From KurzweilAI:
Gerald Burgess, a University of Leicester lecturer in clinical psychology, has described treating an individual who suffered a “Memento/Before I Go to Sleep“-style anterograde amnesia memory loss after a treatment at a dentist — “like nothing we have ever seen before.” Since the one-hour root-canal treatment, during which the a 38-year-old man from the UK was given a local anesthetic, the individual cannot remember anything beyond 90 minutes. He is fully aware of his identity and his personality did not change, says Burgess, but every day the man thinks it is the day of his dental appointment. He has to manage his life through an electronic diary and access to prompts. Burgess has now described the study, done a decade ago, in an open-access paper published in May in the journal Neurocase. He is also appealing for people who know of someone who might have suffered similar symptoms of memory loss, or medical or allied health professionals working with someone like this, to contact him to build up knowledge and evidence in this field of study.
Possible explanations
Burgess notes that “what we did know about from decades of research and hundreds of case studies, is that bilateral damage to the hippocampal and/or diencephalon structures causes profound amnesia … [but] we should perhaps not be so stuck in thinking that profound amnesia only occurs in the context of visible damage to the brain’s hippocampal and/or diencephalon structures. “Those structures appear just to be needed for the initial holding or retention of information before engrams then proceed slowly through several other neuro-electrical and neuro-chemical events, before finally permanent memories are stored, and that something can occur at some later point in this process to vanquish the memory trace permanently.
More here.