Modeling unitary fields and the single neuron contribution to local field potentials in the hippocampus

Large networks of neurons are often modelled by point neurons which require less computation time and resource expense than morphologically accurate models. However, calculating local field potential (LFP) activity of such neurons poses a challenge because individual point neurons do not produce spatially-distributed currents, which are necessary to compute LFPs. On the other hand, LFP recordings are relatively simple and commonly used for gathering the data from the brain tissue both in research and for medical purposes, making the understanding of LFP signals of crucial importance. In the present study, we calculate the field generated by single cells activity (uLFP) in the hippocampus in vitro. We reproduce experimental results for hippocampal basket cells, showing inhibitory uLFP distribution within hippocampal layers. Next, we calculate the unitary field generated by two morphologically reconstructed CA3 pyramidal neurons. We show that in the slice, excitatory uLFPs are of smaller amplitude than inhibitory uLFPs. Furthermore, we show how that uLFPs of pyramidal cells are masked by inhibitory uLFPs, which might create the illusion that the inhibitory field is generated by pyramidal cells. We propose that the results of our model might form the basis of a method to compute the LFP, which could be applied to point neurons for each cell type, thus providing a simple biologically-grounded method to calculate LFPs from neural networks.