A dynamic bifurcation mechanism explains cortex-wide neural correlates of conscious access.
Cell reports – March 25, 2025
Source: PubMed
Summary
Ignition, a critical process for conscious access, involves widespread activation across brain regions. A computer simulation using a mesoscale model of the macaque cortex revealed that a hierarchical gradient of N-methyl-D-aspartate (NMDA) and AMPA receptors is essential for this phenomenon. Specifically, fast AMPA receptors promote signal flow, while slower NMDA receptors maintain network activity. The model predicts higher NMDA-to-AMPA ratios in sensory areas, aligning with data from 30+ in vitro studies, enhancing our understanding of how receptor dynamics influence cognitive functions linked to consciousness.
Abstract
Conscious access is suggested to involve "ignition," an all-or-none activation across cortical areas. To elucidate this phenomenon, we carry out computer simulations of a detection task using a mesoscale connectome-based model for the multiregional macaque cortex. The model uncovers a dynamic bifurcation mechanism that gives rise to ignition in a network of associative regions. A hierarchical N-methyl-D-aspartate (NMDA)/α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor gradient plays a critical role: fast AMPA receptors drive feedforward signal propagation, while slow NMDA receptors in feedback pathways shape and sustain the ignited network. Intriguingly, the model suggests higher NMDA-to-AMPA receptor ratios in sensory areas compared to association areas, a prediction supported by in vitro autoradiography data. Furthermore, the model accounts for diverse behavioral and physiological phenomena linked to consciousness. This work sheds light on how receptor gradients along the cortical hierarchy enable distributed cognitive functions and provides a biologically constrained computational framework for investigating the neurophysiological basis of conscious access.