Dreamless sleep and consciousness

In Thompson's "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. This indicates that they are maintaining some phenomenal, lucid awareness during deep sleep. Thompson still maintains though that this awareness is the pre-personal lived body and not the metaphysical witness maintained by the traditions. And this skill can be trained via meditative discipline to experience this 'consciousness without an object' while not in deep sleep but certainly deep meditation. That is, the training one does through meditation that elicits consciousness without an object while not sleeping provides the basis for maintaining such an awareness while in deep sleep, which is what Thompson is asserting through the study.