Ketamine administration in healthy participants caused an altered state of consciousness and changes in systemic physiology, including increased pulse rate and electrodermal activity. The drug led to a brain-wide reduction in the fractional amplitude of low frequency fluctuations and decreased global brain connectivity in the prefrontal region. Preliminary evidence suggests that a combination of neural and physiological metrics may predict subjective mystical experiences and reductions in depressive symptoms. The study demonstrates the successful use of fNIRS neuroimaging to measure physiological effects of ketamine in a clinical setting, representing a step toward larger clinical fNIRS studies of psychedelics.
Ketamine reduced brain-wide low-frequency fluctuations and decreased prefrontal global brain connectivity in healthy adults, while also increasing pulse rate and electrodermal activity. A combination of neural and physiological metrics may predict subjective mystical experiences and reductions in depressive symptoms. The study used time-domain functional near-infrared spectroscopy to measure acute brain dynamics after intramuscular ketamine (0.75 mg/kg) or placebo in 15 participants within a clinical setting, demonstrating the feasibility of this neuroimaging method for larger clinical studies on psychedelics.