As described above, clusters of neurons responding to the same stimulus tend to exhibit phase-locked synchronized oscillatory activity at 40-60 Hz. (Subsequent reports have shown that this effect can occur over large cortical distances, between cortical areas, and even between cerebral hemispheres.) The authors speculate that the synchronization of activity in widely distributed cell assemblies serves to "bind" the perceptual image and create the experience of "vivid visual awareness." In developing this theory, they correlate the neurobiological data to psychophysiological data on visual processing. Visual perception has traditionally been broken into two phases, an initial rapid parallel processing, thought to reflect "hard wired" analysis of simple features and elements, followed by a slower serial phase of analysis. The former process does not elicit "vivid awareness." However, in the latter phase, termed "focal attention," selected aspects of the visual scene are interpreted