How could brain imaging NOT tell us about consciousness?

Revonsuo argues that current brain imaging methods do not allow us to 'disc over' consciousness. While all observational methods in science have limita tions, consciousness is such a massive and pervasive phenomenon that we can not fail tb observe its effects at every level of brain organization: molec ular cellular electrical, anatomical, metabolic, and even the 'higher level s of electrophysiological organization that are crucial for the empirical d iscovery and theoretical explanation of consciousness' (Revonsuo, this issu e). Indeed, the first major discovery in that respect was Hans Berger's finding that scalp EEG is massively different between waking and deep sleep, alrea dy seven decades ago. We now have perhaps a dozen sophisticated methods for monitoring consciousness-I-elated activity at multiple levels of brain obs ervation. Theoretical progress has come quite rapidly Recently, E.R. John a nd colleagues have made fundamental findings using Quantitative EEG, showin g consistent brainwide changes as a result of several types of general anae sthetics (John et. al., in press). John (in press) has proposed a neuronal 'field theory' to account for those results. Another promising new method i nvolves frequency-tagging of competing stimuli, allowing us to follow the a ctivity of billions of neurons synchronized to particular conscious stimuli , always compared to very similar unconscious input (e.g. Tononi et al., 19 98; Srinivasan ef al., 1999). A fundamental theoretical account of such res ults has been provided by Tononi & Edelman (1998). Such results and theory are in broad agreement with the cognitive theory proposed by Baars (1983; 1 988; 1997; 1998).