How large is a cell assembly, what is its duration (‘life time’) and what, exactly, does it represent in the cognitive or output domain? Does an assembly represent a feature, a figure or background, an object or concept, a thought process, a plan for immediate action, or even more complex processes? 2 Unfortunately, the very idea of identifying the neuronal correlates of such psychological constructs on the presumption that they must have clear boundaries, in correspondence with the neuronal substrates of their representation, is questionable. According to the ‘representational framework’ (Engel et al., 2001; Hebb, 1949; James 1890; Milner 1996; von Malsburg 1994), the way to identify cell assemblies is to present various stimuli to the brain (e.g., an object or aspects of an object) and examine the spatio-temporal distribution of the evoked neuronal responses (Hubel and Wiesel, 1962; Rieke et al., 1997).3 An implicit goal of such a strategy is to eventually explain how elementary attributes that are believed to comprise an object (e.g., color, shape, odor, sound, motion, etc) are bound together at the neuronal level so that
