Ketamine and Neurofeedback-Training: Effects on Neuroplasticity in Cocaine Addiction

The goal of this clinical trial is to learn about the effects of the combination of ketamine and realtime functional magnetic resonance imaging (fMRI) neurofeedback training in individuals with cocaine use disorder. The main questions the investigators aim to answer are:

* Can the investigators observe a positive, significant effect on percentage of cocaine use days of both interventions combined as well as stand alone interventions? * Is there a significant transfer effect of the neurofeedback training? * Is there a significant, ketamine-dependent change in glutamate levels in the nucleus accumbens?

Participants will be given ketamine and a realtime fMRI neurofeedback training. Both interventions are placebo-controlled. The investigators will compare the four intervention groups to investigate the effects of the stand-alone effects of the intervention and the combination of it.