Fourth membrane is discovered in the brain | Hacker News Reader

Fourth membrane is discovered in the brain

newscientist.com

148 pointsatombender50 comments

A interesting factoid about this paper is that the first author Kjeld Møllgård, is a 80 year old former rector of University of Copenhagen. The Danish articles about that have been highlighting that, and that he now have to change what he is teaching after 50 years.

"factoid" is an incorrect fact. https://en.m.wikipedia.org/wiki/Factoid

From the first sentence in the article you're linking:

[...] or a true but brief or trivial item of news or information.

That link also mentions that it's used to refer to a brief or trivial true fact.

Factlet.

It's a factoid only until it hits ground truth. Then it becomes a factite.

Guys, it was a metajoke

He’s at my department at the Uni (well up until he retired), and the crazy thing is he’s been employed at the Uni for his whole adult life, since starting as a student helper at around 18.

I'm truly shocked that we're still adding knowledge to human anatomy. Physiology, sure, but anatomy? Haven't scientists looked at tens of thousands of brains?

From what I've read, neuroscience is in its infancy and there is so much which still needs to be understood. The brain is immensely complex.

I don’t know why you’ve been downvoted. The amount of knowledge we know of the brain than is significantly much lesser than what we don’t know. Heck, we’re still not sure if SSRIs work by increasing serotonin, reducing inflammation or increasing plasticity. Maybe all 3 are related.

Evolution has had millions of years to work on its craft. We’ve been studying it for an infinitesimal fraction of that time. There’s nothing surprising here.

The fly's brain has been deconstructed to finer resolution in the last ten years. The three dimensional model looks like a weather system. The threads in hardware/software could be made to thinly approximate that brain functioning for a minimalist flying dragonfly embodied micro controller.

Some years ago, there was a renewed discovery of a ligament [0] in the human knee, that is thought to be important for stability, especially after sport-related injuries.

Also, the mesentery [1] is only recently discovered as a separate organ, a sheet of connective tissue that supports and protects the intestine.

[0]: https://www.bbc.com/news/health-24826323

[1]: https://en.wikipedia.org/wiki/Mesentery

The glymphatic system has been discovered only 10 years ago it seems. And it’s still not that well understood.

A lot of this is due to advances in imaging, particularly two-photon microscopy, that enable acquiring images (and video to some extent) in live subjects, e.g. mice and rats, below the top surface of tissue. For neuroscience, you can either thin the skull or install a window, and image more than 100 microns into the brain, in live animals that are anesthetized or otherwise immobilized. Here's a nice article with an overview of two-photon for this purpose (direct PDF link): https://www.hifo.uzh.ch/research/helmchen/publication/helmch... that paper was published a while ago now, but the basics are still relevant. Two-photon played a big part in the identification of the "glymphatic system" initially as well. The Nedergaard lab does a lot of imaging, and they've built custom microscopes as well. (Source: I used to work in their department, and I'm doing my PhD work in the same building. edit: in Rochester, not at KU, though I visited there when they were first outfitting the lab space in Copenhagen.

I'm curious how we can have tens of thousands of people training for decades performing millions of neuro surgeries, not to mention however many autopsies and we didn't have a notion of this membrane or its function?

It's explained in the New Scientist article:

> It is extremely thin, with a width of just a few cells or, in places, even one cell. The SLYM hadn’t been noticed before, partly because the membrane disintegrates when the brain is removed from the skull in post-mortems, says Maiken Nedergaard at the University of Rochester Medical Center in New York, who helped discover the structure. It is also too thin to be seen in living people via brain-scanning machines.

I wonder what details we are not noticing about climate change, EV use, renewable energy, etc?

IMO, there is likely much more that we don't know that what we do know.

Why those things in particular?

Those are the things I believe we are rushing into without much of a plan. Inject sulfur into the atmosphere to cool down the earth? Mining all those heavy metals for EV batteries? And where is the electrical infrastructure for 100% EV and RE? (We can’t even keep the lights on when it is cold.). We should focus on adapting to climate change rather than trying to stop it. Attempting to stop it will be a losing cause. IMO, of course.

The detail of each part of our body make me think did evolution have enough time to produce all living things on earth? Any clue for this question?

It's really hard to understand just how much time there has been.

Life/nature is certainly amazing and incredibly complex. Earth has been around for about 1/3 of the age of the universe though. You could flip your question and ask why it's taken so long.

I mean how much time do you feel might reasonably be required for such systems to develop?

Think about orders of magnitude: last year, Russia’s invasion of Ukraine hadn’t yet begun. Ten years ago Obama was still president. Think of every single person that you know today - probably none of them were alive a hundred years ago. A thousand years ago the world was laughably low tech compared to today. Ten thousand years ago is already outside the domain of known/written history, iirc.

Now go back another ten thousand. And another. And another. And another. And another. And another. 200,000 years ago is the neighborhood where our distant ancestors started popping up in Africa - and they were hardly different from us, all those complicated structures were largely in place.

That’s two hundred thousand years. How long do you think life had to get to that point?

Mammals probably showed up two hundred million year ago.

Think about that for a second. The time it took for us to get from trees in Africa to typing on the internet? That happened ONE THOUSAND TIMES OVER between first mammals and first man.

How long before that? We’re already completely beyond the realm of human comprehension.

You think two hundred million is a long time? Try ~4 billion years, of life continuously living, breeding, mutating, and surviving. That’s the answer to your question. It’s been so long that creatures we have never heard of and will never know of have had time to live, flourish, and die off, utterly forgotten other than the genetic equivalent of a footnote if they’re lucky!

This is random genetic drift and selection / survival of the fittest played over and over and over for nearly as long as the earth itself has existed. We’ve had time.

Given how hard it is to observe, I guess it will be some time before we know how easily it gets damaged or how it gets repaired after trauma.

I wonder how many unexplained cerebral issues will eventually be found to be caused by malformations or damage of this membrane.

> SLYM is immunophenotypically distinct from the other meningeal layers in the human and mouse brain and represents a tight barrier for solutes of more than 3 kilodaltons, effectively subdividing the subarachnoid space into two different compartments. SLYM is the host for a large population of myeloid cells, the number of which increases in response to inflammation and aging, so this layer represents an innate immune niche ideally positioned to surveil the cerebrospinal fluid.

I learned a whole bunch of new words from you, thank you.

may you please unpack this sentence, as I dont know exactly it means:

>ideally positioned to surveil the cerebrospinal fluid.

The immune system needs to sample and test whatever is in the cerebrospinal fluid so that it knows when to activate.

More proof of where on the path of a mechanistic explanation of the brain, finding a whole new compartmentalization makes it seem like "not that far."

Biology always seems like the work of a mad hacker with no code reviews for a billion years.

> mad hacker

You might even say they were "insane in the membrane".

Thanks everyone, enjoy the veal!

INSANE IN THE BRAIN

Is this skepticism of the existence of a mechanistic explanation or just commentary on progress?

Commentary on its progress.

Not sure how a membrane that surrounds the brain is part of a mechanistic explanation of the brain (by which I assume you mean the mind). This seems to serve more of a CSF (cerebro-spinal fluid) filter function.

Maybe substitute "physicalistic" (as opposed to computational) for "mechanistic". I think there is something to the idea that physical layout could be tuned to use various waves (electromagnetic, fluid pressure, etc) for signaling. So it may not all be axons and dendrites, it might also work like a big capacitor / resonator, transmitting macro information through every worthwhile sidechannel. Who's to say all those side-channels are known to current science?

For all we know, we could have an interited quantum-coherent base pair linking us to all other living entities.

Or, if many-worlds is true, our entangled parallel selves!

I'm a firm believer in quantum immortality.

I assume you've seen this[1] story about quantum immortality, but other readers may not have.

[1] https://www.tor.com/2010/08/05/divided-by-infinity/

What does your first sentence mean?

If that was to me, it was subtweeting some of the optimism that we will be anble to fully simulate a human brain, including diffusion of mood affecting molecules, any day now. It is like the people that thought the genome had 100k genes and sequencing it would make it all understandable, only to find out there are just 30k genes and a lot we had no idea about. When your data gathering shows you had massive errors, you are not almost done understanding things.

Biology to me seems like the work of a billion years of iterations in an evolutionary neural network.

If the human body were a codebase, there's no way in hell it would work so well if it were the product of any other process.

Evolution by natural selection.

Here [1] is a New Scientist article about it. The tl;dr is:

> A new anatomical structure has been discovered that is part of the brain’s waste disposal system. The tissue is a thin membrane encasing the brain that keeps newly made cerebrospinal fluid – which circulates inside the brain – separate from “dirty” fluid containing cells’ waste products.

[1] https://www.newscientist.com/article/2353622-weve-just-disco...

Ok, we've changed to that from https://www.science.org/doi/10.1126/science.adc8810, which is hardwalled.

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