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Tags cetaceans , James Nestor , physiology

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Old 8th May 2018, 05:30 AM   #1
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Diving Reflex (and freediving and sperm whales)

James Nestor is a journalist who wrote a book about freediving. He makes a number of interesting albeit somewhat dubious claims here regarding physiology and biology: https://www.youtube.com/watch?v=R_ck0Nzdo_U

Some of what he says is scientifically grounded...but other stuff seems exaggerated. (For example at one point throws off a statement about sperm whales eating 60-foot long squid...which is larger for Architeuthis than has been verified, but is a fairly minor nitpick). Thoughts, anyone? How much of a kook is this guy...if at all? There is extensive scientific literature regarding the diving reflex in humans and other mammals, for example. But I'm having a little trouble finding/verifying consensus.
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Old 8th May 2018, 06:15 AM   #2
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I can't watch YouTube on this slow service. Could you post the claims?
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Old 8th May 2018, 08:04 AM   #3
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Old 8th May 2018, 12:15 PM   #4
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Originally Posted by William Parcher View Post
I can't watch YouTube on this slow service. Could you post the claims?
Yeah, sorry. Some of the claims Nestor makes are:
Originally Posted by James Nestor paraphrase
Freediving:

* Infants lose swim reflex when they learn how to walk
* Human heart rate lowers 25% on immersion in water
* Past 35 feet human body becomes negatively buoyant
* Air in lungs shrinks by half every thirty-three feet diver goes down
* Heart rates of freedivers recorded as low as 14 bpm - one recorded as low as 7 bpm. While still conscious. For reference: The human heart averages 60-100 bpm while at rest.
* Modern freedivers diving to 800 feet (on single breath of air - w/o scuba gear; these are upper-tier trained athletes).
* World record breath hold (while freediving) - 12+ minutes

Marine Biology:
* Marine animals don't swim away from freedivers; but do swim away from divers with scuba gear
* Only way to study some marine animals - such as sperm whales - is by freediving
* Humans or some humans can echolocate (think this one has been verified)
* Sperm whale echolocation clicks can vibrate human body to death
Some of these claims have a very clear scientific basis. I'm just not sure whether they all do - and whether to the extent and in the context Nestor claims; the latter of which I'm sorry if I haven't communicated.

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Old 8th May 2018, 12:25 PM   #5
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Quote:
.....The human heart rate averages 60-100 bpm while at rest.
No. Anyone who is up around 100 bpm is seriously unwell. 60 to 70 is the generally accepted average. Decent endurance athletes can have a resting pulse in the 40s (30s occasionally).
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Old 8th May 2018, 12:37 PM   #6
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Originally Posted by MikeG View Post
No. Anyone who is up around 100 bpm is seriously unwell. 60 to 70 is the generally accepted average. Decent endurance athletes can have a resting pulse in the 40s (30s occasionally).
Maybe. 60-100 are the numbers they teach us in nursing school...
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Old 8th May 2018, 01:21 PM   #7
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Quote:
* Infants lose swim reflex when they learn how to walk
Never heard of this. I have no knowledge one way or the other, but I could easily see that both happen near the same point in time developmentally. I would however be surprised to learn that the process of learning to walk actually affects the swim reflex, rather than it just being coincidental.

Quote:
* Past 35 feet human body becomes negatively buoyant
There is such a point, but to name a single depth seems silly. It's heavily dependent on how much air is in your lungs. It's possible (for some people) to be negatively buoyant at the surface by reducing the air in the lungs. Some divers need weights to be neutrally buoyant at that depth.

Quote:
* Air in lungs shrinks by half every thirty-three feet diver goes down
Definitely a simplification. At that depth, pressure is approximately double that above the surface. But the body isn't a thin-walled balloon. Some limited pressure is borne by the body, so the volume won't decrease by exactly half.

The bigger problem is that each 33feet increases the pressure by 1 atmosphere. So the volume doesn't halve each time. It would be 1/2, then 1/3, then 1/4, etc.
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Old 8th May 2018, 02:01 PM   #8
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* Marine animals don't swim away from freedivers; but do swim away from divers with scuba gear
* Only way to study some marine animals - such as sperm whales - is by freediving

The noise of the regulator exhaust might be part of this.
Divers using Closed Loop Rebreathers don't have the problem.
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Old 8th May 2018, 04:38 PM   #9
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Originally Posted by MikeG View Post
No. Anyone who is up around 100 bpm is seriously unwell. 60 to 70 is the generally accepted average. Decent endurance athletes can have a resting pulse in the 40s (30s occasionally).
Originally Posted by Shadowdweller View Post
Maybe. 60-100 are the numbers they teach us in nursing school...
I take a few dozen pulses a day (to screen potential donors of blood plasma). Our acceptable range is 50-100, or 40-100 in some cases if we know they're athletic. Of course, nobody told me the reasoning for the upper limit because all I need to know is what the limit is to do my part, but it's possible that the limit is not exactly based on ideal health and might include other considerations like that 80-100 might be unhealthy but still not pose any greater risk in donating, or that the donors' pulses usually go down while waiting to donate and donating...

Just from talking to the ones that are over the line (to tell them they can't donate today) or even close to it (because they might go over it next time if nothing is done to bring it down), it seems that most of those who are around 90 or more turn out to be people who took caffeine or tobacco within about the last hour or so, or exercised practically immediately before coming in (including just rushing to get there)... but not all. There are a handful with pulses in the 80s and 90s for no apparent reason and with no sign of anything (else) wrong or out of the ordinary. Sometimes they're already aware of it and have asked their doctors and been told "you have a high pulse and that's just the way it is". It appears to be their normal state.
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Old 9th May 2018, 06:02 AM   #10
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Not going to address everything. Overall he seems to be stretching some facts to create a narrative.

Humans do have a dive response and my understanding is that it’s a notably strong one for a land based mammal. It’s not comparable to that possessed by aquatic animals.

Infants can’t swim, they just wave their limbs around and some people interpret this as swimming. Most instinctively hold their breath and IIRC there are some structures that aid them in doing so that are lost later on but if these exist it seems likely that they are related to living inside a womb.

Having a point where you are negatively buoyant seems inevitable as the air inside your lungs is compressed.

Some people can do a rudimentary from of echolocation, but it’s not like it requires some exotic organ humans don’t possess. Most mammals could do the same. I’m more intrigued by the number of mammals can detect magnetic fields (Dogs, cows deer) and wonder if we don’t have some capacity for that as well.
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Old 9th May 2018, 06:54 AM   #11
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I am negatively buoyant when I exhale and thus can do fun pool tricks, like doing pushups on the bottom of the pool.

I took a swim class in college and there was a guy who was a wide receiver on the football team and he could not float at all.
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Old 9th May 2018, 07:02 AM   #12
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Originally Posted by bobdroege7 View Post
.......... there was a guy who was a wide receiver on the football team and he could not float at all.
I'm pretty much the same.
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Old 9th May 2018, 01:10 PM   #13
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Originally Posted by bobdroege7 View Post
I took a swim class in college and there was a guy who was a wide receiver on the football team and he could not float at all.
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Old 10th May 2018, 06:31 AM   #14
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Originally Posted by lomiller View Post
..... Iím more intrigued by the number of mammals can detect magnetic fields (Dogs, cows deer) and wonder if we donít have some capacity for that as well.
Isn't there an iron compound involved? If humans have it, we would know from the usual autopsies, or at least some done specifically.

But the ability to find your way back, or to give/follow directions, varies immensely.
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Old 10th May 2018, 10:39 AM   #15
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Originally Posted by casebro View Post
Isn't there an iron compound involved? If humans have it, we would know from the usual autopsies, or at least some done specifically.

But the ability to find your way back, or to give/follow directions, varies immensely.
I donít think an autopsy would necessarily show anything. In spite of the large number humans have taken apart over the years the tendency for Cow and Deer to line themselves up with magnetic fields was only identified from Google Earth imagery in 2008 while the paper suggesting dogs align themselves with magnetic fields when they poop only came out in 2015.
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Old 10th May 2018, 11:38 AM   #16
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Originally Posted by lomiller View Post
Infants can’t swim, they just wave their limbs around and some people interpret this as swimming. Most instinctively hold their breath and IIRC there are some structures that aid them in doing so that are lost later on but if these exist it seems likely that they are related to living inside a womb.
Indeed. Nestor doesn't actually make the claim IIRC that infants can actually swim (i.e. move themselves), though he kind of implies that the reflex might be linked to some sort of aquatic past. I'm more apt to believe in some sort of survival mechanism...the breath-holding part of the swim reflex, for example, is fairly important. Question in my mind is...why does it disappear?

Originally Posted by lomiller View Post
Some people can do a rudimentary from of echolocation, but it’s not like it requires some exotic organ humans don’t possess. Most mammals could do the same. I’m more intrigued by the number of mammals can detect magnetic fields (Dogs, cows deer) and wonder if we don’t have some capacity for that as well.
I'm personally much more impressed by the echolocation - for example, the clip of the blind man apparently riding a bike. Given that our nerves, sensory neurons, and muscle cells all work by voltage-gated ion flow, it's not that much of a stretch to imagine that magnetic fields (of at least certain field strengths) might be discernible in some circumstances.

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Old 11th May 2018, 08:44 PM   #17
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Originally Posted by lomiller View Post
I donít think an autopsy would necessarily show anything. In spite of the large number humans have taken apart over the years the tendency for Cow and Deer to line themselves up with magnetic fields was only identified from Google Earth imagery in 2008 while the paper suggesting dogs align themselves with magnetic fields when they poop only came out in 2015.
I was thinking in comparison to homing pigeons.
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Old 15th May 2018, 10:10 PM   #18
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Originally Posted by Shadowdweller View Post

I'm personally much more impressed by the echolocation - for example, the clip of the blind man apparently riding a bike.
Our brains have more than enough general processing power for simple echolocation. The fact that this ability can be evolved and specialized to do what dolphins and bats do is remarkable but the simple version doesn't seem all that impressive to me.

Originally Posted by Shadowdweller View Post
Given that our nerves, sensory neurons, and muscle cells all work by voltage-gated ion flow, it's not that much of a stretch to imagine that magnetic fields (of at least certain field strengths) might be discernible in some circumstances.
Our nerves operate via electrochemical signals not electromagnetic. There are no large conductors involved in which a magnetic field could be induced. This doesn't rule out magnetic fields interacting with sensory neurons or nerves but the effect would be really small. Microscopic bits of magnetic material would seem to be a more likely source for this sensory ability. IOW Unlike echolocation that can leverage existing brain+hearing magnetic field detection would seem to require an actual specialize sensory cells.
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Old 16th May 2018, 01:27 AM   #19
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Originally Posted by lomiller View Post
Our nerves operate via electrochemical signals not electromagnetic. There are no large conductors involved in which a magnetic field could be induced. This doesn't rule out magnetic fields interacting with sensory neurons or nerves but the effect would be really small. Microscopic bits of magnetic material would seem to be a more likely source for this sensory ability. IOW Unlike echolocation that can leverage existing brain+hearing magnetic field detection would seem to require an actual specialize sensory cells.
Magnetic fields are produced whenever there is movement of charged particles. Neurons produce distinct and measurable magnetic fields when firing en masse. There are neuroimaging tests that revolve around this concept. Example: http://ilabs.washington.edu/what-mag...halography-meg. Furthermore, despite the frequent presence of magnets in a host of quack medical and pseudoscientific practices, there has been very extensive and real research into the effects and potential therapeutic uses of magnetic fields on human physiology. Token examples:
https://www.sciencedirect.com/scienc...88245704000033
http://journals.plos.org/plosone/art...l.pone.0013883

The effects, of course, are neither simple, consistent, nor well understood. Naturally, there is a world of difference (/continuum of potential sensory acuity) between being able to sense the presence or absence of magnetic fields in some circumstances versus being able to pinpoint location or navigate long migrations based on the earth's magnetic field, as some birds have demonstrated. Just as there is a difference between hearing an echo and being able to produce a three-dimensional mental representation of nearby objects including texture, velocity, and potentially substances based on echoes.

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Old 16th May 2018, 06:46 AM   #20
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Originally Posted by Shadowdweller View Post
Magnetic fields are produced whenever there is movement of charged particles. Neurons produce distinct and measurable magnetic fields when firing en masse. There are neuroimaging tests that revolve around this concept. Example: http://ilabs.washington.edu/what-mag...halography-meg. Furthermore, despite the frequent presence of magnets in a host of quack medical and pseudoscientific practices, there has been very extensive and real research into the effects and potential therapeutic uses of magnetic fields on human physiology. Token examples:
https://www.sciencedirect.com/scienc...88245704000033
http://journals.plos.org/plosone/art...l.pone.0013883

The effects, of course, are neither simple, consistent, nor well understood. Naturally, there is a world of difference (/continuum of potential sensory acuity) between being able to sense the presence or absence of magnetic fields in some circumstances versus being able to pinpoint location or navigate long migrations based on the earth's magnetic field, as some birds have demonstrated. Just as there is a difference between hearing an echo and being able to produce a three-dimensional mental representation of nearby objects including texture, velocity, and potentially substances based on echoes.
Again, though, you donít have charge moving down a conductor. That isnít how nerves and neurons work. Yes there is some physical movement of charged ions within a nerve cell and any movement of charge will create a tiny magnetic field but this is negligible. Your own link says it takes 100 000 simultaneous neurons firing to generate a measurable magnetic field.

This relationship is not symmetrical. Just because you can get a tiny magnetic field from an ion moving within a nerve cell when it fires, it does not mean that same nerve cell will fire in response to even a large magnetic field. This just not seem to be a viable mechanism for animals detecting magnetic fields, and research into exactly how animals detect magnetic fields is focusing on specific proteins that have the capability to function as a magnetic compass.
http://rsif.royalsocietypublishing.o...5/140/20180058
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Old 16th May 2018, 06:50 AM   #21
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Originally Posted by Shadowdweller View Post
Some of the claims Nestor makes are:
(...)
* Human heart rate lowers 25% on immersion in water
(...)

Doesn't seem to be the case:

Quote:
Heart disease participants had the same response as HC participants to the three experimental conditions (no significant between-group differences in all HRV variables). STW (immersion) caused in both groups to increase HRV when compared to supine and STL.
Acute effects of water immersion on heart rate variability in participants with heart disease.
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Old 16th May 2018, 07:25 AM   #22
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Originally Posted by dann View Post
Doesn't seem to be the case:
This appears to be looking at people standing in water. Dive reflex in humans appear to be triggered by holding your breath and immersing your face.
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Old 16th May 2018, 09:46 AM   #23
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But it only said "on immersion in water". At that point there was nothing about holding your breath etc.
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Old 16th May 2018, 10:44 AM   #24
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Originally Posted by lomiller View Post
This appears to be looking at people standing in water. Dive reflex in humans appear to be triggered by holding your breath and immersing your face.
Scuba divers find that their heart rate increases when they are under the surface. Lowering the rate is something you have to work at.
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Old 16th May 2018, 10:59 AM   #25
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So? Why is it essential for them to document every detail? Itís not a controversial subject and there are plenty of resources that more completely document the dive reflex
https://en.wikipedia.org/wiki/Diving_reflex

Originally Posted by Captain_Swoop View Post
Scuba divers find that their heart rate increases when they are under the surface. Lowering the rate is something you have to work at.
SCUBA divers donít hold their breath and mostly keep their face/nostrils dry.
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Old 16th May 2018, 01:19 PM   #26
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Originally Posted by lomiller View Post
Our brains have more than enough general processing power for simple echolocation. The fact that this ability can be evolved and specialized to do what dolphins and bats do is remarkable but the simple version doesn't seem all that impressive to me.



Our nerves operate via electrochemical signals not electromagnetic. There are no large conductors involved in which a magnetic field could be induced. This doesn't rule out magnetic fields interacting with sensory neurons or nerves but the effect would be really small. Microscopic bits of magnetic material would seem to be a more likely source for this sensory ability. IOW Unlike echolocation that can leverage existing brain+hearing magnetic field detection would seem to require an actual specialize sensory cells.
Gahead, read about magnetosensory and cryptochromes. Exactly those "actual specialize sensory cells"- in eyes.
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Old 16th May 2018, 01:32 PM   #27
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Originally Posted by Shadowdweller View Post
Indeed. Nestor doesn't actually make the claim IIRC that infants can actually swim (i.e. move themselves), though he kind of implies that the reflex might be linked to some sort of aquatic past. I'm more apt to believe in some sort of survival mechanism...the breath-holding part of the swim reflex, for example, is fairly important. Question in my mind is...why does it disappear?

I'm personally much more impressed by the echolocation - for example, the clip of the blind man apparently riding a bike. Given that our nerves, sensory neurons, and muscle cells all work by voltage-gated ion flow, it's not that much of a stretch to imagine that magnetic fields (of at least certain field strengths) might be discernible in some circumstances.
There was a touching BBC Radio4 programme about that guy

Batman and Ethan

Quote:
Ethan was born blind. He's now a 10 year-old boy who collects sounds on his 51 dictaphones, composes music, and performs on stage in concerts. Until now he's been home-schooled, but last year he was offered a place at St Mary's Music School in Scotland - one of the best in the country. The problem is he struggles to get around.

This is where Batman comes in. His real name is Daniel Kish and like Ethan he's blind. He's a master of echolocation. He makes clicking noises - like a bat - to build a picture of the world around him. Neuroscientists have done experiments on him and found that he's managed to activate the visual part of his brain. He's taught people all over the world to "see through sound" and he's so good at it that he goes hiking, cycling and rock-climbing.

"Batman" (Daniel) comes to Scotland to spend 10 days with Ethan, to teach him echolocation and help him prepare for his new school. The documentary follows Ethan's progress as he learns from Daniel Kish. Listeners are introduced to the principles of echolocation, they follow Ethan practicing at home, on the train and at his new school. They're brought into Ethan's world, through music composed specially by Ethan, and they're with him on his birthday, on long walks in the Scottish hills, right through to his experience at school.

We follow Ethan up to his final day of term to find out how he's done, and see how he copes with his biggest challenge yet: playing an accordion solo with the orchestra at the school concert.

Produced and presented by Helena Merriman.
It's really interesting listening to Daniel Kish discussing how to navigate the school with Ethan ( avoid turning towards the attractively large echoey hall space, for example).

Well worth a listen if you have a few minutes.
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link is 2015 data (2013 Data below):
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US 16.4% of GDP of which 48.2% is public expenditure - 7.9% of GDP is public spending
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Old 16th May 2018, 01:47 PM   #28
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Originally Posted by lomiller View Post
Again, though, you donít have charge moving down a conductor. That isnít how nerves and neurons work. Yes there is some physical movement of charged ions within a nerve cell and any movement of charge will create a tiny magnetic field but this is negligible. Your own link says it takes 100 000 simultaneous neurons firing to generate a measurable magnetic field.

This relationship is not symmetrical. Just because you can get a tiny magnetic field from an ion moving within a nerve cell when it fires, it does not mean that same nerve cell will fire in response to even a large magnetic field. This just not seem to be a viable mechanism for animals detecting magnetic fields, and research into exactly how animals detect magnetic fields is focusing on specific proteins that have the capability to function as a magnetic compass.
http://rsif.royalsocietypublishing.o...5/140/20180058

There is Transcranial Magnetic Stimulation
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OECD healthcare spending
Expenditure on healthcare
http://www.oecd.org/els/health-systems/health-data.htm
link is 2015 data (2013 Data below):
UK 8.5% of GDP of which 83.3% is public expenditure - 7.1% of GDP is public spending
US 16.4% of GDP of which 48.2% is public expenditure - 7.9% of GDP is public spending
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Old 16th May 2018, 02:15 PM   #29
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TMS is a rapidly changing magnetic field. Because it can induce electrical currents, the effects it has on neural tissues are very different than static fields.
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Old 16th May 2018, 02:18 PM   #30
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Originally Posted by BowlOfRed View Post
TMS is a rapidly changing magnetic field. Because it can induce electrical currents, the effects it has on neural tissues are very different than static fields.
True, and even then they have to be targeted - otherwise MRI scans would cause some interesting effects.
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OECD healthcare spending
Expenditure on healthcare
http://www.oecd.org/els/health-systems/health-data.htm
link is 2015 data (2013 Data below):
UK 8.5% of GDP of which 83.3% is public expenditure - 7.1% of GDP is public spending
US 16.4% of GDP of which 48.2% is public expenditure - 7.9% of GDP is public spending
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Old 16th May 2018, 02:43 PM   #31
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Originally Posted by lomiller View Post
Again, though, you don’t have charge moving down a conductor. That isn’t how nerves and neurons work.
Of course action potentials don't work like electron flow down a wire. They don't need to.

Originally Posted by lomiller View Post
Yes there is some physical movement of charged ions within a nerve cell and any movement of charge will create a tiny magnetic field but this is negligible. Your own link says it takes 100 000 simultaneous neurons firing to generate a measurable magnetic field.
Yeah that's about 2 cubic millimeters of CNS brain tissue, guy. Which is why MEG has diagnostic use. Of course, if we're discussing the ability to detect magnetic fields or be physiologically affected by them...then the magnetic field created by neurons themselves is irrelevant.

Originally Posted by lomiller View Post
This relationship is not symmetrical. Just because you can get a tiny magnetic field from an ion moving within a nerve cell when it fires, it does not mean that same nerve cell will fire in response to even a large magnetic field. This just not seem to be a viable mechanism for animals detecting magnetic fields, and research into exactly how animals detect magnetic fields is focusing on specific proteins that have the capability to function as a magnetic compass.
Magnetic fields do not need to (directly) trigger depolarization to be discernible or affect the body. They might merely change physiological systems in ways that are detectable by the organism. Consider, for example, possible effects such as changing diffusion / transport rates, depolarization thresholds, protein conformation...The proteins that comprise the ion channels which allow AP propagation (i.e. sodium/potassium flow), for instance, have charged domains that might conceivably have altered functionality in the presence of a magnetic field. I already posted link to a peer-reviewed microscale study showing EEG responses to magnetic fields. Here's another examining the effects on calcium channels (responsible for a host of functions in the human body).

Last edited by Shadowdweller; 16th May 2018 at 02:46 PM.
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Old 16th May 2018, 04:18 PM   #32
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Originally Posted by BowlOfRed View Post
TMS is a rapidly changing magnetic field. Because it can induce electrical currents, the effects it has on neural tissues are very different than static fields.
It's also using magnetic fields 50000 times stronger than the earths magnetic filed.
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Old 16th May 2018, 04:19 PM   #33
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Originally Posted by BowlOfRed View Post
TMS is a rapidly changing magnetic field. Because it can induce electrical currents, the effects it has on neural tissues are very different than static fields.
Are we confining ourselves to discussion of static fields? I don't recall that having been previously specified. There are plenty of things (e.g. AC power lines, electric appliances) in modern society that produce non-static fields; although for reasonable applications, the earth's field would be considered static.
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Old 17th May 2018, 01:24 AM   #34
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Originally Posted by dann View Post
But it only said "on immersion in water". At that point there was nothing about holding your breath etc.
This is possibly an artifact of my having improperly translated my notes from the originating vid to something intelligible to others The clip (or more specifically Nestor) itself was talking about the Diving Reflex in the context of a 300-foot freedive. One hopes the guy was holding his breath...since the alternative is drowning.

Last edited by Shadowdweller; 17th May 2018 at 01:38 AM.
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Old 17th May 2018, 02:52 AM   #35
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Originally Posted by jimbob View Post
There was a touching BBC Radio4 programme about that guy

Batman and Ethan



It's really interesting listening to Daniel Kish discussing how to navigate the school with Ethan ( avoid turning towards the attractively large echoey hall space, for example).

Well worth a listen if you have a few minutes.

David Clarke was blind from birth and was the England blind football team.

If I recall correctly he relied heavily on his ears, so much so that a scan revealed that large portions of his unused visual cortex had been co-opted by his hearing and was being used for 3d image processing. He said he didn't really need a noise, he could hear the surfaces around him being able to tell when, for instance, he passed a door in a corridor.

Amazing man.
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