News without the buzz: reading out weak theta rhythms in the hippocampus

Abstract

Local field potentials (LFPs) reflect the collective dynamics of neural populations, yet their exact relationship to neural codes remains unknown ¹ . One notable exception is the theta rhythm of the rodent hippocampus, which seems to provide a reference clock to decode the animal’s position from spatiotemporal patterns of neuronal spiking ² or LFPs ³ . But when the animal stops, theta becomes irregular ⁴ , potentially indicating the breakdown of temporal coding by neural populations. Here we show that no such breakdown occurs, introducing an artificial neural network that can recover position-tuned rhythmic patterns (pThetas) without relying on the more prominent theta rhythm as a reference clock. pTheta and theta preferentially correlate with place cell and interneuron spiking, respectively. When rats forage in an open field, pTheta is jointly tuned to position and head orientation, a property not seen in individual place cells but expected to emerge from place cell sequences ⁵ . Our work demonstrates that weak and intermittent oscillations, as seen in many brain regions and species, can carry behavioral information commensurate with population spike codes.