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On the validity of electric brain signal predictions based on population firing rates
Fig 6
Effect of neuron and synapse heterogeneity on the variability of single-cell LFP kernels.
A: A population of cortical pyramidal neurons (morphologies depicted in shades of light gray and soma locations as black dots) receives synaptic input from a presynaptic population. Each incoming axon forms, in total, 
connections with different postsynaptic neurons. The strength J of each synapse is randomly drawn from a lognormal distribution. The synaptic time constant 
and the synaptic delay are drawn from normal distributions (graphs to the left). The vertical position of each synapse is drawn from the segment locations of the cells weighted by a normal distribution (green curve to the right). Some exemplary synapse positions are plotted on the postsynaptic population as green dots. Vertical soma positions are drawn from a capped normal distribution (black curve to the right). Horizontal soma positions are uniformly distributed on a disc within radiusRpop. The LFP response to an activation of all 
synapses of a single incoming axon is calculated for different cortical depths (dark red dots). The EEG response outside the head, directly above the population, is calculated using a simple spherical head model. For each parameter configuration, we generate 100 single-cell kernels resulting from different random realizations of neuron and synapse parameters. Each of these kernels describes the postsynaptic LFP (EEG) response to the firing of a different presynaptic neuron. B–D: LFP and EEG responses for different synaptic target zones (B: apical; C: basal; D: uniform). Gray: single-cell kernels. Black: population kernel. The “basal input” case is used as the “default case” throughout this study. E: Mean (solid curves) and standard deviation (bands) of the maximum LFP deflection at different cortical depths for different synaptic target zones (see legend). See Methods for details on the model and parameter values.
doi: https://doi.org/10.1371/journal.pcbi.1012303.g006