The tripartite relationship between global theta frequency ftheta, the oscillation frequency of single neurons fo and the distance-related, theta time-scale temporal lags of spikes (time ‘compressed’ sequences) has important consequences on the assembly organization of hippocampal neurons. First, the difference in oscillation frequency between the population (ftheta) and active single neurons generates an interference pattern, known as ‘phase precession’ of place cells (O’Keefe and Recce, 1993) so that the distance traveled from the beginning of the place field can be instantly inferred from the theta phase of the place cell spikes (Fig. 6D; Dragoi and Buzsáki, 2006; Skaggs et al., 1996). Second, the slope of the phase precession defines the size of the place field (O’Keefe and Recce, 1993; Maurer et al., 2005). Neurons with identical place fields will fire at the same phase, thus the observer neurons will classify them as members of the same assembly. Third, the field size (i.e., the ‘lifetime’ of activity) is inversely related to the oscillation frequency of the neuron. As a result, neurons which oscillate faster have smaller place fields and display steeper
