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Mouse and human brain cells in a lab dish learn to play the video game Pong : Shots


A dish of living brain cells learned to play a 1970s arcade game pong.

About 800,000 cells linked to a computer gradually learned to sense the position of an electronic ball in play and control a virtual paddle, the team reports in the magazine Neuron.

The new achievement is part of an effort to understand how the brain learns and how to make computers smarter.

“We’ve made huge advances in silicon computing, but it’s still rigid and inflexible,” says Brett Kagan, study author and principal scientist at Cortical Labs in Melbourne, Australia. “That’s something we don’t see in biology.”

For example, both computers and humans can learn to make a cup of tea, Kagan says. But humans are able to generalize what they have learned in a way that a computer cannot.

“Maybe you’ve never been to someone’s house, but with a little digging and searching, you can probably make a decent cup of tea as long as I have the ingredients,” he says. But even a very powerful computer can hardly cope with this task in an unfamiliar environment.

So Cortical Labs tried to understand how living brain cells acquire such intelligence. And Kagan says the Pong experiment was a way for the company to answer a key question about how a network of brain cells learns to change its behavior:

“If we let these cells know the outcome of their actions, can they actually change in some purposeful way,” says Kagan.

To find out, scientists used a system they developed called DishBrain.

This scanning electron microscope image shows a neural culture growing on a high-density multielectrode array. This system allowed the researchers to train neurons to play the video game Pong.

Cortical Labs

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Cortical Labs

This scanning electron microscope image shows a neural culture growing on a high-density multielectrode array. This system allowed the researchers to train neurons to play the video game Pong.

Cortical Labs

A layer of living neurons is grown on a special silicon chip at the bottom of a thumb-sized dish filled with nutrients. The chip, which is connected to a computer, can both detect electrical signals generated by neurons and deliver electrical signals to them.

To test the cells’ ability to learn, the computer created a game of pong, a two-dimensional version of table tennis that became iconic as one of the first and simplest video games.

Pong is played on a video screen. The black rectangle defines the table and the white cursor represents each player’s paddle, which can be moved up or down to intercept the cue ball.

In the simplified version used in the experiment, there was one paddle on the left side of the virtual table, and the ball moved away from the other sides until it avoided the paddle.

To let the brain cells play the game, the computer sent them signals that told them where the bouncing ball was. At the same time, he began to control the information coming from the cells in the form of electrical impulses.

“We took that information and let it influence the game of Pong they were playing,” Kagan says. “So they can move the oar.”

At first the cells did not understand the signals coming from the computer and did not know which signals to send in the other direction. They had no reason to play the game either.

So the scientists tried to motivate the cells with electrical stimulation: a beautifully orchestrated burst of electrical activity when they got it right. When they got it wrong, the result was a chaotic stream of white noise.

“When they hit the ball, we give them something predictable,” Kagan says. “When they missed that, they got something that was completely unpredictable.”

The strategy was based on Art The principle of free energy, which states that brain cells want to be able to predict what is happening in their environment. Thus, they would choose a predictable stimulus over an unpredictable one.

The approach worked. The cells began to learn to generate patterns of electrical activity that moved the paddle in front of the ball, and gradually the rallies became longer.

Brain cells have never gotten so good at pong. But interestingly, human brain cells seem to reach a slightly higher level of play than mouse brain cells, Kagan says.

And the level of play was remarkable, given that each grid contained fewer cells than a cockroach’s brain, Kagan says.

“If you saw a cockroach playing pong and it was able to hit the ball twice as often as it missed it, you would be very impressed with that cockroach,” he says.

The results hint at a future in which biology helps computers become smarter by changing the way they learn, Kagan says.

But this future is probably still a long way off, he says Steve M. PotterAdjunct Professor, Georgia Institute of Technology.

“The idea of ​​a computer that has some living components is exciting, and it’s starting to become a reality,” he says. “However, the kinds of learning these things can achieve are pretty rudimentary right now.”

Even so, Potter says that a system that allows cells to learn Pong could be a great tool for research.

“It’s kind of a semi-living animal model that can be used to study all kinds of mechanisms in the nervous system, not just for learning,” he says.

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