The theta time compression mechanisms constrain how space and memory are represented, because the delays between the place cells limit the number of cell assemblies in the theta cycle54,86. In turn, the duration of the theta cycle limits the distances that can be linearly resolved by the sequential activity of neurons in a given environment, resulting in a sigmoid relationship between theta-scale time lags of spikes and distance representations by place cell pairs75,79,86 (Fig. 5d). As a result, upcoming locations that are more proximal to the animal are given stronger representation within a given theta cycle, with poorer resolution of locations in the distant future86. The size of place fields and grids of individual neurons and the distance representations of neuron pairs scale with the size of the environment3,31,86. In a way, the theta-nested assembly organization can be conceived as a ‘zooming’ mechanism, which provides a relatively coarse resolution of a large environment but an increasingly finer spatial resolution in smaller environments, with more neurons devoted to a given area of space, increased co-firing among cells in each theta cycle
