The makers of brain-training apps and games claim their products can do everything from staving off cognitive decline to improving your IQ. But so far these claims have been met with mixed evidence.

Hardware 'A number of threads retracted from the brain' of Neuralink's first implant patient, but they say they're still 'beating my friends in games that as a quadriplegic I should not be beating ...

Some 2.3 million of U.S. adults older than 65 — more than 4% — have a diagnosis of dementia. But even without a diagnosis, a certain amount of cognitive decline is normal as age sets in.