Theta and alpha oscillations are traveling waves in the human neocortex

Abstract

Human cognition requires the coordination of neural activity across widespread brain networks. Here we describe a new mechanism for large-scale coordination in the human brain: traveling waves of theta and alpha oscillations. Examining direct brain recordings from neurosurgical patients performing a memory task, we found that contiguous clusters of cortex in individual patients showed oscillations at specific frequencies in the range of 2 to 15 Hz. These clusters displayed spatial phase gradients, indicating that individual oscillation cycles moved across the cortex at ~0.25-0.75 m/s. We found that traveling waves were relevant behaviorally because their propagation correlated with task events and was more consistent during good performance. Traveling waves showed a correlation between propagation speed and temporal frequency, which suggests that they propagate across the cortex following principles of phase-coupled oscillatory networks. By demonstrating that theta and alpha traveling waves are widespread and behaviorally relevant, our results suggest a broad role for brain oscillations in supporting cortical connectivity by organizing neural activity across space and time.