# Cortex-wide spatiotemporal motifs of theta oscillations are coupled to freely moving behavior

## TL;DR

This study reveals that theta oscillations in the mouse cortex form organized patterns linked to movement and sensory processing.

## Contribution

The discovery of bilaterally-symmetric spatiotemporal theta modes across the neocortex is novel.

## Key findings

- Theta oscillations form a dominant divergent wave from the retrosplenial cortex, correlated with mouse speed.
- Secondary spiral theta waves in the somatosensory cortex drive phase resets during null spikes.
- These structured waves may support large-scale phase-coding of information in the cortex.

## Abstract

Multisensory information is combined across the cortex and assimilated into the continuous production of ongoing behavior. In the hippocampus, theta oscillations (4–12 Hz) radiate as large-scale traveling waves, and serve as a scaffold for neuronal ensembles of multisensory information involved in memory and movement-related processing. An extension of such an encoding framework across the neocortex could similarly serve to bind disparate multisensory signals into ongoing, coherent, phase-coded processes. Whether the neocortex exhibits unique large-scale traveling waves distinct from that of the hippocampus, however, remains unknown. Here, using cortex-wide electrocorticography in freely moving mice, we find that theta oscillations are organized into bilaterally-symmetric spatiotemporal “modes” that span virtually the entire neocortex. The dominant mode (Mode 1) is a divergent traveling wave that originates from retrosplenial cortex and whose amplitude correlates with mouse speed. Secondary modes are asynchronous spiral waves centered over primary somatosensory cortex (Modes 2 and 3), which become prominent during rapid drops in amplitude and synchrony (null spikes) and which underlie a phase reset of Mode 1. These structured cortex-wide traveling waves may provide a scaffold for large-scale phase-coding of information across the cortex.