Power-Law Scaling in the Brain Surface Electric Potential

TLDR

"The PSD of cortical potentials follows a power‑law from 80–500 Hz with a conserved scaling index across subjects and cortical areas; its amplitude rises with local activity while the spectral shape and a characteristic knee remain constant, indicating activity‑dependent fluctuations in an underlying power‑law process and suggesting a new asynchronous, scale‑free paradigm complementary to rhythmic activity." That's long but okay. Must be one sentence. Ensure no semicolons? We can use commas.

Abstract

Recent studies have identified broadband phenomena in the electric potentials produced by the brain. We report the finding of power-law scaling in these signals using subdural electrocorticographic recordings from the surface of human cortex. The power spectral density (PSD) of the electric potential has the power-law form from 80 to 500 Hz. This scaling index, , is conserved across subjects, area in the cortex, and local neural activity levels. The shape of the PSD does not change with increases in local cortical activity, but the amplitude, , increases. We observe a “knee” in the spectra at , implying the existence of a characteristic time scale . Below , we explore two-power-law forms of the PSD, and demonstrate that there are activity-related fluctuations in the amplitude of a power-law process lying beneath the rhythms. Finally, we illustrate through simulation how, small-scale, simplified neuronal models could lead to these power-law observations. This suggests a new paradigm of non-oscillatory “asynchronous,” scale-free, changes in cortical potentials, corresponding to changes in mean population-averaged firing rate, to complement the prevalent “synchronous” rhythm-based paradigm.