Two anesthetics with different molecular actions, ketamine and dexmedetomidine, both increase phase locking of neural oscillations in the prefrontal cortex of nonhuman primates during loss of responsiveness. Within a hemisphere, neighboring prefrontal subregions become less phase-aligned, possibly due to large traveling waves. However, homologous areas across hemispheres become more aligned in phase. These distinct patterns of cortical phase alignment, markedly different from waking states, may represent a common mechanism by which diverse anesthetics produce loss of responsiveness.
Convergent neurons—those that receive input from multiple sources but do not integrate that information—more readily exhibit properties of consciousness than integrative neurons, contrary to the predictions of integrated information theory. In nonhuman primates under propofol anesthesia, convergent neurons showed greater neural complexity and noise correlation, and were more impacted during loss of consciousness. Neural ignition, the coactivation of primary somatosensory and ventral premotor cortex on the same trial, was more frequent in conscious states, supporting the global neuronal workspace theory. The findings directly contrast two major theories of consciousness within a single dataset.