Engramatic dissociation was a theory that suggested that if one disciplined one's mind sufficiently, one could hold one set of beliefs and simultaneously act in a manner contrary to those beliefs, by compartmentalizing their thoughts and actions in different layers of memory.
In 2374, Luther Sloan asked Julian Bashir if he was familiar with the term, after which the doctor confessed having a vague knowledge of what it entailed. He went on to surmise that Bashir's mind was capable of such, and as such, the Dominion successfully turned him and made him suppress his memories of it. He asked Bashir to try and remember what he'd supposedly suppressed. Bashir refused, saying he was loyal and possessed no such memories. (DS9: "Inquisition")