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Scientists Say Nerves Use Sound, Not Electricity
gazzarda writes "The CBC is reporting that a team of Danish scientists are claiming that nerve impulses are transmitted by sound and not electricity. 'The common view that nerves transmit impulses through electricity is wrong and that they really transmit sound, according to a team of Danish scientists. The Copenhagen University researchers argue that biology and medical textbooks that say nerves relay electrical impulses from the brain to the rest of the body are incorrect.'"
IAAANS (I am also a neuroscientist) and I'm with you on this. TFA sounds pretty crackpot to me. If they really had strong evidence for this it would be published in Nature, not Biophysical Journal.
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On further review, it seems that the CBC article is total crap, but that the original paper isn't that far off the deep end. I admit that I don't know enough to really follow or critique the research, but it doesn't seem to be the crackpot theory that TFA implies. Nowhere, for example, does that paper say that nerves don't use electricity. In fact, the paper refers to "solitons" as a piezo-electric effect. They are merely proposing a new mechanism on top of previous theories, not trying to completely throw out all neuroscience to date.
To recap: Completely bogus headline, based on a completely bogus bit of popular science reporting, which itself is based on a possibly intriguing (but tentative) bit of original research. Nothing to see here.
Here's the actual article. 099754v1.pdf
http://www.biophysj.org/cgi/rapidpdf/biophysj.106
They build upon Meyer & Overton's work & specificly say that Hodgkin-Huxley is not satisfactory with relation to anestethics.
My question is: Does the Meyer-Overton rule mean that elephant tranquilizers are 10,000 more times soluble than morphine?
[Fuck Beta]
o0t!
Every cell in your body is encapsulated by a cell membrane that is essentially two layers of lipids. It's not a real revelation that many drugs' effectiveness is enhanced by lipid-solubility.
"No, no, no. Don't tug on that. You never know what it might be attached to."
Looks like it actually made PNAS about a year and a half ago. http://www.pnas.org/cgi/reprint/102/28/9790
Either way, the summary and the linked article look to be way off base.
Current courses through your body, not volts.
// MD_Update(&m,buf,j);
The conduction of nerve impulses is understood at a detailed molecular level. There are numerous experiments that have observed everything from individual charges and ions traveling through channels and careful electrical modeling, to rationally designed anaesthetics that interact with specific molecules and targeted modifications of channels.
Now, it's always a good idea to keep an open mind. But these people have presented no even remotely interesting evidence that we need a change in paradigms. They are simply nuts.
I will say that their physics seems reasonable - one should understand that when we say "sound" there can be several meanings to that word. In the article, they are talking about piezo-electric pulses which I can visualise as a pressure wave that creates voltages between synapses (forgive me if I'm murdering the biology here ;-)). Imagine your usual piezo-crystal (a simple example is the one in a wristwatch) that vibrates (pressure waves) when a voltage is applied. Well, the reverse can also happen (this is used in some species of microphones). The way I visualize their model is that a piezo-electric soliton (if I remember my group theory, it's a sort of a quantized sound wave which persists without being destroyed by background noise because it has a topological quantum number asociated with it) travels between synapses leading to a voltage between them. Now, the pressure wave exists in the surrounding medium, which contains the ions in solution. So, at the most one can interpret these findings to mean that neural conduction is more like current in a superconducting wire than electroplating :D. This is the essence of their transport theory (as I understand it).
Another thing to note is that the article is not written as a maverick physicist would. It is written in a way that only a proper experimental physicist would - theory -> prediction -> experiment -> comparison. And the thing they are evaluating is actually the effect of anasthetics on neural transport. So, they are simply not claiming stuff as the news site falsely overhypes. I for one find this article fascinating even though biophysics is not my field.
I don't see how this translates to the sensationalist headline (although it's not the poster's fault, the linked site is a Canadian news site. The fact that it's Canadian is irrelevant :D, but the fact that it's a news site is rather telling. Also, they couldn't reach the authors for comments, which probably explains the awkward spin on the research.
IAAANS (I am also a neuroscientist) and I'm with you on this. TFA sounds pretty crackpot to me. If they really had strong evidence for this it would be published in Nature, not Biophysical Journal.
I'm afraid Nature is rather conservative in that respect and their editorial policy is at least partly based on maintaining or raising their impact factor (it is a highly profitable publication after all). The only way they can do that is by ensuring that only articles that are likely to be frequently cited in the future are published (that's the critical number that figures in the calculation of impact factor). As a result, the argument that any ground-breaking research would be automatically published in Nature is simply not true. Quite the contrary in fact. Now, before people mistake this for flamebait :P, I'm simply saying that Nature prefers the "wait-and-watch" routine, sorta like the Nobel committee, which is notorious for awarding A. Einstein with the prize for the photoelectric effect and not special or general relativity :P. I'm sure Nature will publish these guys a few years down the road after they have garnered enough of a reputation (IF they are correct that is!).
I was just trying to point out the decisions involved in publishing with Nature. If people want to publish something quickly that will spur interest and spawn more research in that particular area, they do NOT publish in Nature; rather they would publish in a more "everyday" journal like Biophys. A Nature publication (unless you research frogs; for some reason frogs are hot in NATURE =D) is sorta like a fine wine. You just can't afford to waste time on it everyday ;). Plus, its rather dishearten
IAAP (I am a physicist) and an electical current is the movement of electrical charge. Consequently your "electrochemical state changes that propagate along nerve axons" are in fact electrical currents in the strictest sense of the word. When we have moving charge we have a current end of discussion.
The fact the propagation speed is much lower than when the electrical charge is an electron and the medium is a metal is entirely irrelevant. Lots of mediums exist that propagate electical current at much slower speeds than metals. I would also point out that propagation speed of an electrical current bears no relation to the velocity of the charge carriers either.
Electrons don't race down copper wires. The electric field moves at a good fraction of the speed of light, but the electrons themselves move at something like one metre per hour.
First, the Biophysical Journal is fairly respectable, and a much more appropriate place to publish work in this area. Second, the actual journal article in the Biophysical Journal does NOT say what the Slashdot and CBC titles say, so judging them on this basis is inappropriate. The article is an extension of a previously published model which shows that nerve signal propagation can be described as 100m/s piezo-electric soliton pulses, and it shows that these are dependent upon the phase transition temperatures for membranes.
I dont know if you RFA but tbey didnt exactly provide any data.
If sound propagated down a nerve by sound, it'd end there. There's no mechanism to produce sound when a neurotransmitter from the first nerve mated with a receptor on the next.
Also, we listen to brain waves with an EEG or MEG, which measure minute electrical or magnetic impulses. We do not use a microphone and amplifier. Plus, we induce currents with electricity and magnetism, not loudspeakers, and produce predictable results.
Sound waves of sufficient intensity to propagate the full length of a nerve would be so strong in the main trunk that they'd disrupt the transport mechanism carrying neurotransmitters down from the cell body. They'd isloate the nerve from participating in the local neural network.
A new theory should explain everything just as well as the old plus more. This one falls apart at the basics and can't handle some of the nuances.
If sound propagation were the key, all that sodium and potassium gating to change the local membrane charge would be useless, and nature hates that kind of waste.
"I may be synthetic, but I'm not stupid." -- Bishop 341-B
I can't but agree.
I and my collegues did a research on the relationship between two distant methods of protein function regulation. We thought it was pretty nice, so we sent it to a bunch of very high-impact journals. Most of them sent it back even without giving it to referees. The only one that did refused us because we had a bad referee, and refused to even read our (long and detailed) response to his/her comments. So, less than year ago, we ultimately settled for a good but not top-most journal, where it was warmly accepted.
A couple of months ago my group leader talked at a conference in USA where he talked also about the research in that article. An editor of one of the journals we tried to publish that more than a year ago came to my boss and said "Really nice and hot work, why don't you publish it for us?" The answer: "Because you didn't want it a year ago, and now it's already done."
Why this sudden change? Because our proposed mechanism was not even a blip on the radar when we did it. In the meantime a recognized leader of the field published on Science a work that independently hinted in the same direction (even if in a very different and even less interesting way), and only because Mr.Guru created the buzzword now we are beginning to be taken seriously. Really sad.
-- Patent no.123456: A way to personalize
Sure you can get DC sound. It's called wind.
Nobody else has this sig.
Well, the one meter per hour figure refers to the drift velocity. The electrons aren't actually flowing like water in a stream, they are bouncing around like mad at speeds much faster than one meter per hour but they have a slight tendency to drift in the direction of higher voltage. Averaged out, this drift velocity is very small but the electrons themselves are moving much faster.
I think this is why so many people get confused by electricity. The FIELD moves almost the speed of light, but it makes electrons drift very slowly, even though the electrons THEMSELVES are moving rapidly. It's all very hard to visualize at first.
No. You're talking about observed speed in a medium, not about 'c' (the absolute speed of light). The observed speed in medium being less than c is a result of charge interaction between matter and the EM wave (or polaritons from the QM perspective). "Light" (photons in QM) travel at c. Period.
Slow down: The Hodgkins Huxley model of neural conduction is far too well supported by experiment, and by the observed behavior changes of nerve in response to ionic concentrations. You can't just throw that out due to a lack of thermal effects.
Moreover, "heat produced by electrical conduction" and the like have to come from somewhere. The amount of energy processed by a cell is limited mostly by glucose metabolism. (We could chat about protein metabolism as well, but let's not get distracted.) That glucose metabolism and related heat production for keeping the cell active in other ways is far higher than that one would expect from electrical conduction by any model I know: delicately measuring "resistive" losses (which do not quite mean the same thing in electrolytic conduction, let me tell you!) is like measure the paint on rocks in an avalanche. You don't bother to measure it by heat or weight, you measure it by more obvious factors like color (or electrical potentials, in this case, since HH style experiments demonstrate it quite well).
Fortunately, the actual original article is much better than the confusing and misleading analysis in the Slashdot lead-in and the linked article.