ZEIT online has an interesting article about ddéjà-vu - a rare syndrome. Some psychiatrists believe that déjà-vu episodes are the result of a faulty memory that brings up a similar episode. Others believe that there is nothing at all – just electric loops of a petite mals that can also be triggered by electric stimulation of the gyrus parahippocampus. ZEIT online also cites a study of Alan Brown that adds evidence for some kind of implantable memory.
I have frequently déjà-vus when reading the scientific literature (sometimes I even believe in groundhog days). One of my teachers in Marburg always said that “study of the scientific literature prevents from new discoveries”. Yea, yea.