I feel like they probably could use another mammals neural cells and get similar results, but they use human cells because it'll get them attention - and that kind of rubs me the wrong way.
Whoever thought people would become Dr Frankenstein for the karma.
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Counterpoint: a major use case for this technology would be to experiment on human brain structures to research and hopefully cure neurological diseases like Alzheimer's. If you want to cure Alzheimer's in humans, you might as well use human brain cells from the start.
But yes, I agree that they're likely using human brain cells mainly because it's attention-getting.