Time meets space – brain dynamics drive spatial topography

The brain exhibits both spatial and temporal hierarchy with their relationship remaining an open question. We address this issue by investigating the brain’s spatial hierarchy with complexity, i.e., Lempel-Zev Complexity (LZC) and temporal dynamics, i.e., median frequency (MF) in rest/task fMRI (including replication data). Our results are: (I) topographical differences in rest between higher-order networks (lower LZC and MF) and lower-order networks (higher LZC and MF); (II) task-specific increases and task-unspecific decreases in LZC and MF; (III) non-linear topographical relationship with low MF mediating higher LZC rest-task changes as confirmed in various simulations. Together, we demonstrate convergence of spatial (LZC) and temporal (MF) hierarchies in a non-linear topographical way along the lines of higher-order/slow frequency and lower-order/fast frequency networks.