Researchers have grown brain cells in a lab that have learned to play the 1970s tennis-like video game, Pong.

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Writing in the journal Neuron, Dr Brett Kagan, of the company Cortical Labs, claims to have created the first ''sentient'' lab-grown brain in a dish.

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The mini-brains are likely to become more complex as the research progresses - but Dr Kagan's team are working with bioethicists to ensure they do not accidentally create a conscious brain, with all the ethical questions that would raise.

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...Prof Karl Friston, of University College London, who is working with Dr Kagan, says: "The mini-brain learned without it being taught and so is more adaptable and flexible."

Russian President Vladimir Putin has reignited fears that he is about to use nuclear weapons in Ukraine following a viral video and a defense analyst's comments.