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.
After a therapeutically relevant dose of psilocybin, high-frequency oscillations at 100 Hz appear in the infralimbic cortex of rats, lasting about an hour, while overall neuron firing rates and spike-train complexity decrease. These acute effects are stronger when the animal is at rest than during a sustained attention task. Over the following days, power in beta and low-gamma frequencies (20–60 Hz) gradually increases in the infralimbic cortex. The findings point to infralimbic network oscillations as potential markers of psychedelic-induced plasticity that unfold over multiple days, revealing details not easily seen in human brain imaging.
A correction notice addresses an error in a previously published article: the author's name Robin Carhart-Harris was incorrectly written as Robin Carhartt-Harris. The original article has been corrected.