Dynamic reconfiguration of frequency-specific cortical coactivation patterns during psychedelic and anesthetized states induced by ketamine

Spontaneous brain activity explores a repertoire of recurring spatial patterns, and the richness of this repertoire may reflect the capacity for consciousness. Ketamine, which has both psychedelic and anesthetic properties depending on dose, was used to examine brain dynamics across a continuum of consciousness. Analyzing EEG data from source-localized cortical activity, researchers identified frequency-specific spatial coactivation patterns. Ketamine anesthesia shifted brain states toward those with low spatial variability. Subanesthetic ketamine was associated with a richer repertoire of brain states, while anesthetic ketamine initially reduced repertoire richness, which then evolved to a level comparable to normal wakefulness before recovery of consciousness. These findings describe ketamine's modulation of cortical dynamics across spatial, temporal, and spectral dimensions.

Study at a glance

Abstract

Recent neuroimaging studies have demonstrated that spontaneous brain activity exhibits rich spatiotemporal structure that can be characterized as the exploration of a repertoire of spatially distributed patterns that recur over time. The repertoire of brain states may reflect the capacity for consciousness, since general anesthetics suppress and psychedelic drugs enhance such dynamics. However, the modulation of brain activity repertoire across varying states of consciousness has not yet been studied in a systematic and unified framework. As a unique drug that has both psychedelic and anesthetic properties depending on the dose, ketamine offers an opportunity to examine brain reconfiguration dynamics along a continuum of consciousness. Here we investigated the dynamic organization of cortical activity during wakefulness and during altered states of consciousness induced by different doses of ketamine. Through k-means clustering analysis of the envelope data of source-localized electroencephalographic (EEG) signals, we identified a set of recurring states that represent frequency-specific spatial coactivation patterns. We quantified the effect of ketamine on individual brain states in terms of fractional occupancy and transition probabilities and found that ketamine anesthesia tends to shift the configuration toward brain states with low spatial variability. Furthermore, by assessing the temporal dynamics of the occurrence and transitions of brain states, we showed that subanesthetic ketamine is associated with a richer repertoire, while anesthetic ketamine induces dynamic changes in brain state organization, with the repertoire richness evolving from a reduced level to one comparable to that of normal wakefulness before recovery of consciousness. These results provide a novel description of ketamine's modulation of the dynamic configuration of cortical activity and advance understanding of the neurophysiological mechanism of ketamine in terms of the spatial, temporal, and spectral structures of underlying whole-brain dynamics.