Cortical traveling waves in time and space: Physics, physiology, and psychology

The advent and widespread adoption of diverse widefield imaging techniques across multiple spatial resolutions has demonstrated that cortical activity often propagates as waves structured in both time and space. This realization allows neuroscientists to draw on a rigorous theoretical framework developed in wave physics to complement and inform the rapid neuroscientific advances shedding light on the physiological mechanisms and psychological implications of cortical wave dynamics. In support of this synthesis, we review some of the core concepts that underpin wave physics and consider how they relate to experimental studies of cortical wave physiology and psychology. We show how cortical waves emerge naturally from the physical embedding, connection topology, and intrinsic dynamics of the cortex; examine work demonstrating that spontaneous macroscopic waves spanning the entire cortex serve to synchronize disparate regions positioned at distinct levels of cortical processing hierarchies; and consider how stimulus-evoked waves encode information about both perceived stimuli and behavior while providing a mechanism for the integration of feedforward and feedback signals that underpins predictive coding. The ubiquity of cortical waves, which have been observed in different species, across different states, and with different recording techniques, underscores their importance for cortical function. A comprehensive understanding of their significance will depend on a combination of physical, physiological, and psychological approaches.