Sensory encoding and memory retrieval are coordinated with propagating waves in the human brain

Complex behavior entails a balance between taking in sensory information from the environment and utilizing previously learned internal information. Studies on mice show that the brain continually alternates between outward and inward cognitive modes every few seconds, accompanied by stereotyped cascades of neuronal spiking. Our analysis of large fMRI datasets revealed a similar mechanism in humans. Human brain activity was punctuated every several seconds by coherent, propagating waves emerging in the exteroceptive sensorimotor regions and terminating in the interoceptive default mode network. As in mice, these waves in human fMRI are accompanied by phase-specific enhancements in sensory information encoding and memory retrieval. These findings suggest a conserved feature of mammalian brain physiology that bears directly on the integration of sensory and mnemonic information during everyday behavior.