How to never forget: some have such fine-tuned memories, they can relive individual moments

Highly Superior Autobiographical Memory can recall past episodes with rare clarity

At the Inserm lab, Pepper the robot helps research orientated to autobiographical memory. The robot is taught to access its memories and give them meaning, particularly with the elderly / Getty

A few weeks ago, I was reminiscing with friends about our schooldays. There was a lot of laughter – until someone mentioned a friend of ours who died in a car accident back then.

All of a sudden, the joy of sharing memories was gone. It was replaced instantly by a long silence as we remembered the loss of our friend and the sadness we experienced more than 25 years ago.

It had been years since I last thought about this friend. And the chances are, without seeing my friends that night, I might have gone years more without thinking about him.

But although I had forgotten many important details, such as the exact year it happened, I had not forgotten how I felt, who I was with and what I was doing when I found out about his death.

This is both sad and somewhat useful from a mental health point of view. The ability to forget about traumatic experiences – at least temporarily – is vital for people to move on with their lives and not get stuck in the past.

Some people do not have the freedom to forget at all. I am not speaking about those who work hard to be memory wizards, such as Suresh Kumar Sharma from India, the world record-holder of the largest number of pi digits memorised and recited (70,030 at the last count).

I am referring to the few people who have highly superior autobiographical memory (HSAM), a phenomenon first reported in 2006 by scientists from the University of California Irvine Center for the Neurobiology of Learning and Memory

Previously referred to as hyperthymesia, HSAM can be described as the ability of individuals to recall vividly and in great detail what happened in their lives on a given date.

There are about 100 people worldwide who have this extraordinary ability. But some see it as a curse because it prevents them from forgetting past traumas.

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Earlier this year Jason Brandt and Arnold Bakker from the Johns Hopkins School of Medicine published a study which used structural and functional magnetic resonance imaging (MRI) to explore the activity in the brain of a man exhibiting a clear case of HSAM.

His HSAM abilities were first identified from interviews about his life and his results at various advanced cognitive, personality and memory tests.

The scientists concluded his “ability to recall general factual information, historical facts and dates, sports statistics and popular culture, as well as personal life experiences, is exceptional, even though he performs in only the average range on tests of intellect and new learning ability”.

Thanks to neurotechnology, they identified neuroanatomical differences in his temporal lobe and hyper connectivity between his left hippocampus – a part of the brain playing a key role in memory – and other regions of the brain, compared with other people.

Simply put, it seems that a key component of his brain’s memory system communicates more with other parts of the brain compared to people who do not have HSAM.

There seem to be a growing interest in HSAM cases, as illustrated by Italian researchers who published a study last month in the Proceedings of the National Academy of Sciences of the United States, together with the scientist who first identified HSAM more than a decade ago.

This group also used functional MRI to compare the brain activity of eight HSAM individuals with 21 control test people, all of whom were required to retrieve autobiographical and non-autobiographical memories while their brains were scanned.

Unsurprisingly, HSAM individuals had better and faster recollection of past experiences which were autobiographical.

Similarly to what was found in the Johns Hopkins study, the connectivity between the hippocampus and other parts of the brain was enhanced.

Interestingly, the results also showed increased coupling with sensory cortices. The latter hints at HSAM individuals possibly relying more on their senses to recall autobiographical memories than control participants in the experiment.

Although not mentioned explicitly by researchers, some HSAM individuals reported reliving experiences in a sensory way as if they are still happening, rather than recalling events the way most people do.

As Japanese author Haruki Murakami wrote in his 2002 novel Kafka on the Shore, "memories warm you up from the inside. But they also tear you apart".

Clearly our ability to remember and to forget has a great impact on how we lead our lives.

Above all, memory is not just a way to remember the past but a system that allows us to design our future.

Professor Olivier Oullier is the president of Emotiv, a neuroscientist and a DJ