However, a congenital (inherited birth defect) or developmental form of the disorder does exist, with a prevalence rate of 2.5%. That is quite a high rate. What this defect shows is that our picture of the world is built up by various brain systems, and we do not notice how this is done. It seems seamless and automatic. Actually, there are many brain mechanisms which normally work together, tying the visual scene to memory so that we recall vital information. It is difficult to think of anything more vital than remembering who we know, and what their relationship is to us. 