Conscious access involves 'ignition,' an all-or-none activation across cortical areas. Computer simulations of a detection task using a mesoscale connectome-based model of the macaque cortex reveal a dynamic bifurcation mechanism that produces ignition in a network of associative regions. A hierarchical NMDA/AMPA receptor gradient is critical: fast AMPA receptors drive feedforward signal propagation, while slow NMDA receptors in feedback pathways shape and sustain the ignited network. The model suggests higher NMDA-to-AMPA receptor ratios in sensory areas compared to association areas, a prediction supported by in vitro autoradiography data. The model accounts for diverse behavioral and physiological phenomena linked to consciousness.
Conscious perception of a word's meaning can occur even when its visual features are inaccessible. In an experiment, participants viewed briefly flashed, visually masked words. When a semantically related spoken word followed, they could better detect and identify the previous word but could not report its letter casing or screen position. This suggests that a semantic representation can reach awareness via retro-cueing after sensory details are masked, supporting theories that conscious access relies on a secondary broadcasting process largely independent of early sensory buildup.