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On the validity of electric brain signal predictions based on population firing rates

Fig 2

Illustration of the principle underlying the kernel method.

A: The postsynaptic perspective, where all incoming synaptic input to a postsynaptic cell is taken into account, and the time-dependent LFP contribution of the postsynaptic cell is calculated. The blue and red colors are used to illustrate positive and negative regions, respectively, of the LFP at a moment in time. The total population LFP V ( r , t ) is then the sum of all such single-cell contributions . This is the standard way of calculating LFP signals from neural simulations. B: The presynaptic perspective, where all outgoing synapses from a single cell are considered. For passive cells with static (no plasticity), current-based synapses, every action potential of a presynaptic neuron j will evoke the same postsynaptic currents, and hence, each action potential has a fixed LFP response . By taking into account all postsynaptic targets, the single-cell kernel can be calculated, and the single-cell LFP contribution can be found by convolving the single-cell kernel with the corresponding spike train of the presynaptic cell. The population LFP is again the sum of all single-cell contributions, and if this is done for all cells, and all external incoming synapses, the LFP calculated by these two approaches will be identical, under the assumptions listed above.

doi: https://doi.org/10.1371/journal.pcbi.1012303.g002