Temporal coupling of field potentials and action potentials in the neocortex

Abstract

The local field potential (LFP) is an aggregate measure of group neuronal activity and is often correlated with the action potentials of single neurons. In recent years, investigators have found that action potential firing rates increase during elevations in power high‐frequency band oscillations (50–200 Hz range). However, action potentials also contribute to the LFP signal itself, making the spike–LFP relationship complex. Here, we examine the relationship between spike rates and LFP in varying frequency bands in rat neocortical recordings. We find that 50–180 Hz oscillations correlate most consistently with high firing rates, but that other LFP bands also carry information relating to spiking, including in some cases anti‐correlations. Relatedly, we find that spiking itself and electromyographic activity contribute to LFP power in these bands. The relationship between spike rates and LFP power varies between brain states and between individual cells. Finally, we create an improved oscillation‐based predictor of action potential activity by specifically utilizing information from across the entire recorded frequency spectrum of LFP. The findings illustrate both caveats and improvements to be taken into account in attempts to infer spiking activity from LFP.We examined the relationship between spike rates and local field potentials (LFP) in the rat neocortex, and we find that while 50–180 Hz oscillatory power correlates most consistently with firing rates of neurons, other LFP bands also carry spiking‐related information. We additionally find that spiking itself and electromyographic activity contribute to LFP power and that the ratio of excitatory to inhibitory activity also correlates with 50–180 Hz power. Finally, we create an improved oscillation‐based predictor of action potential activity by utilizing information from the entire LFP frequency spectrum at once.