3 ms·
Modulation is part of the measurement process in that case. https://en.wikipedia.org/wiki/Lock-in_amplifier https://en.wikipedia.org/wiki/Lock-in_amplifier
by _Microft 2y ago
Modulation is part of the measurement process in that case.
https://en.wikipedia.org/wiki/Lock-in_amplifier https://en.wikipedia.org/wiki/Lock-in_amplifier
- bbor 2y agoHmm, 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...
- raffihotter 2y agoThanks for your questions! I was one of the people who worked on the project. To answer your questions: > 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? Since the system is linear, you could use a single probe to focus at multiple spots. Each focus would be at a slightly different modulation frequency. > 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? This method would indeed let you track signals that change over time. Lock-in-amplifiers can output time-varying signals.
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- bbor 2y agoI still have lots of questions, but I think that's on me haha. Thanks so much for taking the time for this, and for pushing forward the human race in such a groundbreaking manner. Hope y'all are doing well in these dark times.
- haccount 2y agoA modern clinical ultrasound probe have something in the range of 128 to 512 elements only. But despite that you get a real-time video stream at a lot higher resolution than a 512 pixel postage stamp.