recently i've came across an interesting TEDx talk on falling asleep. Jim Donovan presents there his way of falling asleep by generating certain frequency, waiting for brain to “tune” to it, and then slowing it down up to a point you fall asleep.
the mechanisms behind “tuning” to such a pattern is called frequency following response. if you think about it, it is logical. brain has evolved to quickly detect and lock on patterns. this is how we learn new things – we notice new, repeating patterns (while sometimes our brains make a wrong associations, detecting patterns in randomness, it overall yield good results). once detected, brain follows the pattern.
FFR seems to be an interesting byproduct of pattern recognition machinery in brain. after learning about FFR it became clear to me why seesaws tend to make you sleepy (especially children) and why hammock can serve the same purpose. it's all about damping oscillations.