Interesting new paper about tACS and peak alpha :
Transcranial alternating current stimulation (tACS) was shown to modulate brain oscillation, cortical excitability and behaviour. This technique allows for the direct perturbation of brain oscillation such as the EEG alpha wave (8–12 Hz). In aging, there is correlation between the decrease in alpha activity and the profound cognitive and motor impairments. Studies suggest a state-dependent effect of tACS on alpha activity: upregulation of alpha oscillations only occurs in conditions of low alpha power (e.g. in the elderly).
Remember, the foc.us v3 is the only brain stimulator that has rippled current designed to increase your peak alpha.