Surely this is easily solved with time-reversed acoustics. Just stab a transmitter into the brain with an ice pick to the point you want to measure, and pick up the signal at lots of locations around the skull. Now you have both a mapping from an input signal (the reverse of the signal you picked up) that you can send to precisely target that point, and you know it looks like after it comes out from that point (the original signal you picked up).
Now you can tell exactly what is going on and the person is thinking! Specifically it'll be either: (1) "oh my god, I have an ice pick in my brain" or (2) nothing, because they have an ice pick in their brain.
Nah, this only works if you’re willing to leave the ice pick there, because the ice pick will have a wildly different speed of sound than the bone or brain, and it will scatter the ultrasound strongly as a result.
“The thing that nobody tells you is that you can buy a real human skull online (shoutout to skullsunlimited.com). We did that, and then CT scanned it.”
“People often quote 22 dB/cm/MHz attenuation of ultrasound. Decibels are a logarithmic scale, so with 1.4 cm of roundtrip skull distance, and typical fUSI frequencies of 10 MHz, this would be 14 orders of magnitude of attenuation! In physics, there's a word for 14 orders of magnitude of attenuation. It's called zero, i.e., you will measure nothing.
But where did the 22 dB/cm/MHz attenuation number come from? We were skeptical…”
They are planning to locally change the electrical conductivity of brain tissue by focused ultrasound, modulate that with at few hundred kHz and do a lock-in (EEG) measurement to deduce electrical activity at that spot on the scale of 1mm. Pretty wild if that actually works.
Fascinating — I thought ultrasound was already regularly in use for reading oxygenation levels, I had no idea it was new!! I’ve gotta try this. I don’t love the modulation side, but the measurement side is incredible. Invasive tech is unnecessary and terrifying IMHO
Hmm, I see, I think understand a bit better now -- thanks.
Is it fair to say that their claims about spatial resolution being >>> existing EEG options are jumping the gun? If I understand correctly, you need to be targeting individual 1mm^2 regions with individual acoustic lenses, which means 17,000 channels would required 17,000 separate, uniquely-tuned ultrasound emitters, yes? Even if that's possible without messing up the data (the MHz range is big, but is it that big?) it seems like a trivial impossibility to fit that in one headset -- even the standard 32-64 EEG channels alone seem like a long shot. But maybe I'm overly cynical, or one emitter could be used to usefully excite multiple regions at once?
Another oddity in that paper is that it reads like we're trying to find persistent signals in the brain, like a needle in a haystack, whereas my understanding was that the field is moving decisively towards tracking signal changes over time in a given region. Is my intuition correct that accounting for a moving target would add considerable complexity to this approach?
Either way, thanks for sharing the link. Definitely thought-provoking stuff...
Progress in making measurements through the skull useful might be how we finally get to precisely measure side-effects elsewhere: comparing healthy adult skulls to proper control groups. Always seemed odd to me how unspecific the thermal safety limits are, though the peak is expected depend on localized unknowns.
'Previous work showed that tofu is desirable as a phantom material, both because it is fast to get and because it has similar physical properties (density, speed of sound) as soft tissue.'
Haha wonderful.
Awesome! I know of efforts to leverage focused ultrasound to shorten sleep cycles and improve mental health. There’s so much more possible in neuroscience, great to see this work is gaining steam.
I think you are referring to slow-wave enhancement wrt "shorten sleep cycles", which probably isn't the right way to look at it.
We've been developing slow-wave enhancement for the past 4 years using auditory stimulation.
The problem with using focused ultrasound to accomplish this (I believe), is that the focal point creates heat, and I don't believe we want to be consistently creating hot spots of neurons in the brain.
Other methods (acoustic, visual, haptic) have proven efficacy by "tricking" the brain into increasing slow-wave delta power, and tMCS (magnetic) coaxes the neurons into a slow-wave pattern - though this is not realistic outside of a clinical setting atm.
Absolutely there is tons happening in neuroscience (lots here in Sydney, Aus), and focused ultrasound has it's place, but as a daily use, I'm not there with it yet.
For treatment of depression, for diagnosis, etc, absolutely. Though in depression treatment, SAINT protocol tCMS is very impressive.
I don’t know how much is public, the method I’ve seen “bounces” around and aims for a more global effect. Like a sonicare for the brain. No idea if it will work long-term as intended, but seems worth trying.
I recently had the idea to start a company that measures specifically properties of the pineal gland, I think people would pay for that. I have no domain expertise whatsoever. If anyone wants to investigate this deeper with me let me know
Money
Oh that sort of why
Because it's a spiritual thing, the yuppies who are also slightly hippies would want to see size and health and calcification %, more data sort of like a feedback loop like if you can do crunches and see more pronounced abs in the mirror, why wouldn't you want to meditate and drink and eat healthy and see if stuff changes in the physical state of the brain
Yeah I did a (mostly failed) PhD on ultrasonic imaging and found many things that worked in simulations but not in practice. The fancier your imaging algorithm gets the most ill posed it becomes and more sensitive to noise and errors.
Even if you add noise to your simulation , when you go to the real world it will have lots of sources of noise and errors that you didn't model. In this case I suspect aligning the CT scan with the ultrasound probe will be extremely difficult.
Also there's a reason ultrasonographers are so highly paid, and it's mostly used for pregnancies. In normal tissue it kind of sucks as an imaging method. (On an absolute scale; obviously it's amazing technology.)
Surely this is easily solved with time-reversed acoustics. Just stab a transmitter into the brain with an ice pick to the point you want to measure, and pick up the signal at lots of locations around the skull. Now you have both a mapping from an input signal (the reverse of the signal you picked up) that you can send to precisely target that point, and you know it looks like after it comes out from that point (the original signal you picked up).
Now you can tell exactly what is going on and the person is thinking! Specifically it'll be either: (1) "oh my god, I have an ice pick in my brain" or (2) nothing, because they have an ice pick in their brain.
Nah, this only works if you’re willing to leave the ice pick there, because the ice pick will have a wildly different speed of sound than the bone or brain, and it will scatter the ultrasound strongly as a result.
Yeah, that's fair. I guess you have to make the ice pick out of tofu.
“The thing that nobody tells you is that you can buy a real human skull online (shoutout to skullsunlimited.com). We did that, and then CT scanned it.”
This is an A+
When people "donate their body to science", they don't usually expect their parts getting sold to the public. But that's the reality of it.
“People often quote 22 dB/cm/MHz attenuation of ultrasound. Decibels are a logarithmic scale, so with 1.4 cm of roundtrip skull distance, and typical fUSI frequencies of 10 MHz, this would be 14 orders of magnitude of attenuation! In physics, there's a word for 14 orders of magnitude of attenuation. It's called zero, i.e., you will measure nothing.
But where did the 22 dB/cm/MHz attenuation number come from? We were skeptical…”
Skulls Unlimited really has their branding on point. I might just have to get one for the holidays.
Just a cool $1800 for a Halloween prop.
For that price, it's gonna somehow have to be included in _every_ holiday.
Skulloween, Skullmas, Skullsgiving...
I think there's a Tim Burton movie about that.
Also check out their other post: https://brainhack.vercel.app/ae
They are planning to locally change the electrical conductivity of brain tissue by focused ultrasound, modulate that with at few hundred kHz and do a lock-in (EEG) measurement to deduce electrical activity at that spot on the scale of 1mm. Pretty wild if that actually works.
Fascinating — I thought ultrasound was already regularly in use for reading oxygenation levels, I had no idea it was new!! I’ve gotta try this. I don’t love the modulation side, but the measurement side is incredible. Invasive tech is unnecessary and terrifying IMHO
Modulation is part of the measurement process in that case.
https://en.wikipedia.org/wiki/Lock-in_amplifier
Hmm, I see, I think understand a bit better now -- thanks.
Is it fair to say that their claims about spatial resolution being >>> existing EEG options are jumping the gun? If I understand correctly, you need to be targeting individual 1mm^2 regions with individual acoustic lenses, which means 17,000 channels would required 17,000 separate, uniquely-tuned ultrasound emitters, yes? Even if that's possible without messing up the data (the MHz range is big, but is it that big?) it seems like a trivial impossibility to fit that in one headset -- even the standard 32-64 EEG channels alone seem like a long shot. But maybe I'm overly cynical, or one emitter could be used to usefully excite multiple regions at once?
Another oddity in that paper is that it reads like we're trying to find persistent signals in the brain, like a needle in a haystack, whereas my understanding was that the field is moving decisively towards tracking signal changes over time in a given region. Is my intuition correct that accounting for a moving target would add considerable complexity to this approach?
Either way, thanks for sharing the link. Definitely thought-provoking stuff...
Progress in making measurements through the skull useful might be how we finally get to precisely measure side-effects elsewhere: comparing healthy adult skulls to proper control groups. Always seemed odd to me how unspecific the thermal safety limits are, though the peak is expected depend on localized unknowns.
'Previous work showed that tofu is desirable as a phantom material, both because it is fast to get and because it has similar physical properties (density, speed of sound) as soft tissue.' Haha wonderful.
Some say it tastes the same.
love the writing in this
"In physics, there's a word for 14 orders of magnitude of attenuation. It's called zero, i.e., you will measure nothing."
Lots of great sentences in here as noted in the other comments.
As a point of comparison, GNSS works down to about 16 orders of magnitude attenuation (dbw).
Awesome! I know of efforts to leverage focused ultrasound to shorten sleep cycles and improve mental health. There’s so much more possible in neuroscience, great to see this work is gaining steam.
I think you are referring to slow-wave enhancement wrt "shorten sleep cycles", which probably isn't the right way to look at it.
We've been developing slow-wave enhancement for the past 4 years using auditory stimulation.
The problem with using focused ultrasound to accomplish this (I believe), is that the focal point creates heat, and I don't believe we want to be consistently creating hot spots of neurons in the brain.
Other methods (acoustic, visual, haptic) have proven efficacy by "tricking" the brain into increasing slow-wave delta power, and tMCS (magnetic) coaxes the neurons into a slow-wave pattern - though this is not realistic outside of a clinical setting atm.
Absolutely there is tons happening in neuroscience (lots here in Sydney, Aus), and focused ultrasound has it's place, but as a daily use, I'm not there with it yet.
For treatment of depression, for diagnosis, etc, absolutely. Though in depression treatment, SAINT protocol tCMS is very impressive.
I don’t know how much is public, the method I’ve seen “bounces” around and aims for a more global effect. Like a sonicare for the brain. No idea if it will work long-term as intended, but seems worth trying.
I recently had the idea to start a company that measures specifically properties of the pineal gland, I think people would pay for that. I have no domain expertise whatsoever. If anyone wants to investigate this deeper with me let me know
Why?
Money Oh that sort of why Because it's a spiritual thing, the yuppies who are also slightly hippies would want to see size and health and calcification %, more data sort of like a feedback loop like if you can do crunches and see more pronounced abs in the mirror, why wouldn't you want to meditate and drink and eat healthy and see if stuff changes in the physical state of the brain
Yeah I did a (mostly failed) PhD on ultrasonic imaging and found many things that worked in simulations but not in practice. The fancier your imaging algorithm gets the most ill posed it becomes and more sensitive to noise and errors.
Even if you add noise to your simulation , when you go to the real world it will have lots of sources of noise and errors that you didn't model. In this case I suspect aligning the CT scan with the ultrasound probe will be extremely difficult.
Also there's a reason ultrasonographers are so highly paid, and it's mostly used for pregnancies. In normal tissue it kind of sucks as an imaging method. (On an absolute scale; obviously it's amazing technology.)
Eh maybe it will work though. You never know.