Comparing Theravada and Tibetan meditation

In Thompson's paper "Dreamless sleep, the embodied mind and consciousness," one study measured experienced Theravadan and Tibetan meditators during deep, slow-wave sleep and found they had 20-25% higher incidence of gamma wave activity in the parietal-occipital region. So this sort of gamma wave activity is not limited to Tibetan style meditation, since both styles include both concentrative and receptive meditations.

This study discussed these two kinds of meditation, calling them focused or distributed. It noted that both types in Theravada produced more the relaxation response, whereas both types in the Tibetan produced more the arousal response. They suggest that it therefore behooves us to not use the focused (concentrative) and distributed (receptive) categories in this research, since both styles were studied from each tradition. They further suggest that the relaxed and arousal categories are more indicative of the two traditions.
Which may speak more to the emphasis of the traditions. The initial post study (at least the abstract, don't have the actual study) didn't talk in terms of gamma and alpha waves but in terms of parasympathetic (relaxation) and sympathetic (arousal) responses. Granted there are more alpha waves in the former and more gamma waves in the latter. But again, this may indicate the different emphasis of the traditions instead of supposing that more gamma waves in itself is somehow 'better.' Recall that concentrative practices tend to elicit more of the ego ideal, which often leads to metaphysical interpretations. In this case Epstein refers to the Tibetan concentrative practices and not the Theravada concentrative practices.

And don't forget the study Thompson cited, which is also new and notes both traditions produce gamma waves in deep sleep. Thompson noted that producing gamma waves in the deep sleep is the result of doing meditative practices while not sleeping of the type that induces consciousness without an object. Both Theravada and Tibetan practices accomplish this. So again, this may be more a traditional emphasis. It seems a lot more study is needed to ascertain the postmetaphyiscal meaning of the neuroscientific data. Especially since laughing also produces gamma waves, and that requires just a sense of humor and no special meditative skill. Lots of folks laugh a lot and have not in the least developed brain synchrony or higher abstract functions.