when something you have seen or heard becomes an actual memory trace in your brain you can say that
Confabulation In psychiatry, confabulation (verb: confabulate) is a disturbance of memory, defined as the production of fabricated, distorted, or misinterpreted memories about oneself or the world, without the conscious intention to deceive.[1] People who confabulate present incorrect memories ranging from "subtle alterations to bizarre fabrications",[2] and are generally very confident about their recollections, despite contradictory evidence.[3]