Lev also found vestibular! Email or dm him on twitter :)

Can he stimulate happiness like TMS can?

Doing this via ultrasound might lower the barrier to treatment.

This is the coolest part! Turns out, the powers you need are actually lower than what is used for imaging babies :) We measured our probe with a hydrophone on a computer-controlled scanner to get the pressure field, and made sure that it's below diagnostic levels (the generally accepted mechanical index limit is 1.9 and ours was 0.4 peak). We also made sure to avoid the eyes and keep thermals in check.

That's reassuring, but not entirely reassuring. Fetuses are a bit further from the emitter. You're focusing the pressure waves, but what about peripheral pressure waves disrupting the brain?

<3 email me or dm us on twitter! links on the post.

A scary concept... I think the hardest part would be coupling the ultrasound through the air. But there are probably solutions..

Great idea for a control! Will have to try it if we set this up again..

doooooo ittttt :)

Ha, nope. We needed something to stabilize the probe and the plastic knife from lunch was within reach :)

Totally! We think this is because the brain is hard-wired evolutionarily to interpret smells by danger level first. So maybe there's just more "bad smell" receptors, or maybe the brain treats unknown smells as "uh oh, danger". Lots of cool stuff to test!

Haha, luckily not! It's a very speculative link, so we didn't want to talk about "AI" too much in the main post. But we originally got interested in this concept because we are interested in other forms of input to the brain (other than the classic reading, listening, watching, etc). The nose is interesting because it seems to have many independent basis vectors and very sharp discrimination ability, so it might be a sensor into which you can pack many inputs. LLMs are just a proof-by-example that ~1k input dimensions is enough to really encode semantic meaning.

I'd personally be very sceptical that the human brain could derive much meaning from smell beyond "smells bad don't eat" or "reminds me of something", but I guess I would have said the same about creating smells via ultrasound so what do I know.

Do you have a testable hypothesis about this or are you flailing in the dark?

Totally agree with both points! I would love to see what happens with more fine-grained control of the ultrasound.

Woah, that would be wild! It seems like most neonatal ultrasound reaches peak internal pressures of few-hundred kPa to 2 MPa. We ranged from 150-250 kPa. So, a little lower than the lower end of prenatal diagnostic imaging.

So, the pressures are high enough to be stimulating them! But most diagnostic imaging happens at 1-20 MHz, while most neurostimulation seems to occur at few-hundred kHz (we were at 300 kHz, on the mid-high end). So I don't think it's likely that babies are being sent smells?