Do neuron electrical signals generate an electromagnetic field or wave?

[brajesh]

TL;DR

Do neuron electrical signals generate an electromagnetic field or wave?

I'm not sure where this belongs, I'm guessing biomedical, but I'm interested from a physics perspective.

Do neurons generate an electromagnetic field? In other words, all the neural activity in the brain, does it generate electromagnetic fields?
If so, what are the details of these fields?

I have questions like the following:

Can these EM fields exit the skull or is the skull too thick?
If they can't exit the skull, can they exit from the eyes or ears or nose, since there are holes in the skulls here?
What frequency and signal level are these fields?
What is the study of such a topic called?
Where can I find more details?
Perhaps people can communicate via emotions and no one has looked into this?

 

[atyy]

Neurons generate an electromagnetic field that can be measured at the skull, which is quite some distance from the neurons. The signal generated by a neuron is small, so it is generally thought that neurons must be synchronously active for their activity to sum to be large enough to be registered far away.

You can take a look at electroencephalography (EEG) and magnetoencephalography (MEG).
https://en.wikipedia.org/wiki/Electroencephalography
https://www.mayoclinic.org/tests-procedures/eeg/about/pac-20393875
https://en.wikipedia.org/wiki/Magnetoencephalography
http://ilabs.washington.edu/what-magnetoencephalography-meg

 

[brajesh]

Lots of materials for me to read - thank you @atyy

 

[BigDon]

As there are entire orders of creatures that hunt by being able to "see" the neuroactivity of their prey, I'd say most certainly. And not just at the skull. The organs for seeing neuroactivity from a distance are called "Ampules of Lorenzini". And most focus on detecting heartbeats, which the vast majority of vertebrates have little voluntary ability to "hold" like you can your breath.

This ability also let's creatures like sharks know the orientation of what they're observing, even at night or in murky waters. (The head end is always brighter than the tail end, and if human, then the flippers end.)

This is how great whites became famous for nearly always approaching from a diver's blind side.

 

[brajesh]

Wow fascinating @BigDon I didn't know this!
Do humans have such capability?

 

[jim mcnamara]

The lateral line in teleosts ("modern" bony fish) is thought to have re-evolved from Ampullae to do a similar job as the Ampullae in "less modern" cartilaginous fish. However. They sense pressure waves and low frequency sound waves instead of electric fields.

https://en.wikipedia.org/wiki/Lateral_line.

A marine biologist, late Eugenie Clark, used to say, "With your very first step into the water at the seashore, every higher vertebrate with 50 feet knows you are there with them." -- Ampullae and lateral lines at work.

 

[BigDon]

Mr. McNamara, you know what's even scarier that that?

Most crocodilians also have a lateral line system. So sensitive that both Nile and saltwater crocodiles don't even need to surface to know you're there. They can feel your footsteps along the bank!

 

[Frosted Flake]

Proton pump.

The nerve cells create an ambient, standing electric field by moving protons across the cell membrane. The signal is generated when the protons are allowed back into the axon, nullifying the electric field (grounding the bus?) very briefly, first at the triggered end of the nerve, then in a progressive fashion down the length of the nerve cell to the other end, where the signal triggers an effect. In this way the 'trigger' signal is passed from one place to another. The proton pumps automatically reset conditions inside the nerve cells, in less than a millisecond.

Or, so is my understanding.

 

[brajesh]

thank you for this explanation @Frosted Flake

 

[Fra]

Can these EM fields exit the skull or is the skull too thick?
What frequency and signal level are these fields?
What is the study of such a topic called?
...
Perhaps people can communicate via emotions and no one has looked into this?

What is routinley measured in EEG are the scalp potentials. This is the collective projection of all the impulses inside the brain. Often one wants to infer the 3D location from the scalp potentials. It's the inverse problem, and its not generally possible to do, but requires assumptions.

Looking at the instrumentation used, EEG voltages are typically measured in the 0.2 - 200 uV range and mostly in the 0.01-100 Hz domain. Different dominant frequency ranges are associated to different brain states. Transients processes or brainsteam reflexes involve higher frequences, but < 10 kHz, but these are so weak that they are buried in the noise and you need large ensemble averages to resolve the response from other noise.

Fields from a muscle, or heart us HUGE compared to even the collective neuro-potentials of the scalp. A human ECG is usually the order of 2 mV (0.05-150Hz) measured on the chest and is very robust to measure in comparasion to EEG, which picks up noise from all electrical stuff in the room and via cabling.

So to imagine the electroreceptors detecting detect brain waves in air is still something quite different than to detect large muscle activity in water.

/Fredrik