Fig. 2.

Poisson fit to experimental data from a moderately large open-field environment (Fenton et al. 2008). The data was recorded from place cells in the CA1 as a rat explored a cylinder with a 68-cm diameter and a chamber whose floor had dimensions 150 × 140 cm². Place cells had multiple, irregularly spaced place fields and showed global remapping between environments. We fit the experimental data with the Poisson distribution (Eq. 1), using the respective areas for the cylinder and chamber floor and the place field density, λ = 1.65 m⁻². This parameter implies that ∼50% of CA1 place cells would be silent in a 0.4-m² region, which is consistent with the 30–50% range found experimentally (Guzowski et al. 1999; Vazdarjanova and Guzowski 2004; Wilson and McNaughton 1993). A and B: the Poisson distribution captures the general trend of the data. Since the number of silent cells was not measured in the experiment, we extrapolated the probability that a cell has no fields from the experimental data using the Poisson distribution with λ = 1.65 m⁻². C: the model also predicts the distance from one place field to the closest place field of the same cell, which is approximated by the Rayleigh distribution (dashed red curve; Eq. 15). To take into account the close boundaries of the chamber, which lower the probability of small distances, the solid red curve was generated from numerical simulations in which the place fields of 150,000 cells were distributed throughout the chamber floor according to the Poisson distribution. Additional statistics are given in Table 1.