There were a couple parallel sub-discussions earlier this week, but no mention of spaced repetition:

Training exercise boosts brain power, Johns Hopkins researchers say | https://news.ycombinator.com/item?id=15508714 (Oct 2017, 138 comments)

>pdog: Do you know the best exercise for your brain? Actual exercise

>JamesBarney: I hit dual n back pretty hard trying to improve my IQ

https://www.gwern.net/DNB-meta-analysis