Harvard Gazette Q+A with Fangyun Tian who was the first author of a recent MGH study tracing the effects of ketamine, a fast-acting antidepressant with potential for abuse due to its dissociative effects, to three regions of the human brain. The prefrontal cortex and hippocampus are believed to have a role in the drug’s effectiveness as an antidepressant, while the posteromedial cortex, in the back portion of the brain, is a likely site for dissociative effects.