Hippocampus DBS in Treatment-resistant Schizophrenia

The first phase of the study will consist of DBS surgery. Participants will receive electrodes implantation in bilateral ventral hippocampus. Continuous stimulation will be applied to optimize and individualize the stimulus parameters. This period is anticipated between 3 and 6 months. The next phase will consist of the crossover study. Patients who respond to DBS will be randomly assigned to two groups, for a period of 3 months: on stimulation group and off stimulation group. Patients will then be crossed over to the other group for a further 3 months. Participants will receive PET-CT, clinical assessment and cognitive tests at the main study points to evaluate treatment efficacy and patient tolerance, and to reveal the underlying mechanism of the treatment effect of DBS.