Ketamine increases redundancy in brain dynamics—copies of the same information retrievable from three or more electrodes—most notably in the alpha frequency band, as measured by portable low-density EEG. In a double-blind crossover trial with 30 male adults, racemic ketamine compared to saline infusion produced greater redundancy during resting state, linked to dissociative shifts in consciousness. During an auditory oddball task, the effect was stronger for predictable standard stimuli than for deviant ones. Associations between ketamine's high-order interactions and experiences of derealization were observed, suggesting these measures capture pharmacological alterations in consciousness.
Ketamine produces short-lived increases in reward responsiveness in rats under nonstressful conditions, but under ongoing chronic stress it rescues blunted reward responsiveness for nearly one week. These findings highlight the role of environmental context in ketamine's effects on reward processing and suggest its antianhedonic action may contribute to its antidepressant efficacy.
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.