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Abstract

Scale-free dynamics, with a power spectrum
following P alpha f -beta, are an intrinsic feature of many
complex processes in nature. In neural systems,
scale-free activity is often neglected in electrophysiological
research. Here, we investigate scale-free
dynamics in human brain and show that it contains
extensive nested frequencies, with the phase of lower
frequencies modulating the amplitude of higher
frequencies in an upward progression across the
frequency spectrum. The functional significance of
scale-free brain activity is indicated by task performance
modulation and regional variation, with
beta being larger in default network and visual cortex
and smaller in hippocampus and cerebellum. The
precise patterns of nested frequencies in the brain
differ from other scale-free dynamics in nature, such
as earth seismic waves and stock market fluctuations,
suggesting system-specific generative mechanisms.
Our findings reveal robust temporal structures
and behavioral significance of scale-free brain
activity and should motivate future study on its physiological
mechanisms and cognitive implications.