Critical point network-based organizational principle of cortical spatiotemporal dynamics

Abstract

Inspired by the field of turbulence and vector field topology in neural activities, this thesis introduces a novel and generalizable organizational principle of cortical spatiotemporal dynamics based on a global network of interacting critical points. Starting from the analysis of human fMRI signals, this thesis highlights the discovery of travelling cortical spiral waves (termed ‘brain spirals’) during both the resting and task states, emphasizing the mechanistic and functional relevance of a novel spiralbased organizational principle of large-scale brain activities. Next, based on human high-density electroencephalography (HdEEG) recordings, this thesis extends the spiral-based organizational principle from wakefulness to non-rapid-eye-movement (NREM) sleep, revealing that this spiralbased organizational principle is also a defining feature of human N2 sleep, which is associated with sleep-dependent-memory-consolidation and aging-related memory decline. Finally, this thesis further expands the spiral-based organizational principle to include other types of critical points (i.e., sinks, sources and saddles), two new recording modalities (Magnetoencephalography/MEG and Electrocorticography/ECoG), and intracranial recordings of non-human primates (marmoset). In two distinct datasets, a global network of interacting critical points can be consistently observed regardless of species, recording modalities and cognitive states. Acting like an organizational skeleton, this network of critical points collectively enables the task-dependent organizations of largescale brain activities, supporting the universal presence of a critical point network-based organizational principle of large-scale brain activities across species.