For some reason, my last three patients with whom I have done EMDR have preferred knee-tapping. (They each report difficulty, when trying to follow the moving fingers, and maintaining concentration on the the target image, which is primarily visual).
I am noticing varying degrees of eye-movements, through closed eyelids, with these patients. This has me wondering if, perhaps, the underlying physiological mechanism might turn out to be mediated by eye-movements after all. Otherwise, it is difficult to understand the connections with REM and the earlier work you have just reported on the relation between eye-movements and cognitive processes.
Have others observed the contemporaneous eye- movements with tapping? with auditory clicking?
With these three patients, the effect of EMDR has been as powerful and in the other cases I have treated with eyeball manipulation.