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.
Psilocybin at therapeutically relevant doses (0.3 or 1 mg/kg) in rats unmasked 100 Hz high frequency oscillations in the infralimbic cortex that persisted for about an hour, accompanied by decreased pyramidal cell firing rates and reduced signal complexity. These acute effects were more pronounced during rest than during a sustained attention task. Over the following days, gradually emerging increases in beta and low-gamma (20-60 Hz) power appeared specifically in the infralimbic cortex, suggesting network plasticity on multi-day timescales. The findings implicate infralimbic network oscillations as potential biomarkers of psychedelic action not readily detectable 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.