Simulation setup.

<p>A. Input spike trains are either generated independently for each cell (uncorrelated input), or chosen from a common pool (correlated input: every two cells share a fraction of inputs). B. Model cells (red: L3 pyramidal cell, green: L4 stellate cell, blue: L5 pyramidal cell) are placed with constant planar density on a disc of radius , in this example with the recording electrode at the population center. Electrode positions shown as black dots. C. The population LFP is a sum of contributions from cells at different distances . The dependence of the amplitude of the population LFP on the population radius serves to define the spatial reach (see text). The correlations between inputs give raise to correlations between single-cell LFP contributions. D. The synapses used in simulations yield a flat power spectrum of input current, but because of the frequency-dependence of single-cell <i>shape functions </i> and <i>population-averaged coherence </i> (see text), the resulting power spectrum of the population LFP is not flat (E). This LFP filtering effect will be present for any synapse type, such as the exponential synapse which in addition yields non-flat power spectrum of the input current (dashed curves in D, E).