prediction of spike timing from the other variables should have an optimum time window. By varying the analysis window experimentally, the best prediction of the spike timing of single hippocampal neurons from the activity of other neurons was found when spiking of peer neurons was assessed in 10 to 30 msec epochs (Figure 2; Jensen and Lisman, 1996; 2000; Harris et al., 2003; Kelemen and Fenton, 2010; Lansner, 2009). When two cells with distinct place fields (O’Keefe and Nadel, 1978) were examined their activity was associated with the spiking of distinct peers and the formed assemblies could alternate in a fast sequence (Figure 2A). The participation of individual assembly members from trial-to-trial can vary much more than the whole assembly (Pouget et al., 2000). Given the similarity between the temporal window of the assembly life time and the time constant of pyramidal cells, the postulated physiological goal of the cell assembly is to mobilize enough peer neurons so that their collective spiking activity can discharge a target (reader) neuron(s). Due to anatomical constraints, various combinations of upstream cells, active in a short time window, converge onto different reader neurons in the target layer (Figure 1C). Whether different constellations of spiking
