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In the 1970s, Roger Brown and James Kulik, then psychologists at Harvard University in the United States, studied what a group of volunteers remembered of the Kennedy assassination. The subjects provided rich details of what they were doing when they learnt the news. More recently, many of us can remember exactly the moment we learnt of the 11th September attacks, or on a more joyful note, the results of the football World Cup final in 1998. These “flash memories” are like photographs that fix the most insignificant details of a special memory.
What if the phenomenon could be harnessed to improve learning? In 2016, the eminent memory specialist Richard Morris and his team at Edinburgh University trained mice daily to detect food buried in sand inside an enclosure, changing the location of the reward each time. Then the scientists conducted a test. First the trained mice had to find a reward buried in the enclosure. Then, when they were reintroduced one hour later, they would scratch at the sand where the food was. However, the next day they would dig everywhere randomly, as if the memory had disappeared. More surprisingly: if, just after finding the reward, the mice were installed in a new enclosure rich in colours and textures, when back in the first enclosure 24 hours later, they immediately went to the place where the food was buried, as if they had memorised its location. How can an ephemeral, ordinary memory suddenly become so persistent?
The type of memory studied here – the one associated to life’s events –, is processed in the hippocampus, a region of the brain that, if missing, would deprive us of the ability to form new memories and would imprison us in a time bubble just a few minutes long. Scientists have discovered another area of the brain, the locus coeruleus, responsible for the “flash memory” phenomenon. When it activates during an unexpected situation (like that of the mice), it remotely strengthens the activity of the neurons in the hippocampus, the ones corresponding to that unexpected event and the less important memories that precede and follow it by a few hours. The memories of events close in time are connected to each other in that they share the same biological soil. At each new experience, a set of neurons in the hippocampus is “allocated” by the brain to form a new memory. This closely studied process is continuous. If a few minutes separate two experiences lived in the same environment, only a few neurons will differ in the two corresponding sets of neurons. However, the more time passes, the smaller the overlap. So, when an important memory forms, it is associated with the activation of a set of neurons, most of which are also activated for the preceding and subsequent banal memories.
Even though we did not need these discoveries to understand that the learning context is decisive in dissociating the knowledge of various subjects (for example, physics and French are taught in different rooms), it would be useful to combine the learning of complex notions with strong, surprising experiences. In the classes I give at university, I often start with a video extract of a cultural work, closely or loosely related to the subject in hand. The impact on attention is instant, and I hope that these students will remember my lessons for a long time. Putting it into practice in school is often confronted with the reality in the field, but given the importance of the challenge, it would be a pity not to explore this avenue.
Adrien Peyrache heads at McGill University in Canada a research laboratory devoted to studying the neuronal processes involved in spatial navigation and memory.