March 29, 2016

"We grow, mostly, by dying."

A startling sentence, found in "Runs in the Family/New findings about schizophrenia rekindle old questions about genes and identity," by Siddhartha Mukherjee (in The New Yorker). Context:

Throughout the brain—particularly in the parts involved in cognition, memory, and learning—synapse pruning continues into our first three decades, which suggests that it may be responsible, in part, for the starburst of adaptive learning that characterizes the first decades of human life. We are hardwired not to be hardwired, and this anatomical plasticity may be the key to the plasticity of our minds.

In the winter of 2004, having joined the laboratory of Ben Barres, a neuroscientist at Stanford, [Beth] Stevens began to study the pruning of synapses in the visual system. “When I began my work in Ben’s lab, little was known about how specific synapses are eliminated,” she told me. “The pruning phenomenon was thought to be quite general.” There was evidence of synapse pruning in the cortex of the brain during learning, cognition, and the formation of memories. But Stevens and Barres focussed their attention on visual neurons, because they were the easiest to study: the eye would be the eye to the brain.

In 2007, they announced a startling discovery. Stevens was trying to identify the proteins that recognized and eliminated neuronal synapses during visual development. “The strangest finding was that a protein that usually tags and removes pieces of dead cells, bacterial remnants, or cellular debris was also being reworked to tag and remove the synapses,” she said. Mice designed to lack tagging proteins—called complement proteins—had problems both in clearing cellular debris and in tagging and pruning their synapses.

The Stevens and Barres study, published in the journal Cell in 2007, documented one of the most arresting instances of repurposing in biology: a protein designed to ticket germs and junk for destruction had been co-opted by the nervous system to ticket synapses for destruction. “It reinforces an old intuition,” my psychiatrist friend Hans, in Boston, told me. “The secret of learning is the systematic elimination of excess. We grow, mostly, by dying.”

11 comments:

Eric the Fruit Bat said...

Sounds a bit like that thing from Cheers where Cliff explains why drinking makes you smarter.

Fernandinande said...

"gene" = “Abhed,” ... It means “indivisible” or “impenetrable,” but it is also used loosely to denote “identity.”

So Bengali doesn't have a word for "gene" and that's supposed to be philosophical. Or maybe just lame.

If one wishes to ponder "questions about genes and identity" ...

Genetic ancestry and brain morphology
"Population structure -- i.e., distribution of gene variants by ancestral group -- is reflected in brain morphology, as measured using MRI. Brain morphology measurements can be used to predict ancestry."

madAsHell said...

predict ancestry

Jumbo shrimp!!

Bob Boyd said...

"In the beginner's mind there are many possibilities, but in the expert's there are few" -Shunryu Suzuki

CStanley said...

In a different context, that's a pretty good Easter meditation.

n.n said...

Evolution is a chaotic process. Human life evolves from conception to death.

Bay Area Guy said...

.. a protein designed to ticket germs and junk for destruction..

Designed? Did someone say designed?:)

wildswan said...

"What if we needed to treat children long before their symptoms appeared; what if the treatment, in its attempts to normalize the psyche, interrupted the construction of individual selves?" from the article. A comment by a psychiatrist pointing out the risks of "treating" genetic risk for public health reasons before we really understand the mechanism. C4a when missing is associated with lupus, when present with learning, when "over-present", so to speak with schizophrenia. So treatment must be a right "dose".

But what is "right" in heterogenous populations? in a world mixed together? Will we say we know the right dose because we can trace an individual back to some continent through brain scans? overlooking all the changes and intermarriages since the world began to mix together? We don't even know why one gets the flu and dies and another gets it and lives. How can we say we know why one learns and another flips out?

Rhythm and Balls said...

Now this is the kind of science Aunty Althouse can get on board with!

Other science - not so much.

David said...

That was an outstanding article. Thanks for the link.

Valentine Smith said...

Sublime. Every cure a poison every poison a cure.