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Comment by oceliker | Hacker News Reader

> uses a bracelet to measure neuron activity in a subject’s arm to determine movement that person is thinking about, even if they aren’t physically moving

I don't understand how this could possibly work with an armband. They presumably are reading electrical signals from motor neurons, but why do they fire if there's no movement? Is it possible that they are detecting incredibly small movements that are involuntarily caused by thinking about moving your hand?

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This sounds straight like future-future-tech. My Fitbit can't even measure my heartbeat or steps with sufficient precision and they want to measure electric signals from neurons? Sounds (yet) impossible.

They had demos online. Unless they faked those

It's not even that new. A professor was using a much earlier version of this same tech to steer his boat in the 90's. It was very easy to read left and right signals to control a rudder as a prototype.

There have been commercialized versions of this tech already. The Myo was Kickstarted in 2015 and then acquired by CTRL-Labs. I have one and that generation of the tech was still tricky to use effectively.

https://www.kickstarter.com/projects/312488939/myowaretm-har...

Here's a pretty decent paper on the quite long history of Brain-Machine Interfaces: https://www.physiology.org/doi/full/10.1152/physrev.00027.20...

This is typical marketing speak. The device is measuring EMG. The motor neurons can fire without causing overt/obvious muscle movements, and these can be picked up still.

That's exactly what's doing. If you just think about moving your hand, pinching, whatever, then you are sending signals down that can be read.

if you were sending signals the muscle would move.

Not necessarily, you could have a gate at the very end that has to open up to let the signal through. There are inhibitory neurons throughout the nervous system, for example. It's also known that there is inhibitory circuitry that paralyses you while you are sleeping, so that you don't move while dreaming (see sleep paralysis for a common failure mode of this system). I have no ideas if motor signals do actually leave the brain when you are not moving though, it seems like an odd "design".

The inhibitory circuits exist in the brain and would prevent the motor cortex from sending out signals to the spinal cord. This device is reading motoneuron signals from the wrist when you are making movements. It's not mind-reading, the title is misleading.

As someone who has used these devices, you definitely do not need to actually move your hand

so , just imagining the movement, or "just about doing it" ?

They demonstrate (fake?) it in this video:

https://youtu.be/oD4efk8T2X4?t=83

(I linked to the specific time when it starts.)

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