Multi-electrode arrays — reading and writing living neurons

22:55cluster as like the corollary in an artificial system? >> Yeah. Yeah. It's like the number of um it's the number of transistors one can think of maybe you know it's like I mean no it's not it's not quite because you know it's not one transistor to one artificial neuron but in your artificial neural network you have you know billions and billions of neurons with trillions of weights in between them here you've got 800,000 neurons it's still small but it's incredible what they're able to do with it >> understood >> you know but that's the idea you know okay so that's our neuron piece now let's get into How are we going to sense them? That's our multi-elerodes, right? Those are the little metal leads that let us read the neurons and then write

23:37to the neurons. So, here they did a highdensity multi-elerode array using CMOS technology. 26,000 platinum electrodes. What you can see over there, all of these little rectangles is an individual electrode, right? So, that can be individually tuned to have voltage, you know, 5 volts, -2 volts, whatever you want it to be. it can read the the electric field around it and it can write an electric field around it. Okay. So, and you can see the the sort of this is a I think it's a electron microscope and you can see the cell bodies and all the dendrites and all of the connections that are just sort of growing through that multi multi-elerode array. So, when I have a connection like

24:18a little axon that's connected from neuron A to B, I can follow that signal with my electrodes. Very very cool. Right. It looks like a map of LA from the sky. >> Yeah. Yeah, it really does. Like you the Spanish are very good at gridding and that's what that's what this looks like. If if you want if you're in Barcelona, it also looks like that, you know. >> Um >> and out of the 26,000 platinum electrodes, >> there's only 1024 independent channels >> that are active. >> Okay, >> so they can pick and choose which ones they want to read through, right? So that that's again a huge thing. And one of the incredible things is that the latency between reading and then making a computation to figure out what to write, right? Because I'm going to read

24:59the the the activity from the neurons, then I'm going to uh I don't know, I guess like see what the game state of of Pong is or Doom is and then write back to the neurons and give them feedback. They got it down to 5 milliseconds. That's such a huge >> which is which is quite a small latency. Yes. >> If you really think about it, >> that is inc. And and if we're trying to mimic the brain, we need that latency as close to zero as possible. >> Exactly. Because for us, our latency is around that. Right. >> Right. Um one of the common things that we think about is like our our eyes are about 60 frames per second is the top level of how many, you know, little pictures it takes every second and

25:41relays back to our brain. And so 60 frames, let's just say 50 frames per second cuz I want to make my math simpler. Yes. Right. So 50 frames per second that's about 20 milliseconds >> is the is the refresh rate >> of my eye to the brain. Right. And this is going down to 5 milliseconds. So it's it's even lower than that. It's that's the speed at which neurons talk. The action potential which is this thing that I was telling you about how when the neuron turns off it actually immediately turns off right after it turns on and off and that action potential takes about one millisecond. So getting it down is mimicking the sort of computational latency that the brain already has and what these neurons in

26:21your dish are used to. >> Yes. >> Right. So you don't you don't have them like thinking harder >> than they need to. >> Than they need to and being which makes it more energy efficient. >> Yeah. So now let's look at the dish brain protocol. How do we play Pong with our video game >> with our DBP? >> Yes. Okay. So over here we've got in the middle our petri dish that has on the bottom of it this multi-elerode array. These are little tiny electrodes that are going to sense the neuron culture that is on top. The neuron culture on top is getting bathed with electrolytes with glucose to keep it alive. Um they can keep it alive for as long as 6