RT Journal Article SR Electronic T1 The timescale and magnitude of aperiodic activity decreases with cortical depth in humans, macaques and mice JF bioRxiv FD Cold Spring Harbor Laboratory SP 2021.07.28.454235 DO 10.1101/2021.07.28.454235 A1 Halgren, Mila A1 Kang, Raphi A1 Voytek, Bradley A1 Ulbert, Istvan A1 Fabo, Daniel A1 Eross, Lorand A1 Wittner, Lucia A1 Madsen, Joseph A1 Doyle, Werner K A1 Devinsky, Orrin A1 Halgren, Eric A1 Harnett, Mark A1 Cash, Sydney S. YR 2021 UL http://biorxiv.org/content/early/2021/07/29/2021.07.28.454235.abstract AB Cortical dynamics obey a 1/f power law, exhibiting an exponential decay of spectral power with increasing frequency. The slope and offset of this 1/f decay reflect the timescale and magnitude of aperiodic neural activity, respectively. These properties are tightly linked to cellular and circuit mechanisms (e.g. excitation:inhibition balance, firing rates) as well as cognitive processes (perception, memory, state). However, the physiology underlying the 1/f power law in cortical dynamics is not well understood. Here, we compared laminar recordings from human, macaque and mouse cortex to evaluate how 1/f aperiodic dynamics vary across cortical layers and species. We report that 1/f slope is steepest in superficial layers and flattest in deep layers in each species. Additionally, the magnitude of this 1/f decay is greatest in superficial cortex and decreases with depth. Both of these findings can be accounted for by a simple model in which transmembrane currents have longer time constants and greater densities in superficial cortical layers. Together, our results provide novel mechanistic insight into aperiodic dynamics in cortex and suggest that the timescale and magnitude of aperiodic cortical currents decrease with cortical depth.Competing Interest StatementThe authors have declared no competing interest.