are made wire up.
One of those things is exercise: if you exercise more, you make, or keep, more new neurons. If you suffer a lot of stress, you make fewer neurons. Depression has been implicated; nobody knows how but there’s some idea that antidepressants can help you make new neurons, and if you’re depressed, you make fewer neurons.
So people have been interested in these new neurons, but nobody knew whether they were made in the human hippocampus, and this new study tells you that they are. Continue reading