What did you do on March 13th, 1985? People with hyperthymesia (which has been characterized only recently, and of which just a handful of cases have so far been reported) would likely provide a vivid account of what happened on that day. And if this particular date has personal significance for you – if, for example, it was your wedding day, or the birth date of one of your children – then you will probably remember it quite well. But for most of us, the answer to this question is likely to be “I don’t know”.

In the journal Cortex, researchers describe the case of a patient with severe memory loss who has a tendency to invent detailed and perfectly plausible false memories (confabulations) in response to questions to which most people would answer “I don’t know”, such as the one above. They have named this unusual condition confabulatory hypermnesia, and believe that theirs is the first study to document it. 

The patient, a 68-year-old patient known as LM, had a history of heavy drinking which lasted more than 30 years and stopped just 3 months before the study was carried out. He was referred to the memory clinic at the Charles Foix Hospital in Ivry-sur-Seine for a neuropsychological evaluation after he began to experience memory loss and disorientation in time and space. A brain scan showed mild degeneration throughout the cerebral cortex and he was diagnosed with Korsakoff’s Syndrome, a neurodegenerative condition which occurs as a result of vitamin B₁ deficiency and is associated with long-term, chronic alcoholism.

Gianfranco Dalla Barba and Caroline Decaix asked LM a series of questions designed to evaluate the extent of his confabulations. The test contained 165 questions which required the retrieval of various kinds of information in each of 15 domains, including personal semantic memory (his age, date of birth, current address and marital status), episodic memory (autobiographical events), contemporary and historical semantic memory (knowledge of facts, news events and famous people) and episodic and semantic plans (or knowledge of events, both personal and otherwise, which are likely to take place in the next 10 years). The answers he provided were compared to to those of a healthy control participant and to information provided by his family and friends. LM was found to exhibit an unusual tendency to provide completely confabulated answers to questions in all of the domains tested.

For example, when asked about his brother’s job, he told the researchers that “Remy is an artist who works in variety shows”, confusing his brother with his son, who actually does work as an artist in variety shows; when asked “What month is it?”, he answered “The end of December”, when it was in fact April; to the question “What happened in May 1968?”, he responded with “It was the beginning of of the workmen’s revolution; the government opposed Africa”; when probed about what he thought would be the most important advance in space exploration in the next 10 years, he he replied “We will land on the Moon and…see if it is habitable”; and when asked to tell the researchers what he would be doing that evening, he presponded with “I’ll have dinner with my wife and then watch the television news”, despite the fact that he was hospitalized at the time, and that there was no television on his ward.

Most strikingly, LM confabulated plausible answers to questions about both his personal life and public events, which would normally elicit from most people an answer of “I don’t know”. When the researchers asked him “Who won the Palme d’Or at the Cannes Film Festival in 1980?” he replied “Fernandel”; when asked what he had for dinner on Tuesday two weeks ago, he answered “Steak with french fries”; and when asked “Do you remember what you did on March 13th, 1985?” he replied “We spent the day at the Senart Forest.”

LM thus has a “pure” amnesic syndrome, in that his impairment is not associated with other cognitive deficits which might interfere with memory function. He scored normally on short-term memory tests, and the evaluation revealed mild, diffuse neurodegeneration, rather than damage in a specific part of the brain. False memories are not uncommon in patients with Korsakoff’s syndrome – indeed the condition is also referred to as amnesic-confabulatory syndrome. However, the confabulations of such patients are sometimes extraordinary, bizarre and verging on being delusional. LM’s confabulations, on the other hand, were always plausible, and therefore quite unlike those reported in other Korsakoff’s patients.

Some researchers have argued that confabulation occurs as a result of errors in source monitoring and reality monitoring. The former is a process by which the reliability of information is evaluated; the latter refers to the ability to distinguish between information generated from the perception of real events and information conjured up by the imagination. But neither of these explanations can account for LM’s confabulations, as he did not mistake real events for imagined ones. He had often visited Senart Forest with his family, and steak and French fries is a very common meal in France, and therefore one which he is likely to have eaten many times in the past.

So how might LM’s amnesic syndrome arise? The authors explain it within the framework of the memory, consciousness and temporality theory. According to this theory, consciousness always relates to “something”, such as an object or event, and does not exist as a unitary dimension, but rather as a distinct set of “modes” for addressing the “thing” of which one is conscious of at any given moment. These modes include knowing consciousness and temporal consciousness, which describe, respectively, knowing the object of consciousness and placing it somewhere on the timeline of past, present and future.

For example, a pen is a pen and a meal is a meal, and each can be lumped together with others into the same category. But at a given moment, one  might be conscious of the pen sitting on a table, or of the meal that has just been eaten. Thus, every object or event which enters consciousness has both a multiplicity and a uniqueness. The authors suggest that LM may be unable to distinguish between these two properties. His temporal consciousness is  present, but working abnormally. It has become “expanded”, so that while he can retrieve information about personal events and habits, the particulars of a specific object of consciousness are applied to all the objects within that category, and they become confused with one another.

Related:

• Amnesia in the movies
• Anatomy of a false memory
• Igniting the flame of consciousness
• Doctored photos create false memories
  
  
• Reconstructive memory: Confabulating the past, simulating the future

Dalla Barba, G., & Decaix, C. (2009). “Do you remember what you did on March 13, 1985?” A case study of confabulatory hypermnesia. Cortex 45: 566-574. DOI: 10.1016/j.cortex.2008.03.009.