Emergent effects of synaptic connectivity on cortical sleep slow wave amplitude, density and propagation in a large-scale thalamocortical network model of the human brain

Abstract

AbstractSlow-wave sleep (SWS), characterized by slow oscillation (SO, <1Hz) of alternating active and silent states in the thalamocortical network, is a primary brain state during Non-Rapid Eye Movement (NREM) sleep. However, the understanding of how global SO emerges from micro-scale neuron dynamics and network connectivity remains unclear. We developed a multi-scale, biophysically realistic human "whole-brain" thalamocortical network model capable of transitioning between the awake state and slow-wave sleep, and we investigated the role of connectivity in the spatio-temporal dynamics of sleep SO. SO remained robust in the face of substantial changes in connection weights, delays, sparsity, and range. However, extreme changes triggered distinct alterations in network behavior. Long synaptic delays led to the loss of downstates, while a reduction of over 50% in connection density decreased both SO frequency and amplitude. Even partial removal of local connections severely disrupted wave propagation. Lastly, reductions in long-range connection strength resulted in loss of global synchronization and led to the local propagation of slow waves. These results shed light on how the spatio-temporal properties of SO emerge from local and global cortical connectivity and provide a framework for further exploring mechanism and functions of SWS in health and diseases.