This amnesia affects episodic memory and makes it impossible to create memories during the very first years of life. Rest assured, it’s completely normal. Here are the mechanisms behind our impossibility to train memories of our first life experience.
The science of memory development
To better understand infantile amnesia, we must first distinguish the different types of memory that develop during our early childhood. The declarative (or explicit) and non -declarative (or implicit) memory is mainly distinguished. The declarative memory concerns conscious storage of concrete facts, events, places or experiences, and is divided into semantic memory (general knowledge on the environment) and episodic memory (memories of events or personal experiences). Non -declarative memory, on the other hand, is unconscious and includes the skills acquired, our habits and our conditioning.
In infants, semantic memory seems to develop before episodic memory. It is by using this form of memory that, from the age of six months, babies can manifest early forms of declarative memory by retaining information about events involving objects and actions, even after a certain period. However, this early knowledge of events remains very rudimentary, fragmented and highly dependent on the indices provided to babies by adults. The ability to recall spontaneously and relive past autobiographical events, characteristic of episodic memory, is not fully developed in very young children.
The role of the hippocampus
If infants and babies fail to create memories, it is partly because their brain is not sufficiently developed. For the training of declarative memories, that is to say specific events and experiences, the hippocampus plays a central role. This is a brain structure located in the median temporal lobe, and it is essential to encode, consolidate and recover memories of the events lived.
In infants, the hippocampus continues to develop significantly after birth. More specifically, the toothed gyrus, part of the hippocampus which connects it to the cortical regions of the brain, reaches its full maturity only after birth. This progressive development of the hippocampus is a factor that limits the formation of the first episodic memories, since this organ continues to develop until the age of about 7 years. This is one of the reasons why our first childhood memories appear only between the age of 3 and 6 years.
Infantile amnesia: a problem of recovery of memories?
Recent research suggests that the increase in infants could be active earlier than we thought, and could play a role in encoding memories even in children under the age of two. A study by Yale has shown that the activity of the hippocampus in infants when a image was presented to them for the first time was correlated at the time spent looking at these same images during a second presentation:
For this study, the researchers wanted to identify a robust means of testing the episodic memory of infants. The team, led by Tristan Yates, used a method of showing infants aged four months to two years the image of a new face, a new object or a new scene. Then, after the babies saw several other different images, the researchers showed them an image already seen next to a new one.
According to the researchers, when babies have only been exposed to an object once, we generally expect them to look at it longer when they see it again. In this type of task, if a baby fixes the image already seen more than that which is new to him, it may indicate that he recognizes her as familiar and that he is able to create a memory.
The strongest encoding activity was observed in the posterior part of the hippocampus, the same area associated with episodic memory in adults. These results were more marked in infants over 12 months, contributing to a more complete understanding of the development of the hippocampus to support learning and memory.
This discovery indicates that the hippocampus could be involved in the formation of episodic memories earlier in the development than we thought before. Memories could therefore be trained very early in life, and researchers are still largely unaware of why the hippocampus does not keep these early memories until adulthood.
What to say to those who “remember” very early events?
Regarding adults who claim to remember very early events, these memories are generally considered to be misleading. They often come from what is called the “family novel”. Indeed, family life is punctuated by important events often told to children over time. We then have the impression of remembering it, but this impression comes mainly from the stories of our loved ones repeated several times, which influence our way of rebuilding these memories.
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