Owing to the bidirectionally-constrained relationship between single neurons and their population product, the time lags between spikes of neurons have important functional consequences. First, despite variable running speed of the rat, place cells continue to represent the same positions and distances in the same environment because the oscillation frequency of place cells increases in proportion with the velocity, while time lags remain essentially the same (Diba and Buzsáki, 2008; Geisler et al., 2007). Second, the duration of the theta cycle (120–150 msec in the rat) sets a natural upper limit of distance coding by theta-scale time lags (~50 cm for neurons in the dorsal hippocampus; Dragoi and Buzsáki, 2006; Maurer et al., 2005), as reflected by the sigmoid relationship between the theta time lags of neuronal spikes and distance representations (Fig. 6E; Diba and Buzsáki, 2008). The behavioral consequence of the sigmoid relationship is that objects and locations > 50 cm ahead of the rat are initially less distinguishable from more distant landmarks, but as the animal approaches, they are progressively better resolved by the interleaved cell assemblies. Third, the
