Atomic Bombs Help Solve Brain Mystery

sciencehabit writes "The mushroom clouds produced by more than 500 nuclear bomb tests during the Cold War may have had a silver lining, after all. More than 50 years later, scientists have found a way to use radioactive carbon isotopes released into the atmosphere by nuclear testing to settle a long-standing debate in neuroscience: Does the adult human brain produce new neurons? After working to hone their technique for more than a decade, the researchers report that a small region of the human brain involved in memory makes new neurons throughout our lives — a continuous process of self-renewal that may aid learning."

Comments

Interesting...

[Black Parrot]

I just read this in a neuroscience textbook published last year.

Re:Interesting...

[AlecC]

According to TFA, the research which originally showed this could not be repeated since the chemical given to trace growth was found to be poisonous. Therefore it was based on a probably correct but unrepeatable experiment, something people in the hard sciences do not like. This new experiment has provided confirmation of the earlier result by a different method.

This isn't a mystery

[hedwards]

It's been known since at least the '60s that brain cells regenerate, the question was whether that applied to the grey matter or just the glial cells.

And AFAIK, it's been accepted for years that neurogenesis applies to grey cells. Arguing that it doesn't apply would require one to have an alternate explanation for why and how memory and learning occur after the brain supposedly doesn't create new neurons. Or how precisely all that development happens in the brain after birth.

Re:This isn't a mystery

[Black Parrot]

Arguing that it doesn't apply would require one to have an alternate explanation for why and how memory and learning occur after the brain supposedly doesn't create new neurons.

I was under the impression that the standard explanation was that learning and memory were based on connections, not generation of new cells.

Your impression is correct. You are born with (almost) all the neurons you will ever have. The density of synapses in your brain increases until you are ~18-20, then decreases somewhat and stabilizes. But the strength of the signal transmitted at any given synapse is subject to change at any time in your life, and is thought to be the mechanism for learning.

Re:This isn't a mystery

[Black Parrot]

BTW, the mention of learning in the article & summary isn't pure spin. The region they found that produces new cells is the hippocampus, which plays some kind of role in memory consolidation.

You'll have to ask an expert whether this is going to make us rethink anything about the mechanism for learning.

(Hope this isn't a dupe... I posted it earlier, but must have forgotten to click the Submit button.)

Re:Atomic bombs??

[Anonymous Coward]

I confess I RTFA (I'm sorry!), and you're wrong. It was the large increase in carbon-14 due to weapon testing that produced the measurable differences in the cadavers' brain tissue.

Re:Atomic bombs??

[Black Parrot]

It doesn't sound to me like nuclear weapon research had anything to do with this. If the link between nuclear research and this has anything to do with carbon-14 vs. carbon-12 then you can link this "brain discovery" to nearly any branch of research using carbon-14 dating...

It has nothing to do with carbon dating. As the A/C partially explains in another reply, the nuclear testing during the middle of last century increased the relative amount of C-14 in the environment, but it has been falling off since the test ban treaty went into effect in 1963.

Cells consist of lots of carbon, so *new* cells will be built out of whatever is available in the environment. Thus cells created before 1945 will have the "standard" ratio of C-12 and C-14, those created in the 1950s will have an increased proportion of C-14, and those created since 1963 will also have an increased proportion, though that increase has gotten smaller every year as the excess C-14 disappears from the environment.

So for cells created in the past ~100 years you can distinguish the pre-nuclear-testing ones from the later ones, and for cells created since 1963 you can give an approximate date based on the isotope ratio, since that ratio has been decreasing on a well-known curve.

People born before 1945 have the "standard" ratio of isotopes in most of the neurons in the brain, ergo those cells were created before 1945. People born more recently have an elevated ratio in most of the neurons in their brain, depending on what year they were born.

If new neurons were regularly created throughout life, people born before 1945 would also have an elevated ratio of the isotopes.

The news in TFA is that someone found a brain region with an elevated C-14 ratio in people born before nuclear testing started, and thus conclude that that region of the brain creates new cells later in life.