1. There is no control group. Since people get better with cognitive tests with practice, we don’t know whether these improvements were due to the treatment or just the normal practice effect. (Though if I were a betting person, my money is on the latter.)
2. Cognitive tests are not noiseless. The same person may vary by a few points between repeated tests. The modest improvements on most tests found here might not be above this noise floor.
3. The most impressive result (memory) is almost certainly regression to the mean. That is, the group did unusually poorly on this task in the first session by chance, then they performed more typically in the second, which looks falsely like a big improvement.
Basically, I think this paper provides no meaningful evidence of cognitive improvement in humans. I can’t speak about the mice stuff, that might be fine.