Suppressed neural complexity during ketamine- and propofol-induced unconsciousness

Topological Analysis of Differential Effects of Ketamine and Propofol Anesthesia on Brain Dynamics

“…One possible future direction would be to relate changes in the structure of embedded point clouds to more standard measures of multi-region coordination, such as functional connectivity. In the temporal domain, propofol has a clear effect of reducing the number of unique temporal states visited, which is consistent with previously reported results [68,54,63,61]. In addition, there is an apparent emergence of powerful attractor states that the brain repeatedly visits, over and over again, in contrast to both normal waking consciousness and the ketamine state.…”

“…Post-hoc analysis found that there was a significant reduction in the number of nodes between the Propofol condition (456.25 ± 57.1) and both the Awake (U = 19, p = 0.00018) and Ketamine (U = 17, p = 0.00014) conditions, but not between Awake (563.0 ± 68.0) and Ketamine (615.875 ± 110.5). This finding is consistent with previous findings that Ketamine, unlike Propofol, maintains or increases the algorithmic complexity of brain activity [55,63].…”

“…Overall we found that ketamine produced dynamics similar to normal waking consciousness while propofol did not, and the significance of these findings is discussed. different drugs with a specific focus on how different dynamics might relate to conscious awareness [55,63]. In this paper, we take such a comparative approach to explore the differences between the effects of propofol and ketamine on multi-scale brain dynamics with an eye specifically to how these dynamics might explain the differences in consciousness induced by both drugs.…”

“…In contrast, ketamine acts primarily as an antagonist of glutamaterigic NMDA receptors [29,66], causing widespread, light central nervous system stimulation and a state typically referred to as "dissociative anesthesia" [16,33]. Unlike propofol, which simply ablates consciousness, an otherwise unresponsive patient anesthetized with ketamine often continues to have complex, conscious experiences, including hallucinations, out-ofbody experiences, and dream-like, immersive experiences [66].It has been hypothesized that the differences between ketamine and propofol anesthesia are the result of changes to the global brain dynamics induced by each drug [63]. Experimental evidence suggests propofol inhibits the ability of the brain to maintain high levels of dynamical complexity, resulting in a low-entropy state insufficient for supporting conscious awareness [54,52].…”

Differential effect of anesthesia on visual cortex neurons with diverse population coupling

“…Considering the fact that soloists respond to sensory stimuli in a selective and precise manner [4,6], one could surmise that the absence of the actively firing soloists in anesthesia could be responsible for the disruption of conscious sensory information processing. This proposition is consistent with anesthetic-related changes in large-scale brain activity such as electroencephalogram, which exhibits slow oscillation, low-frequency synchronization (0.1-5 Hz), or suppressed signal complexity as typical signatures of anesthetic-induced unconsciousness [14][15][16].…”