In mice, the serotonergic psychedelic DOI, but not ketamine, enhanced neural plasticity and metaplasticity in the hippocampus 24 hours after a single dose. Brain slices from DOI-treated animals showed stronger synaptic responses and short-term potentiation compared to saline-treated controls, with evidence that these effects involve a presynaptic mechanism. Ketamine did not produce similar changes. These findings suggest that the therapeutic benefits of serotonergic psychedelics may be supported by a window of heightened neural plasticity, whereas ketamine's effects may rely on different mechanisms.
Many EEG-based measures previously thought to indicate unconsciousness actually track sensory connectedness—awareness of the environment—rather than consciousness itself. Analyzing data from the UNderstanding Consciousness Connectedness and Intra-Operative Unresponsiveness Study, researchers tested 10 resting-state EEG markers derived from unresponsive subjects during dexmedetomidine and propofol sedation and natural sleep. While several markers correlated with reported subjective experience (consciousness), none were specific to consciousness alone; each was also linked to connectedness. Loss of normalized-symbolic transfer entropy (front to back) was associated with connectedness across all conditions, and the shift from disconnected consciousness to unconsciousness involved significant decreases in permutation entropy and spectral exponent. The findings caution against equating unresponsiveness with unconsciousness.