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.
Consciousness is thought to fluctuate with the integration of brain areas across the wake-sleep cycle, but recent evidence suggests consciousness may not be uniformly present or absent within a given brain state, as conscious reports can occur during Non-REM sleep. This study tested whether functional connectivity between neurons varies within brain states in a way that reflects changing levels of consciousness. In rats, directed functional connectivity between neurons was examined across the wake-sleep cycle at a scale of a few seconds. The analysis aimed to determine whether Non-REM sleep contains epochs with inter-areal integration comparable to wakefulness and REM sleep, and vice versa. The findings could reveal circuit-level connectivity patterns consistent with alternating levels of consciousness both between and within brain states.