Would anyone please link directly to the pdf of the paper so I can see for myself how they're keeping the mice awake?

The typical way is for them to put the mice in a position such that it's impossible for them to fall asleep without falling into water. All that this proves is that extended stress leads to lost neurons, not necessarily the sleep loss.

People often cite the "Fatal Familial Insomnia" disease as evidence of lack of sleep's ill effects, but they neglect to point out that the "insomnia" part is sometimes not observed in patients who then die anyway. So the sleep loss is apparently unrelated to the death.

There doesn't seem to be any conclusive evidence linking sleep loss to neurodegeneration. It's seemingly just something that people want to believe in absence of evidence.