By no means my area of expertise, but a quick glance suggests:
The experimenters set up a system that could detect slow-wave (SW) fluctuations in brain activity. They used trans-cranial magnetic stimulation (electro-magnets on the scalp) to "augment" this SW activity. This seems to have improved memory, measured by some specific learning task they set for the participants.
Trans-cranial magnetic stimulation is becoming popular in trans-human type circles. Apparently it's becoming feasible to do at home with cheap off the shelf components. However, of course, the long term effects and side effects are poorly understood.
This particular experiment used 16 participants (only three of whom were female, for some daft reason) so we can't draw any firm conclusions from this.
Apologies, you're quite right, they're using "transcranial alternating current stimulation" a.k.a. tACS during sleep. Now I'm at my desktop I can read the paper, and see that they applied direct current during task training (discovery of "hidden targets in static images") using the "StarStim R32 simultaneous EEG/Stimulation device", and their own tACS system during sleep.
ECT(Electroconvulsive therapy) is already a thing - it is used for various treatments for depression and seizures. It consists of small electric currents passing through the brain which is very similar to brain stimulation, the only difference is that he first one is a medical procedure while the latter is, as of now, more like a brain hack. I wouldn't recommend anyone doing it without knowing the risks involved.
I don't think it's accurate to describe ECT as using small electric currents. The very name says that the procedure induces convulsions.
From Wikipedia: "ECT is often used with informed consent as a last line of intervention for major depressive disorder, mania, and catatonia. ECT machines have been placed in the Class II category (special controls) by the United States Food and Drug Administration (FDA) since 1976." (Emphasis mine.)
The experimenters set up a system that could detect slow-wave (SW) fluctuations in brain activity. They used trans-cranial magnetic stimulation (electro-magnets on the scalp) to "augment" this SW activity. This seems to have improved memory, measured by some specific learning task they set for the participants.
Trans-cranial magnetic stimulation is becoming popular in trans-human type circles. Apparently it's becoming feasible to do at home with cheap off the shelf components. However, of course, the long term effects and side effects are poorly understood.
This particular experiment used 16 participants (only three of whom were female, for some daft reason) so we can't draw any firm conclusions from this.