De-constructing Backyard Brain’s TED talk

** Images of dead animals ahead and reading this post sort of ruins the magic from the demo *** SPOILER ALERT

With over 2M hits on YouTube, this TED talk by Greg Gage from Backyard Brains was my one of my first insights into neuroscience. He demonstrates how to control someone’s hand with your brain.

As a maker and not knowing much about Neuroscience, me and my friends tried to replicate the same with some DIY kits but it failed. But why?

How to force muscle movement ?

Now with the help of some friends who actually study neuroscience,we were able to decipher the talk. The talk is subtle and doesn’t dwell into some technicalities which are essential to recreate the experiment.

Give a shock and muscles will twitch. This was known to scientists as early as 18th century through the experiments conducted by Galvani and Volta.

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                             Source: Academy of 21st century learning

Now you know that in order to make the legs of an organism twitch, you have to administer a shock to the right nerve.

EMG (Electromyograph)

An electromyograph detects the electric potential generated by muscle cells when these cells are activated. A typical processed signal from a EMG looks like so.

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                                    Source: Backyard brains

From looking at the data, the signal peaks when the hand is squeezed.
We set a threshold limit (T) beyond which it implies/ triggers that the hand has moved.

Now with a simple piece of code, you can administer a shock every time this threshold limit is passed and do whatever you want.

Here’s the legs of a frog being controlled by the hand:

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                                      Source: anasjaber

How to control someone else’s arm with your brain ?

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You need a device that takes in the EMG from one person and constantly looks out whether the threshold limit has passed.

If it did, a current stimulates the muscles of the other person and causes it to move. And that’s how you “control someone else’s arm with your brain.”

Have a good one!

* Electrical muscle stimulation for stroke recovery(video)

** Functional electrical stimulation

** We are by no means neuroscientists and have huge respect for the work done by Greg and his team at Backyard Brains. This post is not meant to undermine the work but to bring out the subtleties that belies it.