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.
Progress in AI is turning machine consciousness from a philosophical curiosity into a societal issue, prompting criticism of computational functionalism. Biological Naturalism (BN) claims biology, not computation, is crucial for consciousness. Two forms are distinguished: Type-A BN holds that biology intrinsically matters for consciousness without affording unique information processing capabilities, which dissociates consciousness from behavior and makes it untestable. Type-B BN holds that biology matters because it affords unique information processing capabilities; this form is testable and not incompatible with computational functionalism. Both face the same task of relating consciousness to information processing, with biology serving as a guide but not a solution.