Subanaesthetic doses of ketamine produce altered states of consciousness dominated by dissociative experiences such as disembodiment and ego transcendence, along with sensory disturbances. These subjective effects occur alongside a broad decrease in low-frequency brain electrical activity, with the largest reductions in alpha power (8–12 Hz) in parietal and occipital regions. Specific decreases in alpha power were identified in the precuneus and temporal-parietal junction, brain areas involved in multisensory integration, body representation, and consciousness. The findings suggest that modulation of these temporal-parietal loci may be a candidate mechanism for ketamine's psychoactive effects.
Selfhood depends on brain processes that allow a person to experience being a distinct, capable agent. It includes a hierarchy of components: core self (awareness of existence), embodied self (sentience), executive self (agency), and higher-order cognition. Consciousness and selfhood are related but not identical; understanding selfhood helps explain partial consciousness during anesthesia. Brain-imaging and EEG studies show that anesthetic drugs selectively impair self-related networks, especially the anterior insula and salience network, causing depersonalization at moderate doses while preserving disembodied self-awareness. Unlike natural sleep, where loss of agency and sentience tracks with decreasing self-awareness, anesthesia maintains posterior brain connectivity even at high concentrations, possibly marking a core self involved in reduced energy homeostasis.