DishBrain (in-vitro neural culture)

~800,000 human iPSC-derived or mouse cortical neurons are plated onto a high-density multi-electrode array (HD-MEA). The DishBrain system (Kagan et al., 2022, Neuron) embeds the culture in a simulated game of Pong: electrode stimulation encodes ball position and side; the recorded neural firing pattern drives paddle movement. Motivated by the free-energy principle — cells prefer predictable stimulation over white noise — the culture learns to rally the ball within five minutes of real-time play. No explicit training algorithm runs; the biology self-organizes. The substrate is neurons-in-a-dish, making this the only entry where the substrate is alive and may be sentient. Speed: minutes to learn; milliseconds per action (neural firing rate). Capacity: closed-loop sensorimotor tasks; ~800,000 neurons, ~22,000 electrodes.