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Scientists shine a laser through a human head

spectrum.ieee.org

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Re: Scientists shine a laser through a human head

#21

Post by bbor »

This is a very interesting experiment, and props to the team involved! Exploring the frontiers of the possible is almost always worthwhile.

That said, in my humble (amateur!) opinion the framing from IEEE leaves a little to be desired, for one simple reason: they don't mention that most of what we're looking for is in the cortex (outer layer) of the brain, anyway!† And it kind of has to be, AFAIK... Namely;

fNIRS[1] is one of the four main brain imaging technologies (that I know of?): EEG, fMRI, fNIRS, and ultrasound. Like fMRI (& ultrasound?), fNIRS measures the oxygenation levels of different parts of the brain, which has been shown to be a close analogue for brain activity (more activity => more respiration, just like muscles). In this context, it's not enough to simply receive the signal you sent through -- you want to infer which emitter the signal came from so that you can infer the oxygenation levels of the regions it passed through/reflected-off-of.

All of that is a very amateur, high-level overview, but hopefully it clearly supports my underlying point/question: how could you possibly make this work with a cross-head emitter-detector setup?? It seems impossible to disentangle more than one emitter's signals, and I'm not sure how you'd map oxygenation levels without more than one. The diagram in the article seems to support this confusion, given how chaotic it is.

Then again, fNIRS and EEG both already rely on some serious statistical wizardy to turn 16-128 1D time series into a 3D model of activity, so perhaps I'm underestimating our tools! For example, the addition of frequency modulation to the fNIRS setup is an ongoing area of frontier research, which seems insanely complex to me.

P.S. In case any of the hackers here haven't heard yet: BCI (Brain-Computer interaction) is blowing up right now thanks to the unreasonable efficacy of LLMs for decoding brain activity[2][3][4], and it's a very hackable field! There's a healthy open-source community for both fNIRS[5] and EEG[6], and I can personally highly recommend the ~$1000 Unicorn EEG system[7] for hackers.

[1] https://en.wikipedia.org/wiki/Functional_near-infrared_spect...

[2] https://www.nature.com/articles/s42003-025-07731-7

[3] https://arxiv.org/abs/2309.14030v2

[4] https://arxiv.org/pdf/2401.03851

[5] https://openfnirs.org/2024/01/01/continuous-wave-spectroscop...

[6] https://openbci.com/

[7] https://www.gtec.at/product-configurator/unicorn-brain-inter...

†: As a human, you're not even a brain piloting a skeleton -- you're a 3mm wrap around the basic mammalian brain! https://en.wikipedia.org/wiki/Cerebral_cortex

Re: Scientists shine a laser through a human head

#23

Post by shadowgovt »

The next time someone asks me about quantum light effects, I'm going to try to remember this story.

"The quantum nature of light is why it's possible to shine a bright light through a human head without setting that head on fire... As long as it's the right color."

Re: Scientists shine a laser through a human head

#24

Post by astrobe_ »

ben_w wrote: post #13
hollerith wrote: post #11

>The group measured the times that millions of photons took to travel from a 1.2-watt laser emitting 800-nanometer wavelength light into one side of the head to a detector on the other side. Sunlight contains copious amounts of 800-nm light, so this is probably completely non-hazardous.

While it's almost certainly safe or it wouldn't have passed the ethics committee, what you say is an insufficiently detailed description of setup to determine if it's fine or not. 1.2 watts over your entire head is fine. 1.2 watts in a 800nm-diameter cylindrical path is "for some reason we decided to make the outer few millimetres of your skin explode, but we had to be in contact with your skin to manage that because…

What can one actually do with a 1 Watt laser? That's a good question to ask to an AI: "A 1-watt laser can be used for various applications, such as cutting materials, engraving, and even lighting cigarettes. However, it poses significant risks, including the potential to cause instant and permanent eye injuries, so safety precautions are essential".

So it looks like it packs some... Power. But I guess the frequency of the light makes all the difference, or maybe exposure duration?

Re: Scientists shine a laser through a human head

#25

Post by FirmwareBurner »

brenainn wrote: post #10
HelloUsername wrote: post #4

The title made me think of Anatoli Bugorski, a Soviet scientist who in 1978 survived a high-energy proton beam from a particle accelerator passing through his head. https://en.wikipedia.org/wiki/Anatoli_Bugorski

Me too! Amazing that he's still alive.

Yes but ...

"In 1996, Bugorski applied unsuccessfully for disability status to receive free epilepsy medication. Bugorski showed interest in making himself available for study to Western researchers but could not afford to leave Protvino."

This is just sad all around through and through.

Re: Scientists shine a laser through a human head

#26

Post by derbOac »

bbor wrote: post #21

This is a very interesting experiment, and props to the team involved! Exploring the frontiers of the possible is almost always worthwhile. That said, in my humble (amateur!) opinion the framing from IEEE leaves a little to be desired, for one simple reason: they don't mention that most of what we're looking for is in the cortex (outer layer) of the brain, anyway! † And it kind of has to be, AFAIK... Namely; fNIRS[1]…

> That said, in my humble (amateur!) opinion the framing from IEEE leaves a little to be desired, for one simple reason: they don't mention that most of what we're looking for is in the cortex (outer layer) of the brain, anyway!† And it kind of has to be, AFAIK...

I have friends who do research in this area pretty heavily and my impression is the same, that it's pretty limited to the outer layers of brain, and not super high in resolution.

There are advantages but they are more practical than anything else. Of course, practical can be critical but there a large percent of applications where it would have little utility. But hopefully things will improve.

Re: Scientists shine a laser through a human head

#28

Post by shadowgovt »

HelloUsername wrote: post #4

The title made me think of Anatoli Bugorski, a Soviet scientist who in 1978 survived a high-energy proton beam from a particle accelerator passing through his head. https://en.wikipedia.org/wiki/Anatoli_Bugorski

There's a lot of pieces of the physics of that story I don't quite understand. The main one is that (IIUC) one of the reasons the damage wasn't as bad as it could have been is that at the relativistic speeds the protons were travelling at, his head was extremely space-dilated, so they were basically blasting through tissue paper. But I would expect that tissue paper to have all the mass of a human head dilated into a thin disc, so the density would be far, far higher... Is density not a factor in proton-beam interactions with the material its interacting with (or is it more "it is, but total distance is a much larger factor")?

Re: Scientists shine a laser through a human head

#29

Post by cogman10 »

astrobe_ wrote: post #24
ben_w wrote: post #13

Earlier quoted context omitted.

While it's almost certainly safe or it wouldn't have passed the ethics committee, what you say is an insufficiently detailed description of setup to determine if it's fine or not. 1.2 watts over your entire head is fine. 1.2 watts in a 800nm-diameter cylindrical path is "for some reason we decided to make the outer few millimetres of your skin explode, but we had to be in contact with your skin to manage that because…

What can one actually do with a 1 Watt laser? That's a good question to ask to an AI: "A 1-watt laser can be used for various applications, such as cutting materials, engraving, and even lighting cigarettes. However, it poses significant risks, including the potential to cause instant and permanent eye injuries, so safety precautions are essential". So it looks like it packs some... Power. But I guess the frequency o…

Energy is what your looking for.

Static electricity discharges at around 400 to 600W. Yet it's for an extremely brief amount of time. Sub millisecond usually) so the actual energy transferred is minimal.

It takes around 1Wh to heat a liter of water 1 degree just to put things in perspective.

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