Preservation and changes in oscillatory dynamics across the cortical hierarchy

Theta (2-8 Hz), Alpha (8-12 Hz), beta (12-35 Hz) and gamma (>35 Hz) rhythms are ubiquitous in cortex. But there is little understanding of whether they have similar properties and functions in different cortical areas because they have rarely been compared across them. We record neuronal spikes and local field potentials simultaneously at several levels of the cortical hierarchy in monkeys. Theta, alpha, beta and gamma oscillations had similar relationships to spiking activity in visual, parietal and prefrontal cortex. However, the frequencies in all bands increased up the cortical hierarchy. These results suggest that these rhythms have similar functions inhibitory and excitatory across cortex. We discuss how the increase in frequencies up the cortical hierachy may help sculpt cortical flow and processing. Significance statement Phase-coupling in alpha/beta and gamma frequency ranges between cortical areas is often viewed as a means to shape brain-wide communication. However, systematic frequency differences between communicating areas are typically not considered, but equally important. Here we show that alpha/beta and gamma oscillations are of systematically higher frequency ascending the cortical hierarchy. This presents a fresh view on a widely studied topic. It has important implications in shaping cortical communication and helps explain widely observed phenomena.