That's how small the high quality input to your neural network is. All your smart neurons start their inputs there (let's skip hearing for a moment). Every tim

That's how small the high quality input to your neural network is. All your smart neurons start their inputs there (let's skip hearing for a moment). Every time you did math it worked on neurons with their roots at this small bunch in the visual cortex. It's a tool for reusing training data. When you move your eyes around same neurons are fed new data samples. It's basically same trick that convolutional neural nets use.