Transient global amnesia disrupts short-term memory, but leaves the person's consciousness more-or-less intact and it wears of over time.
The funny thing is that people remember only what happened a minute or so in the past. As a result they often have the exact same responses to their surroundings. They get caught in these loops where they will have the exact same minute or two long conversation over and over for hours. It is as if the choices they make are more influenced by external stimuli than some internal free will.