Place coding + rate coding — how the neurons “see” Pong

36:19neuron fired was the loudness. >> In this case, >> Mhm. >> how are we actually um if we go back to photo 14. Yes. Actually, >> how are we actually going to use that sensory cortex, the eight electrodes that we're trying to write in our information? How are we going to use place and rate coding to inform my petri dish brain about the state of the game? That's the key right? >> What they did was they said something very interesting. The um where the ball is or where the um sorry where the paddle is. >> Yes. >> Is going to be my place.

37:00>> Mhm. >> Okay. So, if my paddle is lower on the screen, I'm going to fire the electrodes on the left. I'm going to make the left electrodes give some electricity to my brain. If the paddle is up on the screen, I'm going to give the right electrodes. Okay, so now I've got place. What's the other thing I need to code in? That's the distance to the ball. How close is the ball? How close is it getting? Right? And so, for that, they use frequency. >> They went all the way from four hertz to 40 Hz. Four hertz means it's very far away. 40 Hz means it's getting close. You need to you need to figure out which way to go. >> Right. >> And and the idea here is is we are

37:41basically creating a translation between what we experience as a visual input >> where we can do the rate and place just through our visual input. >> That's right. into an electrical input such that but that is uh regional >> as a means to create an extra layer of like degree of freedom in in in encoding more data in what is a relatively flat kind of system. >> Yeah, exactly. And we need to be able to give those neurons in my petri dish both of these pieces of information. Right. And one thing I do want to be clear here is the neurons in this petri dish are not directly seeing the game like we

38:23are. This is kind of what I'm trying to >> right >> poke at. >> Yes. They're not seeing the game like humans do. Instead, they're sort of seeing the game based on the paddle's point of view in some sense. It's like where am I >> if I'm the paddle and also how far away is the ball, >> right? >> Those are the things and the only res the resolution is only like eight pixels in some sense, right? >> But from that they're trying to make this petri dish play pong. Okay. So the other thing that we need to think about is fine now we've got a read and write mechanism. >> Yes. >> Now we need a training mechanism. >> Right. >> Right. >> Cuz now all of a sudden I mean we're

39:03telling the petri dish the state of the game and we have some way of reading what the petri dish wants to do >> which is move the paddle up or move the paddle down. How does the petri dish know whether it's doing well or not? >> Yes. >> Right. The challenge is actually quite non-trivial because in the brain, how do we get a reward? You know, we we feel happiness, maybe we