The brain may operate near a critical tipping point, a state thought necessary for consciousness and complex cognition. Using invasive ECoG recordings from a macaque transitioning between consciousness and unconsciousness under propofol and ketamine, the study found that propofol dramatically restricted the size and duration of neural avalanches and reduced the complexity of brain dynamics, while ketamine allowed more awake-like dynamics to persist. Despite these differences, all states showed some signs of persistent criticality when tested for exponent relations and universal shape-collapse, suggesting that maintenance of critical brain dynamics may be important for regulating conscious awareness.
The psychedelic DPT reversibly alters how information is processed in rat cortical tissue. Spontaneous neural firing became more random (higher entropy), and individual neurons stored information for shorter periods. Neural activity became less reversible, pushing the system away from equilibrium. Circuit structure shifted: overall information flow into each neuron decreased, but weak connections increased, blending integration and disintegration. Higher-order statistical synergy among groups of three neurons also dropped. These meso-scale effects offer a more detailed view of psychedelic action than whole-brain imaging provides.