Mr. B loves Johnny Cash, except when he doesn’t. Mr. X has watched his doctors morph into Italian chefs right before his eyes. The link between the two? Both Mr. B and Mr. X received deep brain stimulation (DBS), a procedure involving an implant that sends electric impulses to specific targets in the brain to alter neural activity. While brain implants aim to treat neural dysfunction, cases like these demonstrate that they may influence an individual’s perception of the world and behavior in undesired ways.