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The people who are lost in time

What is it like to lose your memory after brain injury, drug abuse – or energetic sex? Christian Jarrett reports on the strange causes and consequences of amnesia.

One morning in 2008, Naomi Jacobs, then 32, woke up with no recollection of her previous 17 years. It’s as if the memories of drug abuse, bankruptcy and homelessness had been wiped from her mind. In fact, she says her last memory was of going to sleep as a teenager in the bunk bed she used to share with her sister, and of thinking about her upcoming French exam.

Eight weeks later her memories returned, but before they did, Jacobs says she had to negotiate the 21st Century world as her 15-year-old self. This meant learning to use “new” technologies like smart phones, but most challenging of all, it meant coming to terms with the fact that she had a 10-year-old son. Jacobs’ incredible story is told in her forthcoming book Forgotten Girl and you can hear her talk in this BBC interview.

Split minds

From a medical perspective, Jacobs’ memory loss is considered to be a case of dissociative amnesia. This means there is no physiological explanation for why she temporarily lost 17 years’ worth of memories. Instead, the forgetting is psychological (or “psychogenic”), possibly brought on by recent or historical stress and trauma. Consistent with this, Jacobs says that not only had she lost her business and abused drugs in those forgotten years, she was raped at age six, and a boyfriend tried to strangle her when she was 20.

Dissociative amnesia is a controversial diagnosis. Some scholars, such as Harvard psychiatrist Harrison Pope, dispute that it really exists. They point out that there are no historical references to the condition prior to 1800. Other sceptics propose that the dissociative disorders (including dissociative identity disorder, previously known as multiple identity disorder) are not so much an automatic coping strategy triggered by trauma, but rather more a consequence of the patients’ expectations for how they ought to behave, prompted in part by therapists’ suggestions and fictional portrayals of illness.

Complementing this picture, people diagnosed with dissociative disorders typically also have diagnoses of personality disorders and emotional instabilities. They also tend to score highly in suggestibility and fantasy proneness. At the time of her memory loss, Jacobs was studying psychology, which may have exposed her to ideas about trauma and memory functioning. In an interview with the Sunday Times, she says she has “great reverence” for the mind. “I know that my way of dealing with trauma is for my mind to split,” she adds.

The power of a patient’s expectations certainly seems to lie behind another striking case. After a car crash, the patient reported that her memories were wiped clean each night. This is a symptom that makes no physiological sense but it’s precisely what happens to Drew Barrymore’s character after a crash in the film 50 First Dates, released in 2004. Crucially, when the researchers tricked the patient, testing her on material that she thought was from the same day, but was really from the day before, her performance was unimpaired. The researchers don’t think the woman – a Drew Barrymore fan – was malingering (although other experts are more sceptical), but they do think the manifestation of her psychogenic amnesia was likely influenced by the portrayal of memory loss in the film.

These cases of psychogenic or dissociative amnesia are relatively rare. More common is organic amnesia, of the kind caused by damage to the brain or neurological illness, such as stroke. When these kinds of patients present at the clinic, their problem isn’t usually that they’ve forgotten episodes from their past, or that they’ve lost their identity; it’s that they are unable to form new memories.

Stuck in the present

So-called “anterograde amnesia” of this kind is usually caused by damage to the hippocampus – a structure housed in each of the temporal lobes (near the ears) that plays an important part in memory. Probably the most studied amnesiac is the late Henry Molaison. A surgeon removed large parts of his hippocampi (and both his amygdalae) as part of a radical treatment for his epilepsy, conducted in 1953. The procedure stopped the seizures but left him permanently stuck in the present.

Although he knew his identity and could remember some past episodes, most of his new memories never lasted more than a few seconds. Brenda Milner, who studied Molaison for years, has described how he greeted her as a stranger each day. After eating a meal, he would sit down to eat another half an hour later – and he couldn’t remember his plans from one moment to the next. Researchers also discovered that Molaison had unusually high pain tolerance (they tested this by subjecting his arm to heat from a hair-dryer-like contraption). Our experience of pain is related in part to our memory of past painful experiences, so it's possible that Molaison's pain tolerance was affected by the removal of his amygdalae, a brain structure involved in remembering previous painful episodes.

Other forms of organic amnesia are brought about by concussion, and heavy drug and alcohol use. Although many alcohol-induced blackouts are triggered by a single episode, long-term alcoholism can also cause a condition known as Korsakoff’s syndrome, that disrupts both memories from the past and the formation of new memories from the present. The patients often fill the gaps in their past with confabulated stories – these are totally fictional, but they seem to believe them to be true.

More rare is transient global amnesia, which is when memory loss is caused by a temporary drop in blood flow to parts of the brain involved in memory function. The causes of this kind of disrupted blood flow can vary and, according to a report published in 2011, include energetic intercourse. In this case, a 54-year-old woman claimed that she had lost all her memories from the 24-hour-period prior to climaxing: that’s what you call mind-blowing sex.

In a sense, we are all amnesiacs: it is rare for most people to recall the first three or four years of their lives. It’s not that we are incapable of forming long-term memories at this early age (three-year-olds, for example, can happily reminisce about earlier memories), but somehow these recollections are lost as we grow into later childhood and adolescence. A recent study suggested that the infantile amnesia process kicks in at around the age of seven and may be a side-effect of the maturation of memory functioning. Curiously, though, there’s evidence that infantile amnesia is to some extent influenced by culture. For instance, first memories are earlier among the New Zealand Maori than among New Zealand citizens of European descent and Asian people, perhaps because Maori cultures place so much emphasis on story-telling about the past.

That smudge in our early memories is nothing compared to the experiences of people with more serious forms of amnesia – for many, it feels like a gaping chasm in their lives. Our recollections are the very core of our being, around which we build our identity, our relationships, our hopes and our dreams. When we lose our memories, we really lose ourselves.

Christian Jarrett