Study procedures
Resting-state (rs)fMRI imaging was carried out in the context of a double-blind randomized placebo-controlled crossover study. Participants were randomized to receive either a single intravenous infusion of ketamine hydrochloride (0.5 mg/kg over 40 min) or placebo (0.9% saline solution) during the first session, and the converse treatment during the second session two weeks later. rsfMRI scans were obtained 2 days after each infusion. MADRS, Snaith–Hamilton Pleasure Scale (SHAPS [The primary objective was to compare the seed-to-whole brain rsFC changes of sgACC, pgACC, and dACC with ketamine 