Do you remember what you did on March 13, 1985?
If somebody asks you "Do you remember what you did on March 13, 1985?" you are very likely to answer "I don't know", even if your memory is excellent.
In a study conducted by Dalla Barba and Decaix from the Institut National de la Santé et de la Recherche Médicale and the Department of Neurology of the Hôpital Saint Antoine in Paris and published by Elsevier in the May 2009 issue of Cortex, researchers found that a patient with severe amnesia reported detailed false memories in answering this type of question. People with normal memories are unable to answer this type of question because it is beyond their memory capacity. This is the first reported case of a pathological condition that the authors of the article named 'Confabulatory Hyperamnesia'.
Patient LM, described in this study, is a 68-year-old man, who, following more than 30 years of heavy drinking, developed Korsakoff's syndrome, a condition characterized by severe amnesia and confabulation, the unintentional production of false memories by amnesic patients who are unaware of their memory deficits. Patients who confabulate produce more or less plausible false memories answering questions like "What did you do yesterday?" or "How did you spend your last vacation?", but, just like people with normal memory, they answer "I don't know" to questions like "Do you remember what you did on March 13, 1985".
What makes LM different from other confabulators is his unusual tendency to consistently provide a confabulatory answer to this type of questions. He would say, for example, that on March 13, 1985 he spent the day at the Senart Forest (a place where he used to go often with his family) or that he could remember that on the first day of summer in 1979 he was wearing shorts and a T-shirt.
LM's confabulatory hyperamnesia could not be traced back to any specific pattern of brain damage and the MRI brain scan was unremarkable. The authors conclude that LM shows an expanded consciousness of his past, a consciousness which has surpassed the limits of time and details.
More information: The article is "Do you remember what you did on March 13, 1985?" A case study of confabulatory hyperamnesia" by Gianfranco Dalla Barba and Caroline Dacaix and appears in Cortex, Volume 45, Issue 5 (May 2009), published by Elsevier. www.elsevier.com/locate/cortex