Frequency dependence of signal power and spatial reach of the local field potential

TL;DR

This study uses biophysical modeling to analyze how synaptic input correlations influence the frequency dependence and spatial reach of local field potentials, revealing that low-frequency signals are less local and spread further than high-frequency signals.

Contribution

It provides a quantitative interpretation of the frequency dependence of LFPs, highlighting the impact of synaptic correlations on signal spread and frequency characteristics.

Findings

Low-frequency LFP components are boosted by synaptic input correlations.

Low-frequency signals have a larger spatial reach and are less local.

High-frequency LFPs are more confined and less affected by volume conduction.

Abstract

The first recording of electrical potential from brain activity was reported already in 1875, but still the interpretation of the signal is debated. To take full advantage of the new generation of microelectrodes with hundreds or even thousands of electrode contacts, an accurate quantitative link between what is measured and the underlying neural circuit activity is needed. Here we address the question of how the observed frequency dependence of recorded local field potentials (LFPs) should be interpreted. By use of a well-established biophysical modeling scheme, combined with detailed reconstructed neuronal morphologies, we find that correlations in the synaptic inputs onto a population of pyramidal cells may significantly boost the low-frequency components of the generated LFP. We further find that these low-frequency components may be less `local' than the high-frequency LFP components in the sense that (1) the size of signal-generation region of the LFP recorded at an electrode is larger and (2) that the LFP generated by a synaptically activated population spreads further outside the population edge due to volume conduction.