The brain is made up of 100 billion nerve cells, neurons, which constitute a wired network in which memory, living matter, is found and will accompany each individual from his first learning to the advanced stages of old age. Guarantor of our individual autonomy and our collective ties, it influences our behavior and intervenes in our performance. It is increasingly studied by the various sciences but still conceals many mysteries.

Memory materializes in different ways: through neural networks which are widely distributed in the brain and whose connections and synchronization will make it possible to represent traces corresponding to memories or general knowledge. “These biochemical and electrical exchanges between these different cells will form this knowledge network“, explains Professor Francis Eustache, neuropsychologist. What will complicate the mechanism of memory is that there are different levels of understanding memory storage : a cellular and neurobiological level and more integrated levels which will focus on the major brain regions involved in theinformation, storage, retrieval of knowledge, memories, knowledge. “Memory is very complex, it is based both on biochemistry, but also on social and cognitive. Memory is remembering what we did last Saturday night, but it’s also knowing how to drive a car.“, he underlines.
Memory will refer, through its complex functioning, to completely different regions of the brain.

What part of the brain stores memories of the past?

Memories of the past are stored in a very important region of the brain: the seahorses. These 8-10 cm long brain structures are internal surface of the temporal lobes, on the sides of the brain at the level of the temples. “These regions are very important and could be compared to hubs: not everything is stored here but they function as indexes which are linked to different regions such as those of the cortex which surrounds the brain.“, he illustrates. The seahorses will make it possible to synchronize, coordinate the activity from different regions that will help recover memories and information from the past. The nuance is when we speak of “memories”, memories of the past, that is to say the events that I remember : “For example, when I was 15, I was in Brittany with my grandparents and the boat capsized and tourists hoisted me into their boat. This corresponds to a memory located in time and space, episodic memory, which is stored in seahorses“. On the other hand, if it is a matter of knowledge, something that I have learned and which has become general knowledge, the cerebral structures involved are different: “For example, when I was young, I always went on vacation to Brittany. It does not refer to a particular memory. I know a lot about this province because I used to go there quite often. At this moment, these memories that amalgamate with each other become relatively independent of the hippocampuss. We will solicit the semantic memory and therefore the regions of the neocortex and in particular the temporal poles“, he specifies.

What part of the brain handles short-term memory?

The memory to short term corresponds to the working memory. It allows information to be retained for a relatively short period (a few seconds to a minute). It makes it possible to process information “in the present”. It is managed by the prefrontal cortex and involves different regions near sensory areas. Short-term memory will solicit sensory or perceptual memory. “Thus, a lot of this information will disappear if it is not relevant.“.

What part of the brain manages long-term memory?

Long-term memory is information that we will keep for the long term. It is expressed through different systems: the episodic memory (memories of the past), semantic knowledge (on the world), the procedural memory (know-how) that interact with each other. Semantic memory is underpinned by the temporal poles, “in this case, the seahorses are less stressed“. Finally, procedural memory requires a network of subcortical structures and the cerebellum.

Why do some brains fail to store memory?

The memory storage problem corresponds to oblivion. “Forgetting is first of all beneficial: we will keep what is important according to personal criteria. It is more problematic when it refers to a pathology such as memory diseases, head trauma…”Alzheimer’s disease particularly affects the hippocampi, in the form of atrophic lesions. The patient thus loses his memories of the past and finds it difficult to record new memories.“. In children, the memory storage problem may be related to learning disabilities because his environment is not favorable, because he is stressed… “There are a multitude of reasons why memory is lacking or not functioning optimally.“.

“Memory is constantly evolving: it maintains the information we need according to the constraints of the environment, but also to our aspirations and projects. She is plastic and dynamic“, insists Professor Eustache. To facilitate and improve the storage of information in the brain, it must be in good health: “you need to have a cognitive reserve to have an operational brain”. For this, the following conditions must be optimized: nutritional balance, correct lifestyle, working on your memory “get into the habit of wanting to learn and having positive and stimulating activities”interact with others and learn from others”social relationships facilitate the memorization of information“, and set up an organization that facilitates learning. “You also have to take time for yourself and avoid overstimulation, mental load. To work well, memory needs attention“, he concludes.

Thanks to Prof. Francis Eustache, neuropsychologist at the Inserm Neuropsychology and Imaging of Human Memory laboratory, professor at the École Pratique des Hautes Études, University of Caen; Chairman of the scientific council of the B2V Observatory of Memories.