There are notably inconsistent results in whether targeting ultrasound to a given brain area increases or decreases neural activity in that area, even in some cases when the same area is targeted with the same sonication parameters! We clearly need to get a better sense of what ultrasound even does.
A somewhat related: a member of technical staff of Prophetic AI made public a technical overview in July:
It briefly discusses the history and competing theories of mechanisms of neuromodulation and mostly focuses on risks and safety, but it also has a diagram explaining “Activation vs. Inhibition across in-human tFUS studies” on page 15.
A somewhat related: a member of technical staff of Prophetic AI made public a technical overview in July:
Assessing the Risks and Safety of Neuromodulatory Transcranial Focused Ultrasound (tFUS) (via https://x.com/PropheticAI/status/1814307410011443395).
It briefly discusses the history and competing theories of mechanisms of neuromodulation and mostly focuses on risks and safety, but it also has a diagram explaining “Activation vs. Inhibition across in-human tFUS studies” on page 15.
This diagram is taken from the chapter “Transcranial Ultrasound Stimulation” of “Handbook of Neuroengineering” (2023) (beyond a paywall: https://link.springer.com/referencework/10.1007/978-981-16-5540-1?page=4 and https://link.springer.com/referenceworkentry/10.1007/978-981-16-5540-1_56).
I don’t know how firm this understanding is, whether this is just a “best guess”.