High-order brain interactions in ketamine during rest and task: A double-blinded cross-over design using portable EEG.

Ketamine increases redundancy in brain dynamics, particularly in the alpha frequency band, and this effect is more pronounced during resting state and associated with dissociative experiences. In a double-blinded cross-over design with 30 male adults, racemic ketamine was compared to saline infusion. Higher-order interactions (HOI) computed from EEG data showed that ketamine boosted redundancy, especially for predictable stimuli in an auditory oddball task. These findings suggest that ketamine-induced shifts toward dissociation correlate with increased redundancy in neural signal interactions, highlighting the potential of complexity measures with portable EEG for monitoring pharmacological changes in consciousness.

Study at a glance

Abstract

In a double-blinded cross-over design, 30 adults (mean age = 25.57, SD = 3.74; all male) were administered racemic ketamine and compared against saline infusion as a control. Both task-driven (auditory oddball paradigm) and resting-state EEG were recorded. HOI were computed using advanced multivariate information theory tools, allowing us to quantify nonlinear statistical dependencies between all possible electrode combinations. Results: Ketamine increased redundancy in brain dynamics, most significantly in the alpha frequency band. Redundancy was more evident during the resting state, associated with a shift in conscious states towards more dissociative tendencies. Furthermore, in the task-driven context (auditory oddball), the impact of ketamine on redundancy was more significant for predictable (standard stimuli) compared to deviant ones. Finally, associations were observed between ketamine's HOI and experiences of derealization. Conclusions: Ketamine appears to increase redundancy and genuine HOI across metrics, suggesting these effects correlate with consciousness alterations towards dissociation. HOI represents an innovative method to combine all signal spatial interactions obtained from low-density dry EEG in drug interventions, as it is the only approach that exploits all possible combinations from different electrodes. This research emphasizes the potential of complexity measures coupled with portable EEG devices in monitoring shifts in consciousness, especially when paired with low-density configurations, paving the way for better understanding and monitoring of pharmacological-induced changes.