Sound makes me feel

March 12, 2007 7:10 AM

Nerve pulses are sound pulses. The membrane of the nerve is composed of lipids, a material that is similar to olive oil. This material can change its state from liquid to solid with temperature. Molecules that dissolve in membranes can lower the freezing point of membranes. The scientists found that the nerve membrane has a freezing point, which is precisely suited to the propagation of these concentrated sound pulses. Their theoretical calculations lead them to the same conclusion: Nerve pulses are sound pulses. This comes from their work on the Thermodynamics of General Anesthesia (pdf). (via Stereophile?)
posted by caddis (43 comments total)

Their theory is that anesthesia works by lowering the freezing point of membranes in the nerves thereby reducing its ability to transmit. Transmit what? Something mechanical, they theorized that the transmission is of sound.
posted by caddis at 7:16 AM on March 12, 2007

If being able to transmit sound is enough to prove that they do transmit sound, what do they make of nerve cells being even more able to transmit electricity?

The physical laws of thermodynamics tell us that electrical impulses must produce heat as they travel along the nerve, but experiments find that no such heat is produced.

Whereas soundwaves don't produce heat?
posted by DU at 7:18 AM on March 12, 2007

This sounds insane. People have done tons of research on nerve cells, all of it based on nerves as carriers of electricity. Why, if nerves signals were based on sound, would sound of all frequencies have no effect on them?

Why, if sound were the medium of nerve signals would electricity have such a strong an effect on them? How would we be able to do everything from make frog legs jerk, to measure activity in the visual cortex with electrical probes.

This is time-cube stuff here. Also, I'm pretty sure the method by which anesthesia works is well known. This kind of research would be interesting like 150 years ago.
posted by delmoi at 7:23 AM on March 12, 2007

Also, how would this "nerves at their melting point" work in cold bloded animals, like fish? Their core tempratures can go through huge changes, and while it slows them down, it does not make them unable to feel pain.
posted by delmoi at 7:26 AM on March 12, 2007

Also, I'm pretty sure the method by which anesthesia works is well known. This kind of research would be interesting like 150 years ago.

Apparently, general anesthesia is not so well understood.
posted by caddis at 7:29 AM on March 12, 2007

Wow. When I learned of the Meyer-Overton rule (correlating anesthetic effectiveness and lipid solubility) a decade ago, it struck me as some isolated bit of knowledge badly in need connection to the rest of science. This seems to help build a bridge.

I'm pretty sure the method by which anesthesia works is well known.
I don't think so.
posted by exogenous at 7:40 AM on March 12, 2007

If nerves didn't use electricity, why would tasers work?
posted by Malor at 7:46 AM on March 12, 2007

IIRC when they discussed this on SLashdot they pretty much demolished it.
posted by Artw at 7:46 AM on March 12, 2007

IIRC when they discussed this on SLashdot they pretty much demolished it.

lol
posted by atrazine at 7:49 AM on March 12, 2007 [2 favorites]

I agree with delmoi; changes in the "freezing point" of the lipid bilayer membrane may well affect the propagation of electrical impulses as well as theoretical sound waves.

Remember, the electrical impulse carried through the neurons is not like the electricity carried through high-voltage wires; it is an electrical and a chemical phenomenon involving the opening and closing of voltage-gated sodium channels, which reverse the polarity of the axon (axons are long processes extending from the body of the neuron; they conduct nerve impulses); and this altered polarity is propagated down the length of the axon as more sodium channels open. Anything that alters membrane permeability of sodium and/or potassium, or the activity of the voltage-gated sodium channels (or the postassium "leak" channels) could alter the transmission of nerve impulses; the fact that these changes may also affect the transmission of hypothetical sound waves hinges upon the existence of these sound waves, which is pure speculation.
posted by Mister_A at 7:55 AM on March 12, 2007 [2 favorites]

This is ridiculous and doesn't even pass the laugh test. Yes, they laughed at Columbus. Yes, they laughed at the Wright Brothers. But they also laughed at Bozo the Clown.
posted by Justinian at 8:05 AM on March 12, 2007

Similiar in concept to Delay Line Memory.
posted by Mitheral at 8:10 AM on March 12, 2007

The problem is the reporting, not the research. The Slashdot people seemed to conclude the researchers weren't proposing that nerves work via sound waves, they were suggesting this as an additional effect on top of electrical conduction. Or something, I stopped paying attention fairly quickly.
posted by freedryk at 8:12 AM on March 12, 2007

This striking scientific discovery will open the floodgates for new and exciting discoveries in dopey techno songs sampling any available clips and referrences to being "anesthetized by sound"
posted by Uther Bentrazor at 8:13 AM on March 12, 2007 [1 favorite]

why can't i stop saying, "In this house we obey the laws of thermodynamics!" ?
posted by spish at 8:45 AM on March 12, 2007

Good news for audiophiles everywhere, who can now spend thousands of dollars on extra thick nerves with gold plated connectors.
posted by Joakim Ziegler at 8:46 AM on March 12, 2007 [3 favorites]

"extra think nerves with gold plated connectors" ~$17,000 (CAD) speaker cables must have nerves in 'em somewhere.
posted by spish at 8:52 AM on March 12, 2007

I'm currently doing my PhD in neuroscience - this is (yet again) another example of bad science reporting in the media. The researchers are investigated the relatively poorly understood mechanism by which anesthesia works (sorry delmoi, it hasn't been worked out today, let alone a 150 years ago - neuroscience is a young science and most of the majory discoveries have been in the last 75-50 years, not the past 150)... the main article is a relatively interesting article that suggests a new mechanism for anesthesia. Totally not crackpot science as the article works from theory to experiment to conclusions.

The bad bit of science reporting is that this work "over turns" well establish methods of neural communication - if true it merely adds another way for neurons to interact and does not "knock down" other well establish methods of neural communication. This work (an related work) is published in a reputable peer reviewed journal... sadly, it seems like people who did the summaries of this work neither read nor understood what was being said.
posted by christopher.taylor at 8:53 AM on March 12, 2007

Thanks, Christopher. I was looking for some good insight.
posted by Brainy at 9:14 AM on March 12, 2007

Action potential, we hardly knew ye!
posted by Turtles all the way down at 9:18 AM on March 12, 2007

That pdf is beautifully written and very clear; the first 5-6 pages discuss anesthesia more accessibly and convincingly than anything else I've read.
posted by jamjam at 9:20 AM on March 12, 2007 [1 favorite]

This is some seriously fringe "science." I can poke a hole in the linked text just by pointing out that ether, chloroform and xenon don't work as local anesthetics, which they should if this theory is correct.

Next, I can put needles into nerves and record the electrical transmissions with a voltmeter. And finally, I can stimulate the nerves with electricity, document the propagation of the resulting electric impulse, and show that it yields physiologically normal muscle contraction, just as the native electric impulse does.

Now, moving on to cell biology, we have the Goldman equation to let us understand the physiologic basis of these electric fields. Ultrastructuralists can show us nodes of Ranvier and demonstrate the presence of ion channels there.

The linked work doesn't take any of this prior work - some of it Nobel-wining - into account, and in fact contradicts it. I use the concepts of the electric field of the neuron every day in diagnosing and prescribing effective treatments to patients; I am not willing to discard it just because someone has a fancy looking website, filled with nutty ideas, that says "University of Copenhagen" at the top.
posted by ikkyu2 at 9:22 AM on March 12, 2007 [1 favorite]

Remember, the electrical impulse carried through the neurons is not like the electricity carried through high-voltage wires; it is an electrical and a chemical phenomenon involving the opening and closing of voltage-gated sodium channels...etc.

"Remember..."? You must have had much better high school science teachers than I did. Your comment, Mister_A, was an interesting mini-lesson for me.

(As a musician, I hope this theory has some validity--it will confirm my lifelong intuition that sound is far more important than than we currently think. Oh, and scientific insight and all that.)
posted by LooseFilter at 9:27 AM on March 12, 2007

I wonder what song my nerve cells are playing right now.

I bet it's Pachelbel's Canon.
posted by Kickstart70 at 9:35 AM on March 12, 2007

If nerves didn't use electricity, why would tasers work?

Faulty syllogism. Just because tasers use electricity doesn't mean that electricity is the means by which nerve signalling works. It only means that electricity has an effect on the nerves and muscles.

christopher.taylor makes a good point about alternate means of neural interaction. I'd like to see if this actually goes anywhere. Maybe it is completely bunk.
posted by RockCorpse at 9:41 AM on March 12, 2007

I bet it's Pachelbel's Canon.
*snort*
posted by Skorgu at 9:51 AM on March 12, 2007

Faulty syllogism. Just because tasers use electricity doesn't mean that electricity is the means by which nerve signalling works. It only means that electricity has an effect on the nerves and muscles.

It's a question, not a syllogism, and I don't see where it's faulty. Any new theory of nerve signal conduction will have to include that answer.

If nerves work as this fellow describes, he should be able to explain why tasers work. If he can't, then his theory is flawed. It needs to explain everything we already know about nerves, and a taser's effect is one of those things.
posted by Malor at 9:57 AM on March 12, 2007

This is an interesting post and discussion (despite the i-know-everything commments)
posted by serazin at 10:02 AM on March 12, 2007

I honestly can't count the number of times I've heard a surgeon say "hah, we knew anesthetists didn't know what they were doing"
Mr Wilder being a practitioner of the gaseous arts informed me many years ago of the fact that while we know an awful lot about how it works we fundamentally still do not know with certainty why it works.
Which is pretty important really. Loads and loads of theories, but a lovely mystery nonetheless.
This is badly reported but I love new theories. I'm hoping the sound waves shed some light on the subject. hah!
posted by Wilder at 10:08 AM on March 12, 2007

I'm willing to roll with shoddy scientific reporting, thanks to christopher.taylor's post. This is a particular shame, as I had a quite witty remark referencing Signore Galvani lined up.
posted by boo_radley at 10:08 AM on March 12, 2007

Thanks for posting this paper, caddis. It's really neat.

Nerve impulses do propagate a bit like sound waves in that both are known to be mediated by gradients in substances. The electrical impulse of a nerve is transmitted via changes in the concentration of electrically charged ions as they flood through voltage-gated channels in the cell membrane. It's not entirely unreasonable that there would be certain mathematical or thermodynamic similarities between nerve impulses and sound waves.

The freezing point of a membrane is a marker of its stiffness or fluidity. Cell membranes have all sorts of things floating around in them-- the ion channels, hormone receptors, and other proteins, various types of fat molecules, molecules with things attached to them that stick into or out of the cell, molecules connected to things, etc. Any of that can gum up or break up the system, so to speak, and change the freezing point. Since the interior of a cell membrane is made primarily of fat molecules, the small fat-soluble anaesthetic molecultes seem to be able to become embedded in the membrane and change its freezing point.

This doesn't negate the ion gradient dogma of nerve impulse transmission. But, as I understand it, this paper implies that something like a pressure gradient (i.e. a "sound wave") may also be involved.
posted by zennie at 10:20 AM on March 12, 2007

Metafilter: negating the ion gradient dogma of nerve impulse transmission

Oh, like you weren't thinking it...
posted by DesbaratsDays at 10:45 AM on March 12, 2007

exogenous, the correlation between lipid solubility and efficacy holds not just for anaesthetics but for a wide range of drugs. It has a lot more to do with how easy it is to get drugs into cells (excepting the few drugs which have an active uptake mechanism to get them in).
posted by oats at 10:48 AM on March 12, 2007

Mr Wilder being a practitioner of the gaseous arts informed me many years ago of the fact that while we know an awful lot about how it works we fundamentally still do not know with certainty why it works.

Good anesthesiologists can tell you more than this. They can tell you not only about a vast body of understanding possessed by the field; they can also be extremely specific about what is not known and what sorts of experiments or studies could be performed to learn the answers to these specific questions.

When people who have no grounding in the body of knowledge recite overheard proclamations of ignorance, you do well to consider the source and the context when evaluating such recitations for their worth. I say they are not worth a damned hill of beans.

Finally, bad anesthesiologists probably don't know how or why anything they do works. "Empiricist" has been an insult applied to unskilled practitioners of medicine for centuries. It is still valid to describe the worst, shoddy sort of medical practice.
posted by ikkyu2 at 11:29 AM on March 12, 2007

It's worth reading the conclusion of the actual paper; the claims made there aren't nearly as wildly speculative as those in the press release. Now, the PI might be a bit of an iconoclast, which is why the press release makes such strong claims, but it looks like the reviewers kept these claims out of the actual paper. In the intro to the paper, the authors even go out of their way to say "Moreover, it is to be emphasized that thermodynamics is not inimical to microscopic (e.g., ion-channel) descriptions of the same phenomena." There is a mention of soliton propagation in lipid membranes, but this is based on strong previous work by the researchers, and it not argued strongly as an alternative mechanism of signal propagation (though the suggestion is definitely there).

This paper does look like a piece of a strong argument that the properties of anesthesia can be understood in a thermodynamic framework. If anesthetics do function by altering the phase properties of bilayers, I think effects on lipid raft-related signaling are a more likely explanation than some bizarre new mechanism of signal propagation.
posted by mr_roboto at 1:47 PM on March 12, 2007

While not actually being knowledgeable enough to add to the conversation, can I just congratulate Mister_A for using the expression "reverse the polarity" in a serious sentence that doesn't involve treknobabble?
posted by Sparx at 1:53 PM on March 12, 2007

Why, if nerves signals were based on sound, would sound of all frequencies have no effect on them?

The hell you say. You really should come over and let me and some of my friends DJ and play our synths and computers for you.

Here, just sit over on this bassbin. There's a reason why we call it "the orgasmatron".

You might want to put these earplugs in. Also, any loose teeth? Heart conditions? Any history of epilepsy or mental illness in your family? This is an e-ticket ride. Please activate your listening devices and central nervous system and hold the fuck on.
posted by loquacious at 3:39 PM on March 12, 2007

This is ridiculous and doesn't even pass the laugh test. Yes, they laughed at Columbus. Yes, they laughed at the Wright Brothers. But they also laughed at Bozo the Clown.

And lacking either the familial ties of the Wrights, or the financial backing of Columbus, his groundbreaking research and thesis 'Applications of kinetic energies and Impacts of gelled Musaceae Musa' was wrongly discredited, and is still misunderstood to this day.
posted by SomeOneElse at 5:38 PM on March 12, 2007

Just to add to the flake factor: the yogic concept of sound, energy and nerves as expressed in the Sanskrit word "Shabd", which means sound. A NYC oncologist, Mitchell Gaynor, who uses sound/music, partly as pain relief, in his treatment of cancer.
posted by nickyskye at 7:08 PM on March 12, 2007

Having given a careful reading to the linked pdf, which is a peer-reviewed academic editorial, I'm struck that it has almost nothing to do with the headline link in this post. In particular, there's nothing in it about sound at all - just "physical properties," and a proposal of a simple model to explain the effects of general anesthesia with regard to lipid solubilities.

Looking back over my old med school notes, I see that med students in 1996 were being taught that the properties of inhalable anesthetics were likely due to their physical effects on cell membranes - xenon is mentioned in my old notes - so that's hardly revolutionary.

In conclusion, it seems like the linked peer-reviewed article is an attempt to propose a particular mathematical model for an already well-known phenomenon. The other link I don't know what to do with - it's so way out there that my leading hypothesis is that it was created as a joke.
posted by ikkyu2 at 9:01 PM on March 12, 2007

The funny thing is that the U of Copenhagen link quotes one of the paper authors directly as indicating that "The physical laws of thermodynamics tell us that electrical impulses must produce heat as they travel along the nerve, but experiments find that no such heat is produced." Personally, I doubt it is sound, although if it is, wow. More plausible seems that some physical change in the membranes affects the ionic transport system. The paper hints at a quasi-mechanical/electrical mechanism in using the term "piezo-electric." Perhaps a mechanical change helps pulse the electrical/chemical change and it just acts like a sound wave physically. Whatever the mechanism, and clearly they don't know for sure, these guys have found some interesting correlations and have some interesting theories about a poorly understood pathway in the body. Sometimes a fresh approach, here physics rather than chemistry, paints a picture in enough of a different light to find something new. Who knows whether these guys have gone that far? They have more work to do in any event.
posted by caddis at 10:19 PM on March 12, 2007

ikkyu2 writes "In conclusion, it seems like the linked peer-reviewed article is an attempt to propose a particular mathematical model for an already well-known phenomenon. The other link I don't know what to do with - it's so way out there that my leading hypothesis is that it was created as a joke."

The authors' soliton hypothesis is spelled out in a previous publication, in the very prestigious Proceedings of the National Academy of Sciences. I haven't read this carefully yet (it's actually rather intimidating), but it looks like an incredibly original, well-executed piece of work. This stuff is pretty closely related to my own specific field of research, and I certainly wouldn't dismiss it out of hand. It might be daring and iconoclastic, but it is legitimate scientific inquiry, not crackpottery, and certainly not a joke.

Seriously, now that I've looked at that PNAS paper, I'm pretty impressed.

The press release was irresponsible, though.
posted by mr_roboto at 10:46 PM on March 12, 2007 [1 favorite]

The other link I don't know what to do with - it's so way out there that my leading hypothesis is that it was created as a joke.

I nearly laughed at the revelation that a lipid is a special material that, "can change its state from liquid to solid with temperature." But having spent more than my fair share of time trying to explain science to people, I didn't think this article was that bad, mangled though the conclusions were. It looks, to me, very much like a press release that was written by a scientist and subsequently edited by a PR person; writing science for the public is a tricky thing. Science writing is much more of an art than a science.
posted by zennie at 9:37 AM on March 13, 2007