Information content and interpretation of CSD non-trivially depends on array density.

Abstract

<i>Objective.</i>We aim to determine whether commonly-used current source density (CSD) estimation techniques provide valid results when used with recordings from the latest generation of high-density arrays and how the density affects signal interpretation.<i>Approach.</i>We first develop an analytic formulation for the contributions of Gaussian current sources to an estimated CSD as a function of current source position and array density. We then simulate local field potential recordings in a biophysically detailed model of a subvolume of rat somatosensory cortex, and compare estimated current source densities to the ground truth current densities averaged over relevant tissue volumes.<i>Main results.</i>Commonly used methods to estimate the CSD can produce spurious results when the inter-electrode spacing is small relative to the width of the current source, confusing sources and sinks. For high-density recording electrodes, the estimated CSD diverges from the volume-averaged ground-truth current distribution that the CSD estimation method attempts to reconstruct. Both confusion of sinks and sources and amplification of local current fluctuations play a role in this divergence. Careful choice of CSD reconstruction parameters can be used to preferentially reveal the information content on a local or higher-level scale.<i>Significance.</i>Our results shed light on high-spatial-frequency oscillations observed in estimated current source densities from<i>in vivo</i>experiments. Care must be taken when choosing a reconstruction method and interpreting the results from high density arrays, but proper parameter tuning allows to focus on specific information-of-interest. In addition, it was found that detailed network models, including active conductances and background noise, can be necessary to accurately simulate high-frequency current fluctuations.